Applied Science, Faculty of
Engineering, School of (Okanagan)
DSpace
UBCO
Razi, Mohd Akif
Master of Applied Science - MASc
University of British Columbia
This research explores the potential of wood ash and basalt powder in developing sustainable, low-carbon cementitious composites. The study evaluates the effectiveness of wood ash as a supplementary cementitious material and basalt powder as a sand substitute in mortar and concrete mixtures. Wood ash was incorporated as a cement replacement, up to 30%, and basalt powder was used to replace the sand by up to 100%. A series of experimental tests were carried out to assess fresh properties, mechanical performance, microstructural characteristics, and durability, including freeze-thaw resistance, chloride penetration, sorptivity, and elevated temperature exposure. Results indicate that increasing wood ash content was detrimental, whereas increasing basalt powder was reported to positively impact the mortar and concrete properties. At optimal replacement levels, wood ash enhances long-term strength due to its pozzolanic activity, while basalt powder improves particle packing, leading to denser concrete. The optimal replacement ratio of wood ash was recorded as 10% in both mortar and concrete mixes. In the case of basalt powder, the optimal replacement was concluded as 100% and 50% in mortars and concrete, respectively. The strength was found to be increased by 60.81% compared to the reference sample after 28 days at 100% substitution of basalt powder as fine aggregate. The strength of mortar and concrete mixes was improved by 25% and 18.2% at 10% wood ash content in addition to basalt powder as sand substitute after 28 days. However, the addition of these materials resulted in reduced workability, requiring appropriate admixtures for practical applications. Besides, incorporating wood ash and basalt powder in concrete production can reduce environmental impact by utilizing industrial waste, lowering carbon emissions, and minimizing the depletion of natural resources. These findings provide valuable insights for researchers and industry professionals seeking sustainable alternatives in modern construction.
BEHAVIOR OF LOW-CARBON CEMENTITIOUS COMPOSITES INCORPORATING WOOD ASH AND BASALT POWDER FOR ENHANCED STRENGTH AND DURABILITY by Mohd Akif Razi A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF APPLIED SCIENCE in THE COLLEGE OF GRADUATE STUDIES (Civil Engineering) THE UNIVERSITY OF BRITISH COLUMBIA (Okanagan) April 2025 © Mohd Akif Razi, 2025 ii The following individuals certify that they have read, and recommend to the College of Graduate Studies for acceptance, a thesis entitled: BEHAVIOR OF LOW-CARBON CEMENTITIOUS COMPOSITES INCORPORATING WOOD ASH AND BASALT POWDER FOR ENHANCED STRENGTH AND DURABILITY submitted by Mohd Akif Razi in partial fulfillment of the requirements of the degree of Master of Applied Science . Dr. Shahria Alam, School of Engineering Supervisor Dr. Rehan Sadiq, School of Engineering Co-Supervisor Dr. Kasun Hewage, School of Engineering Supervisory Committee Member Dr. Mahmudur Fatmi, School of Engineering Supervisory Committee Member Dr. Dimitry Sediako, School of Engineering University Examiner iii Abstract This research explores the potential of wood ash and basalt powder in developing sustainable, low-carbon cementitious composites. The study evaluates the effectiveness of wood ash as a supplementary cementitious material and basalt powder as a sand substitute in mortar and concrete mixtures. Wood ash was incorporated as a cement replacement, up to 30%, and basalt powder was used to replace the sand by up to 100%. A series of experimental tests were carried out to assess fresh properties, mechanical performance, microstructural characteristics, and durability, including freeze-thaw resistance, chloride penetration, sorptivity, and elevated temperature exposure. Results indicate that increasing wood ash content was detrimental, whereas increasing basalt powder was reported to positively impact the mortar and concrete properties. At optimal replacement levels, wood ash enhances long-term strength due to its pozzolanic activity, while basalt powder improves particle packing, leading to denser concrete. The optimal replacement ratio of wood ash was recorded as 10% in both mortar and concrete mixes. In the case of basalt powder, the optimal replacement was concluded as 100% and 50% in mortars and concrete, respectively. The strength was found to be increased by 60.81% compared to the reference sample after 28 days at 100% substitution of basalt powder as fine aggregate. The strength of mortar and concrete mixes was improved by 25% and 18.2% at 10% wood ash content in addition to basalt powder as sand substitute after 28 days. However, the addition of these materials resulted in reduced workability, requiring appropriate admixtures for practical applications. Besides, incorporating wood ash and basalt powder in concrete production can reduce environmental impact by utilizing industrial waste, lowering carbon emissions, and minimizing the depletion of natural resources. These findings provide valuable insights for researchers and industry professionals seeking sustainable alternatives in modern construction. iv Lay Summary Concrete production significantly contributes to global carbon emissions, mainly due to the high energy consumption of cement production. This study investigates an eco-friendly alternative by incorporating waste materials, such as wood ash from timber industries and basalt powder from mining operations, into cementitious composites. By utilizing wood ash as cement replacement and substituting sand with basalt powder, the study aims to create more sustainable and durable mortar and concrete mixtures. The research evaluates various parameters such as fresh properties, mechanical strengths and durability performance. Findings indicate that this approach not only improves strength but also enhances concrete performance under extreme exposures, such as freeze-thaw cycles and elevated temperatures. Additionally, the study supports the circular economy by repurposing industrial by-products, offering a viable solution for sustainable construction while maintaining structural integrity and longevity. v Preface I, Mohd Akif Razi, developed all the contents of this thesis and conducted the relevant experiments under the supervision of Dr. Shahria Alam (University of British Columbia) and Dr. Rehan Sadiq (University of British Columbia). Dr. Kasun Hewage (University of British Columbia) and Dr. Mahmudur Fatmi (University of British Columbia) were on the supervisory committee, providing critical feedback and suggestions for improvement. Major portions of the research findings are planned to be submitted for possible publication in peer-reviewed conference proceedings and technical journals. The author conducted all the experimental tests, interpreted the findings, and composed initial drafts of the articles listed below. Grammarly, a generative AI tool, was used to copyedit and proofread the thesis language. Conference Proceedings: 1) Razi, M. A., Kamali, M., Alam, S., & Sadiq, R. (2022). Affordable wall panels using sustainable waste materials: a review. Modular and Offsite Construction (MOC) Summit Proceedings, 138â145. https://doi.org/10.29173/mocs275. Journal Articles: 1) âAn experimental study on the mechanical and microstructural properties of mortar modified with basalt powder and wood ash,â to be submitted, Construction & Building Materials, Elsevier. 2) âAn experimental study on the mechanical, microstructural, and durability properties of low-carbon concrete modified with basalt powder and wood ash,â to be submitted, Journal of Materials in Civil Engineering, ASCE. vi Table of Contents Abstract ......................................................................................................................................... iii Lay Summary ............................................................................................................................... iv Preface .............................................................................................................................................v Table of Contents ......................................................................................................................... vi List of Tables ..................................................................................................................................x List of Figures ............................................................................................................................... xi List of Abbreviations ................................................................................................................. xiii Acknowledgements ......................................................................................................................xv Dedication ................................................................................................................................... xvi Chapter 1: Introduction ..................................................................................................... 1 1.1 Background ................................................................................................................. 1 1.2 Research Gap .............................................................................................................. 5 1.3 Research Objectives .................................................................................................... 6 1.4 Research Significance ................................................................................................. 7 1.5 Research Methodology ............................................................................................... 8 1.6 Thesis Organization .................................................................................................... 8 1.7 Summary ................................................................................................................... 10 Chapter 2: Literature Review .......................................................................................... 12 2.1 General ...................................................................................................................... 12 2.2 Basalt Powder ........................................................................................................... 18 2.2.1 Effects of Using Basalt Powder ........................................................................ 19 2.2.1.1 Mechanical Strengths (Compressive, Flexure, Tensile) ............................... 19 2.2.1.2 Durability Properties ..................................................................................... 21 2.2.1.3 Microstructural Properties ............................................................................ 23 vii 2.3 Wood Ash ................................................................................................................. 29 2.3.1 Effects of Using Wood Ash .............................................................................. 29 2.3.1.1 Mechanical Strengths (Compressive, Flexure, Tensile) ............................... 30 2.3.1.2 Durability Properties ..................................................................................... 32 2.3.1.3 Microstructural Properties ............................................................................ 34 2.4 Effects of Mixing Water Temperature ...................................................................... 42 2.5 Summary ................................................................................................................... 43 Chapter 3: Mix Design and Experimental Testing ........................................................ 44 3.1 General ...................................................................................................................... 44 3.2 Materials ................................................................................................................... 44 3.2.1 Characterization of Wood Ash.......................................................................... 46 3.2.2 Characterization of Basalt Powder .................................................................... 47 3.2.3 Gradation of Aggregates ................................................................................... 50 3.3 Mix Design of Mortar ............................................................................................... 51 3.4 Mix Design of Concrete ............................................................................................ 54 3.5 Sample Preparation ................................................................................................... 55 3.5.1 Mortar Specimens ............................................................................................. 55 3.5.2 Concrete Specimens .......................................................................................... 56 3.6 Experimental Testing ................................................................................................ 59 3.6.1 Mortar ............................................................................................................... 59 3.6.1.1 Flow Value Test ............................................................................................ 59 3.6.1.2 Mechanical Properties ................................................................................... 60 3.6.1.2.1 Compressive Strength ............................................................................. 60 viii 3.6.1.2.2 Flexural Strength ..................................................................................... 61 3.6.1.3 Microstructural Properties ............................................................................ 62 3.6.2 Concrete ............................................................................................................ 63 3.6.2.1 Fresh Properties ............................................................................................ 63 3.6.2.2 Hardened Properties ...................................................................................... 64 3.6.2.2.1 Compressive Strength ............................................................................. 64 3.6.2.2.2 Flexural Strength ..................................................................................... 65 3.6.2.2.3 Splitting Tensile Strength ....................................................................... 66 3.6.2.3 Durability Properties ..................................................................................... 68 3.6.2.3.1 Freeze-Thaw ........................................................................................... 68 3.6.2.3.2 Rapid Chloride Ion Penetration Test ....................................................... 69 3.6.2.3.3 Sorptivity................................................................................................. 71 3.6.2.3.4 Elevated Temperature ............................................................................. 72 3.6.2.4 Microstructural Properties ............................................................................ 73 3.7 Summary ................................................................................................................... 74 Chapter 4: Results and Discussions................................................................................. 75 4.1 General ...................................................................................................................... 75 4.2 Mortar ....................................................................................................................... 75 4.2.1 Flow Value ........................................................................................................ 75 4.2.2 Mechanical Properties ....................................................................................... 79 4.2.2.1 Compressive Strength ................................................................................... 79 4.2.2.2 Flexural Strength ........................................................................................... 84 4.2.3 Microstructural Properties ................................................................................ 85 ix 4.3 Concrete .................................................................................................................... 92 4.3.1 Fresh Properties ................................................................................................ 92 4.3.2 Hardened Properties .......................................................................................... 93 4.3.2.1 Compressive Strength ................................................................................... 93 4.3.2.2 Flexural Strength ........................................................................................... 94 4.3.2.3 Splitting Tensile Strength ............................................................................. 96 4.3.2.4 Failure Patterns ............................................................................................. 96 4.3.3 Durability Properties ......................................................................................... 98 4.3.3.1 Freeze-Thaw Exposure ................................................................................. 98 4.3.3.2 Rapid Chloride Ion Penetration Test ........................................................... 101 4.3.3.3 Sorptivity..................................................................................................... 102 4.3.3.4 Elevated Temperature Exposure ................................................................. 103 4.3.4 Microstructural Properties .............................................................................. 104 4.4 Summary ................................................................................................................. 107 Chapter 5: Conclusions and Recommendations .......................................................... 110 5.1 General .................................................................................................................... 110 5.2 Conclusions ............................................................................................................. 110 5.3 Outcomes and Contributions................................................................................... 112 5.4 Limitations .............................................................................................................. 113 5.5 Recommendations for Future Research .................................................................. 114 Bibliography ...............................................................................................................................116 x List of Tables Table 2.1 List of previous studies involving basalt powder in cement paste, mortar and concrete mixes ............................................................................................................................................. 24 Table 2.2 List of previous studies incorporating wood ash in cement paste, mortar and concrete mixes ............................................................................................................................................. 35 Table 3.1 Material properties of aggregates ................................................................................. 46 Table 3.2 Chemical composition of wood ash ............................................................................. 47 Table 3.3 Chemical composition of basalt powder ....................................................................... 49 Table 3.4 Basalt as sand replacement ........................................................................................... 53 Table 3.5 Basalt as cement replacement ....................................................................................... 53 Table 3.6 Wood ash as cement replacement and basalt powder as fine sand replacement .......... 54 Table 3.7 Mortar mixes prepared using hot mixing water ............................................................ 54 Table 3.8 Mix proportions of concrete ......................................................................................... 55 Table 3.9 Experimental program for concrete specimens ............................................................ 57 Table 3.10 Specimens prepared in each batch .............................................................................. 59 Table 3.11 Mortar mixes for flow value test ................................................................................. 60 Table 4.1 Flow values of various mortar mixes ............................................................................ 77 Table 4.2 Fresh properties of concrete .......................................................................................... 92 xi List of Figures Figure 1.1 Geological map of Canada with various rock deposits ................................................ 3 Figure 1.2 Geological map of Canada with forest area ................................................................. 4 Figure 1.3 Thesis organization ...................................................................................................... 11 Figure 2.1 Life cycle of accidental fire ........................................................................................ 14 Figure 2.2 Various fire curves available in literature .................................................................. 15 Figure 2.3 Concrete behavior under high temperature ................................................................ 17 Figure 3.1 Constituents of concrete .............................................................................................. 45 Figure 3.2 Admixtures used in the concrete ................................................................................. 45 Figure 3.3 XRD pattern of basalt powder ..................................................................................... 49 Figure 3.4 TGA curve of basalt powder ....................................................................................... 50 Figure 3.5 Gradation of aggregates ............................................................................................... 51 Figure 3.6 Casting of mortar specimens ....................................................................................... 56 Figure 3.7 Flow value test apparatus ............................................................................................ 60 Figure 3.8 Test setup for compressive strength of mortar ............................................................ 61 Figure 3.9 Test setup for flexural strength of mortar .................................................................... 62 Figure 3.10 SEM and EDS test setup............................................................................................ 63 Figure 3.11 Compressive strength of concrete ............................................................................. 65 Figure 3.12 Flexural strength of concrete ..................................................................................... 66 Figure 3.13 Test setup for splitting tensile strength of concrete ................................................... 67 Figure 3.14 Freeze-thaw cabinet ................................................................................................... 69 Figure 3.15 Freeze-thaw cycle ...................................................................................................... 69 Figure 3.16 Rapid chloride ion penetration test setup .................................................................. 71 xii Figure 3.17 Sorptivity test setup ................................................................................................... 72 Figure 3.18 Elevated temperature test .......................................................................................... 73 Figure 4.1 Flow diameters of various mortar mixes ..................................................................... 78 Figure 4.2 7-day wet samples of mortar mixes ............................................................................. 81 Figure 4.3 Compressive strength of mortar mixes ........................................................................ 83 Figure 4.4 Broken samples of BAC 20 while demolding ............................................................. 85 Figure 4.5 Flexural strength of mortar mixes at 28 days .............................................................. 85 Figure 4.6 SEM-EDS of mortar mixes using basalt as sand replacement .................................... 88 Figure 4.7 SEM-EDS of mortar mixes using basalt as cement replacement ................................ 89 Figure 4.8 SEM-EDS of mortar mixes with varying mixing water temperatures ........................ 90 Figure 4.9 SEM-EDS of mortar mixes with varying mixing water temperatures ........................ 91 Figure 4.10 Compressive strength of various concrete mixes ...................................................... 94 Figure 4.11 Flexural strength of concrete mixes at 28 days ......................................................... 95 Figure 4.12 Splitting tensile strength of concrete mixes at 28 days ............................................. 96 Figure 4.13 Compressive failure modes of various concrete mixes at 28 days ............................ 97 Figure 4.14 Deterioration of freeze-thaw specimens after 150 cycles ........................................ 100 Figure 4.15 Residual flexural strength after 150 F-T cycles ...................................................... 101 Figure 4.16 Change in mass after 150 F-T cycles ...................................................................... 101 Figure 4.17 Chloride ion penetration in concrete mixes ............................................................. 102 Figure 4.18 Sorptivity of concrete mixes .................................................................................... 103 Figure 4.19 Residual compressive strength of concrete at elevated temperatures ..................... 104 Figure 4.20 % reduction in compressive strength of concrete at elevated temperatures ............ 104 Figure 4.21 SEM-EDS of various concrete mixes ...................................................................... 107 xiii List of Abbreviations ACI American Concrete Institute Al2O3 Aluminum Oxide AEA Air Entraining Admixture ASTM American Society for Testing and Materials CaCO3 Calcium Carbonate Ca(OH)2 Calcium Hydroxide CH Calcium Hydroxide CMHC Canada Mortgage and Housing Corporation CO2 Carbon Dioxide CSA Canadian Standards Association CSH Calcium Silicate Hydrate EDS Energy Dispersive Spectroscopy Fe2O3 Iron Oxide F-T Freeze-Thaw GUL General Use Limestone HRWRA High Range Water Reducing Admixture ITZ Interfacial Transition Zone NaCl Sodium Chloride NaOH Sodium Hydroxide NRCan Natural Resources, Canada RCPT Rapid Chloride Ion Penetration Test SCM Supplementary Cementitious Material xiv SEM Scanning Electron Microscopy SiO2 Silicon Dioxide TGA Thermogravimetric Analysis UHPC Ultra-High-Performance Concrete XRD X-Ray Diffraction XRF X-Ray Fluorescence xv Acknowledgements I would like to express my heartfelt gratitude to my supervisor, Dr. Shahria Alam, for his continuous support and push towards learning throughout the research. I feel privileged to have the opportunity to be a part of his research group and work under a supervisor equipped with immense knowledge, expertise, and intellect. I am highly indebted to my co-supervisor, Dr. Rehan Sadiq, for his kind guidance, unending motivation, and positive feedback throughout my studies at UBC Okanagan. Besides being my mentor, he has also been an inspiration to me in terms of time management and being a well-organized human being. This thesis would not have been possible without his precious time and insightful input. I am also grateful to my supervisory committee members, Dr. Kasun Hewage and Dr. Mahmudur Fatmi, for their participation and for reviewing my thesis work. My sincere thanks to my senior and postdoctoral fellow, Dr. Salim Khoso, for his valuable suggestions regarding the experiments and for reviewing my thesis work. I want to acknowledge and thank my friends Kwan Zhen Lee, Saif Ahmad Alvi, Meraj Rubayat Kamal, and Mustafa Mansoor for their kind help in the lab. My special thanks to the lab technicians at UBC Okanagan, especially Kim Nordstorm and Eric Ristau, for their generous support in the lab. Also, I would like to express appreciation to Lafarge, Sika, Canlava and Kelowna Ready Mix for their kind donations of material supplies to conduct this study. xvi Dedication âDedicated to my cherished well-wishers and beloved onesâ1 Chapter 1: Introduction 1.1 Background Climate change is a pressing global concern driven by greenhouse gas emissions, primarily carbon dioxide (CO2) (United States Environmental Protection Agency, 2025). The climate crisis is evident by weather anomalies worldwide, such as extreme heat conditions resulting in severe drought and frequent forest fires and atmospheric river conditions causing devastating flash floods. Scientists and researchers have suggested that the impacts of climate change would be exacerbated if the carbon footprint is not controlled on time. According to the World Metrological Organization, global CO2 emissions have increased by 11.4% over the past two decades (WMO, 2024). The construction industry is one of the biggest contributors to the carbon footprint, accounting for about 37% of global emissions (United Nations Environment Programme, 2023). Concrete, the most widely used construction material, is produced more than 4.2 billion tonnes annually worldwide (Global Cement and Concrete Association, 2020). Cement is a key constituent of concrete that provides strength to the concrete mix. Although cement constitutes only 10-15% of the matrix, it is responsible for approximately 7% of the greenhouse gas emissions globally. Cement manufacturing in Canada emits approximately 9.7 metric tonnes of CO2 annually, accounting for 1.4% of the countryâs total emissions (Cement Association of Canada, 2021). Along this vein, the government of Canada has announced that it will accomplish net-zero emissions by the year 2050 by promoting clean technologies to decrease emissions in all economic sectors, including the construction industry. In recent years, Canada has witnessed many extreme weather events, such as forest fires and floods, resulting in the loss of livelihood and property. The forest fires in Banff, Alberta (2024), West Kelowna, British Columbia (2023), Halifax, Nova Scotia (2023), Fort McMurray (2016), and flash floods in Toronto, Ontario (2024), Montreal, Quebec 2 (2024), Halifax, Nova Scotia (2023) and Merritt, British Columbia (2021) are some of the recent examples of intense weather events that caused forced evacuations and infrastructure destruction amounting multimillion-dollar loss to Canadian economy. To mitigate the impacts of climatic disasters, the National Research Council, Canada, has announced the modification of building codes and design standards with greener and climate-resilient construction practices. Population growth significantly influences infrastructure development, particularly in urban areas. According to the United Nations World Population Prospects (2024), the world population is estimated to reach around 10 billion by 2050. The population of Canada is also expected to increase by more than 56% in the next 25 years (Statistics Canada, 2025). The construction industry would experience considerable infrastructure strain with the population influx, causing further environmental degradation. The Canada Mortgage and Housing Corporation (CMHC), (2023) assessed that Canada will require 3.5 million new housing units by 2031. Besides, skyrocketing housing prices and the meager income of major demographic clusters have engendered the housing affordability crisis. According to the Canadian Housing Survey (2023) conducted by CMHC, around 11% of the population has inadequate housing needs and is vulnerable to chronic homelessness. The government of Canada has launched a National Housing Strategy to meet the housing needs by building new affordable houses, modernizing the existing ones, and alleviating the gap between supply and demand. Canada has enormous natural resource reserves, including rocks, minerals, and forests. Figure 1.1 and Figure 1.2 show the deposits of various rocks, and the forest cover expanded throughout Canada (NRCan, 2023). The mining industry of Canada produces approximately 650 million tonnes of waste rock and tailings annually (Mining Watch Canada, 2024). Most of the mining waste is dumped into landfills, posing a serious hazard to the environment. On the other hand, the 3 forest area of Canada spans around 367 million hectares (NRCan, 2023), covering 35% of the country's area and accounting for 9% of global forests (Statistics Canada, 2025). The global shift towards sustainability has increased the demand for renewable resources such as timber. The processing of a standing tree into timber generates a waste of about 31.2% by volume (Jenkins., 1933). The waste generated is classified into two categories: a) forest harvest residues (treetops, branches, and leaves) and b) sawmill residues (i.e., chips, sawdust, shavings, and bark) (Krigstin et al., 2012). The sawmill residues are used as a biofuel for power production in sawmills, yielding wood ash as a final by-product (Hannam et al., 2018). Approximately 70% of the wood ash produced is dumped into landfills, again posing a serious hazard to the environment (Siddique, 2012). Figure 1.1 Geological map of Canada with various rock deposits (NRCan, 2023) 4 Figure 1.2 Geological map of Canada with forest area (NRCan, 2023) At the same time, the Government of Canada, in collaboration with the Cement Association of Canada, is exploring alternatives to decarbonize the construction sector, promoting greener technologies and a circular economy on its pathway to net zero emissions by 2050. Developing concrete engineered with supplementary cementitious materials (SCMs) has the potential to mitigate the aforementioned problems (NRCan, 2023). It is also known as Low-Carbon Concrete due to the reduced embodied emissions. Integrating waste products from the mining and timber industry into the development of low-carbon concrete can help alleviate the environmental impacts by reducing natural resource depletion, carbon footprint, and landfill hazards. Additionally, it fosters the circular economy by recycling waste products and endorses affordability by cutting material costs. 5 1.2 Research Gap The durability and versatility of concrete have made it indispensable in modern infrastructure. However, the high environmental cost of its production necessitates urgent innovation. At the same time, there is also a pressing need for the climate resilient infrastructure to embrace climate change impacts such as forest fires and flash floods. SCMs and alternative aggregates derived from industry by-products offer promising solutions to mitigate the environmental impact of concrete production in addition to strength and durability enhancement. Research studies have been carried out on individual SCMs and aggregate replacements, such as fly ash, silica fume, quarry dust, etc. Among these, wood ash and basalt powder are emerging as viable options. Basalt is a thermally stable material, so it could be a viable solution for developing concrete with good fire resistance. Since cement production is a major contributor to carbon emissions, replacing cement with SCMs such as coal fly ash due to its pozzolanic properties could reduce its environmental impact. However, to achieve the net zero emission goals, coal power plants have been shutting down worldwide to achieve zero emissions, resulting in a dearth of coal fly ash. In search of new cementitious materials with pozzolanic properties, wood ash could be a potential alternative. However, there is limited literature and knowledge apropos to the combined influence of wood ash and basalt powder in concrete. By taking into account these factors, the specific gaps are presented below. Combined Application: Most research studies focused either on wood ash as a supplementary cement replacement or basalt powder as a fine aggregate substitute. The wood ash was utilized as a SCM upto 100% and basalt powder was substituted upto 100% as sand replacement in the previous studies. However, the 6 combination of these two materials, particularly their synergistic effects on mechanical and durability properties, is less explored. Performance Under Extreme Conditions: There is a lack of comprehensive research on how wood ash and basalt powder impact concrete performance under challenging ambient conditions, such as deterioration due to the volumetric changes caused by freezing of pore water when exposed to F-T cycles, spalling mechanism due to the pore pressure buildup caused by the evaporation of absorbed water and damage caused by the acid attack such as chloride penetration. Replacement of Materials Level: The influence of wood ash and basalt powder on cementitious composites depends on their source, composition, and various replacement levels. Understanding this variability of replacement levels is crucial for standardizing their use in concrete applications, especially for resilient infrastructure. 1.3 Research Objectives This study primarily focuses on developing concrete with enhanced strength and durability, specifically with improved resistance against high temperatures and reduced environmental impacts. Along this vein, wood ash was utilized as an SCM at various replacement levels and basalt powder as a sand substitute, which are environmentally friendly alternatives to conventional cement and aggregates, respectively. To achieve this goal, the specific objectives include: 1) Determine the behavior of cement mortar and concrete by incorporating wood ash and basalt power into cementitious composites under regular and high temperature exposure. 2) Identify the optimal replacement ratios of wood ash as a cement replacement and basalt powder as a sand substitute. 7 3) Investigate the influence of wood ash and basalt powder on the durability of concrete under extreme conditions. 1.4 Research Significance Wood ash is a by-product of timber, which exhibits pozzolanic properties that enhance the long-term strength and durability of cementitious systems (Ramos et al., 2013). Similarly, basalt powder, derived from quarrying operations, can serve as fine aggregate replacement, improving the packing density and microstructural characteristics of concrete (Dobiszewska et al., 2018). While these materials have been studied individually, to the best of the authorâs knowledge, their combined application and effect of wood ash as an SCM and basalt powder as a sand substitute in mortar and concrete mixes remains largely unexplored. This research is significant for several reasons: i. Environmental Impact: By integrating wood ash and basalt powder into concrete, the study aims to diminish the carbon footprint of construction while promoting the recycling of industrial by-products. ii. Economic Benefits: Utilizing locally available waste materials can lower construction costs, especially in regions where conventional SCMs and aggregates are scarce or expensive. iii. Climate Resilience: The study investigates the performance of these materials under extreme conditions, including high temperatures, freeze-thaw (F-T) cycles, and chloride exposure, contributing to the development of durable, climate-resilient infrastructure. Furthermore, based on the experimental findings, this study bridges the gap between sustainability and functionality, offering a pathway for the construction industry to align with global sustainability goals and finally providing guidelines for climate-resilient infrastructure. 8 1.5 Research Methodology This study was carried out in three phases to achieve the defined objectives. Phase 1 involved a comprehensive literature review on the effects of using basalt powder and wood ash on various properties of mortar and concrete mixes to identify the appropriate replacement type and optimum replacement levels. Phase 2 consisted of utilizing basalt powder as cement and sand substitute in mortar mixes in varying proportions based on the literature to determine the suitable substitution type and proportion of basalt powder. Furthermore, the introduction of wood ash as cement replacement in combination with basalt powder as a sand substitute in mortar mixes was investigated to assess its influence on the fresh, mechanical, and microstructural properties. The replacement levels of wood ash were considered based on literature, whereas the substitution ratio of basalt powder was determined from the first part of phase 2 results. Phase 3 constitutes the incorporation of wood ash and basalt powder in concrete mixes as cement and sand replacement, respectively, to evaluate its effects on durability properties in addition to the fresh, mechanical, and microstructural properties. The replacement values of wood ash and basalt powder were governed by phase 2 results. 1.6 Thesis Organization This thesis comprises five chapters with a key focus on wood ash and basalt powder, from the contextual background, their applications in resilient infrastructure, experimental findings and practical recommendations, as shown in Figure 1.3. An overview of the chapters is provided below. Chapter 1: Introduction The first chapter provides the foundational framework for this research study. It begins with the background, outlining the environmental concerns triggered by the construction industry and the 9 potential of alternative materials to mitigate these impacts. The chapter also emphasizes the researchâs significance by linking the utilization of wood ash and basalt powder to sustainability goals and climate-resilient infrastructure. The research gap is identified to highlight the novelty of combining these materials in concrete. Clear objectives are established to guide the investigation, and an overview of the thesis organization is provided to prepare the reader for subsequent chapters. Chapter 2: Literature Review This chapter provides a comprehensive literature review of the existing studies relevant to the research. It explores the properties and applications of wood ash and basalt powder, emphasizing their role as SCMs and fine aggregate replacement, respectively. Additionally, it discusses the performance of these materials in concrete under various mechanical and durability conditions, such as compressive strength, F-T resistance, and chloride penetration. The chapter identifies gaps in literature, particularly the lack of research on the combined use of wood ash and basalt powder, thus reinforcing the need for this study. Chapter 3: Materials and Methods The third chapter outlines the experimental approach and methodology used to achieve the research objectives. It describes the characterization of materials, including wood ash and basalt powder, detailing their chemical and physical properties. The chapter also specifies the mix design proportions of mortar and concrete mixes as well as the procedures for testing mechanical properties such as compressive, tensile, and flexural strengths and durability properties such as water absorption, chloride penetration, and F-T resistance. The methodologies are designed to systematically evaluate the feasibility and performance of the proposed sustainable concrete mixtures. 10 Chapter 4: Results and Discussion This chapter presents and interprets the findings of the experimental study. It provides a detailed analysis of how wood ash and basalt powder influence the mechanical and durability properties of concrete. The results are compared to conventional mixes to assess the effectiveness of these materials. Additionally, the chapter discusses the synergy between wood ash and basalt powder, highlighting their combined impact on the microstructural and performance aspects of concrete. The findings are critically analyzed in the context of research objectives, offering insights into practical applications. Chapter 5: Conclusions and Recommendations The final chapter concludes the study by summarizing the key findings and contributions. It highlights how the combination of wood ash and basalt powder addresses the research gap and advances sustainable construction practices. Practical recommendations are provided for the use of these materials in real-world applications, focusing on optimal replacement levels and performance considerations. The chapter also outlines the limitations of this study and proposes directions for future research to explore further the potential of these materials in diverse environmental and structural contexts. 1.7 Summary This chapter described the environmental and affordability concerns associated with the construction sector and the hazards posed by the timber and mining industry. The curtailment of emissions and the need for cheaper housing alternatives highlighted the necessity for this study. Further, the research gaps and significance were elucidated to identify a possible solution to the aforementioned concerns. Developing low carbon cementitious composite harnessed by the 11 combined application of wood ash and basalt powder was determined as a holistic approach to mitigate these concerns. Besides, a set of objectives was defined to assist in the development of low carbon cementitious composite. The research methodology adopted to meet the well-defined objectives was also discussed. Lastly, a thesis organization exhibiting a summary of all the chapters was illustrated to provide a general idea about this study. Figure 1.3 Thesis organization 12 Chapter 2: Literature Review 2.1 General This chapter provides a detailed discussion of the impact of F-T cycles, chloride attack, and high-temperature exposure on conventional concrete. Further, a comprehensive overview of the previous studies incorporating basalt powder and wood ash in cementitious composites is illustrated. The effects of using basalt powder and wood ash individually on mechanical strengths, durability and microstructural properties are also discussed in the following sections. Concrete is one of the most commonly utilized construction materials in civil infrastructure systems, such as buildings, bridges, and roads, due to its inherent strength and durability. However, its performance is often compromised under extreme environmental conditions, including accidental fires, F-T cycles, chloride exposure, and flash floods. Among these, repeated F-T cycles pose a significant challenge, particularly in cold regions. As defined by the American Concrete Institute (ACI), the weather is classified as cold when the average daily temperature remains under 40°F (5°C) for three consecutive days (ACI Committee 306, 2010). To prevent concrete from weathering degradation in cold weather regions, ACI 318 and CSA A23.1 limit the water-cement ratio to a maximum of 0.45. It also specifies the minimum compressive strength at 28 days to be 31MPa and 32 MPa, respectively. Besides, ACI 318 and CSA A23.1 also recommend a minimum air content of 4.5-6% and 5-8% for concrete exposed to deicing salts and F-T cycles. The pore size distribution, porosity, and air voids play a pivotal role in defining the magnitude of concrete deterioration under F-T cycles (Luo et al., 2018) and chloride attack. A low water-binder ratio can lower the capillary porosity and, thus, the ingress of external moisture into the concrete pores. However, low-permeable concrete is more prone to internal cracking caused by the stresses 13 induced by rapid ice formation. The temperature fluctuation causes the absorbed moisture in a fully saturated concrete to crystallize under frost action and, therefore, increases the internal pore pressure due to volumetric changes, followed by the rupture of pores to micro-cracks, particularly in interfacial transition zones (ITZ) (Luo et al., 2018). The intensity and size of cracks amplify with the subsequent F-T cycles, causing further water ingress and ultimately resulting in concrete failure (Khanfour & El Refai, 2017). On the other hand, the air entrainment of concrete helps to alleviate internal frost damage as non-air-entrained concrete is more vulnerable to instant ice formation, resulting in internal cracking and coarse aggregate elimination (Liu & Hansen, 2016). The air entrainment equips the concrete with closely spaced air bubbles to act as stress sinks. If the concrete has an adequate air-void system, the unfrozen water moves away from the ice-filled pores toward the air-filled voids, where the water can freeze freely without developing large stresses (Wakimoto et al., 2008). The detrimental effects of F-T action are further exacerbated by the chloride exposure of concrete due to the use of deicing salts (Matalkah & Soroushian, 2018). The application of de-icing salts in cold climates instigates salt scaling on concrete surfaces and consequently damages the concrete cover, followed by the corrosion of reinforcement (Zahedi et al., 2022). The phenomenon of salt scaling is defined as the erosion of very small pieces of cementitious matrix from the concrete surface due to the temperature gradient between the ice/brine layer and the concrete surface (Valenza & Scherer, 2006). Salt scaling is most destructive at an intermediate or pessimum concentration of solute, i.e., 3% by weight (Wakimoto et al., 2008). At lower concentrations, the tensile stresses due to thermal mismatch cannot exceed the tensile strength of the ice, and higher concentrations of solute prevent the development of tensile stresses by melting the ice (ÃopuroÇ§lu & Schlangen, 2008). 14 The extent of damage to any concrete structure in case of fires depends on various factors such as fire exposure duration, peak temperature, and type of concrete. At low temperatures, concrete has some fire resistance up to a certain time limit. However, the performance of concrete under high temperatures for longer periods can cause thermal cracking, spalling of the surface layer, and, eventually, failure of the structural system. Numerous studies have been conducted to investigate the performance of concrete subjected to elevated temperatures or fires (Khoso, 2021). Researchers have also introduced the nominal fire curves in the building codes and guidelines such as ASTM E119 (2020) and ISO 834 (2014) to embrace in advance against any accidental fire threat. However, these nominal fire curves are conservative for structural fire safety as they are based on experimental fires and do not consider the decay phase of the actual accidental fires (Pulkit & Adhikary, 2022). The life cycle of actual world fires can be categorized into three different phases, as presented in Figure 2.1: growth phase, when the fire ignites and there is a linear increase in temperature with the fire escalation; a steady phase, when the fire temperature remains constant following a flashover and decay phase when the fire intensity reduces due to oxygen scarcity after fuel consumption. Figure 2.1 Life cycle of accidental fire (Pulkit & Adhikary, 2022) 15 Besides, the fire response of concrete also depends on the usage of the building, whether it is a residential building such as a house or a commercial building such as a tire factory, because concrete under high temperatures is subjected to changes in material performance with respect to surrounding temperatures. Figure 2.2 represents different fire scenarios that can be used to analyze and design concrete structures. Fire I represents a severe fire, such as a tire factory where the temperature goes beyond 1200°C due to the burning of factory materials. In contrast, Fire II represents a fire of less intensity, such as a house where the temperature can hardly reach up to 700°C. It is also evident from Figure 2.2 that the nominal fire curves in building codes and guidelines such as ASTM E119 (2020) do not take into account the decay phase as shown in Fire I and Fire II. In the decay phase, the cooling down of fire allows the concrete to regain some of its strength; however, this recovery is limited and depends on several factors, including the peak temperature attained during the fire and the duration of exposure. Reinforcement plays a crucial part in maintaining the structural integrity of concrete during and after a fire. The residual strength of concrete is influenced by the reinforcement, but the concrete itself may not fully regain its original strength (Gernay & Bamonte, 2022). Figure 2.2 Various fire curves available in literature (Pulkit & Adhikary, 2022) 16 Concrete is a mix of fine aggregate, coarse aggregate, binding material and water. When the binding material, such as cement, reacts with water, it produces CSH (Calcium Silicate Hydrate) gel, which provides bond strength to the aggregates. The behavior of concrete under high temperatures is illustrated in Figure 2.3. When the concrete is subjected to elevated temperatures, the free moisture and chemically bonded water in CSH start dehydrating beyond 100°C, weakening the bond between the cement paste and the aggregates. When the temperature exceeds 200°C, there is a probability of spalling of the surface layer because the vaporized moisture content in concrete tries to move out. However, the dense microstructure of concrete prevents its movement, and this develops a temperature difference, resulting in a saturated layer. Nevertheless, moisture from interior layers still tries to come out, causing a buildup of pore pressure. This buildup pressure can be dissipated only with the dispersion of interior moisture vapor. Continuous heating and movement resistance will further increase the pore pressure. When this pore pressure exceeds the tensile capacity of concrete, it will result in the explosive spalling of concrete. When the temperature reaches 300°C, minor cracks are visible due to the internal stresses induced by the thermal expansion of aggregates. The shrinkage of concrete initiates at a temperature of more than 400°C due to the dissociation of Calcium Hydroxide Ca(OH)2, further amplifying the surface cracking. When the temperature is above 500°C, the physical and microstructural changes in concrete become more evident and almost irreversible. At a temperature of about 600°C, the CSH gel starts dissociating, resulting in the weakening of the bonds between various constituents of concrete, causing an overall loss of strength. The Calcium Carbonate (CaCO3), which contributes towards the hardening and durability of concrete, starts degrading around 700°C. On further exposure to higher temperatures beyond 800°C, there is a sharp increase in the disintegration of concrete with large surface cracks due to the absolute loss of hydration water. As a result, concrete 17 crumbles and can no longer support any load, ultimately losing its strength and durability (Hertz, 2005). Figure 2.3 Concrete behavior under high temperature (Lahoti et al., 2019) The aggregate type also influences concrete's physical properties under high temperatures. Siliceous aggregates cause more damage than granite, basalt, limestone, and sea gravel due to their high coefficient of thermal expansion (Hertz, 2005). A high coefficient of thermal expansion causes a larger expansion in the material when exposed to high temperature and, subsequently, produces internal thermal stresses, thus causing the development of cracks and strength reduction. Previous studies observed that the spalling of concrete at elevated temperatures reduces the cross-sectional area of the structural component and, subsequently, diminishes the load-carrying capacity, resulting in the failure or collapse of the structure (Ghiji et al., 2022). Therefore, the fire endurance of concrete can be enhanced if concrete spalling can be prevented or reduced. Calcareous aggregates such as limestone perform better than siliceous aggregates as they decompose at a higher temperature and, hence, delay the spalling of the surface layer of concrete 18 (Ma et al., 2015). Besides, the performance of concrete when exposed to fires is significantly influenced by the constituents of concrete. Literature indicates that concrete with higher endurance against fire can be produced by applying intumescent coatings such as paints, sprays, linings or mortars on the concrete surface or by adding SCMs with fire retarding properties such as fly ash, slag, silica fumes, metakaolin, polypropylene fibres, basalt powder etc as a replacement of different constituents of concrete in varying proportions (Khoso et al., 2016). In the present study, the effect of basalt powder and wood ash on the fresh, mechanical, durability and microstructural properties of mortar and concrete mixtures was assessed in four phases. Basalt powder was first utilized as cement replacement, followed by sand replacement in mortar mixes. Further, basalt powder was introduced as a fine aggregate replacing natural sand with wood ash as an SCM in mortar and concrete mixes. 2.2 Basalt Powder Basalt, a volcanic rock, has significant potential as a SCM due to its pozzolanic activity (Yu et al., 2020). However, the source, type, and pozzolanic content of basalt determines the feasibility of its application as SCM, fine aggregate, or mineral additive in mortar or concrete mixes (Sharaky et al., 2022). For a material to qualify as a pozzolanic additive, the combined content of Silicon dioxide (SiO2), Aluminum Oxide (Al2O3), and Iron Oxide (Fe2O3) must exceed 70%, as per ASTM C618 (2023). These criteria ensure that basalt can effectively contribute to the hydration process and enhance concrete properties. In this study, the basalt powder used in experimental work was sourced from a stone quarry. According to Dobiszewska & Barnes (2020a), the waste powder or dust generated during rock extraction possesses the same mineral and chemical composition as the parent basalt rock, making it suitable for use in mortar or concrete mixes. 19 2.2.1 Effects of Using Basalt Powder Previous studies regarding basalt powder have incorporated it as SCM or cement replacement, as fine aggregate or sand replacement and as coarse aggregate in binary mixtures, and as a mineral additive in combination with other SCMs such as fly ash, pumice, silica fume, and barite in ternary mixtures as shown in Table 2.1. The effects of using basalt on various mechanical, durability and microstructural properties of mortar and concrete mixes are discussed below. 2.2.1.1 Mechanical Strengths (Compressive, Flexure, Tensile) The incorporation of basalt powder, either as a cement or sand replacement, significantly influences the mechanical properties such as compressive, flexural, or tensile strengths. El-Didamony et al. (2015) examined the pastes prepared with cement and basalt powder and observed the highest compressive strength at a 20% replacement level. A similar increase in compressive and flexural strengths was obtained by Dobiszewska & Beycioǧlu (2017) in mortars with the addition of basalt powder as a cement substitute up to 8% by mass. However, Dobiszewska et al. (2018) observed a reduction in compressive and flexural strengths with an increment of basalt powder content while investigating the pastes and mortars with (0-40%) and (0-20%) replacement levels by mass of cement. They attained a reduced compressive strength for all the mixes at all ages due to cement dilution. On the contrary, flexural strength was low at early ages, but it increased by 7% and 6% at 90 days and 180 days, respectively. Similarly, Laibao et al. (2013) also reported that the addition of basalt powder replacing cement resulted in a drop in compressive strength after 28 days. Regardless of low early strength due to slow pozzolanic reaction, they found compressive strength after 90 and 128 days comparable to the control paste. In another study, Dobiszewska & Barnes (2020a) utilized basalt powder as a fine aggregate. They reported that up to 20% of sand replacement with basalt powder increased the compressive and flexural strengths 20 of mortar by 25 % and 22%, respectively, after 90 days. Amin et al. (2020) replaced cement with basalt powder in different proportions from 0-40% in Portland cement mortars and obtained an optimum replacement level of 10%. Similarly, Türk et al. (2022) studied the influence of basalt powder in varying percentages (5-50% by mass) as SCM on the mechanical properties of self-compacting mortars and concluded that long-term compressive and flexural strength of mortars with 10% basalt powder was similar to the control mortar. Dobiszewska et al. (2018) replaced sand with basalt powder up to 30% and found that the compressive strength was increased by 24% and 26% at 28 days and 90 days, respectively. They concluded this increase was due to improved particle packing, denser cement matrix, and enhanced ITZ. Likewise, flexural strength increased by 28% and 24% on 28 days and 90 days, respectively. Similar results were also reported by Binici & Aksogan (2018), who incorporated up to 100% basalt powder as fine aggregate and observed an increase in compressive strength with the increase in basalt powder at all ages. The compressive strength was found to be 30%, 28%, and 23% higher than the control mix at 7, 28, and 90 days. In another study, Binici et al. (2020) studied the mechanical performance of concrete augmented with basalt powder as both SCM and fine aggregate. They obtained the highest compressive strength at 10% and 40% replacement of cement and sand, respectively. Li et al. (2021) introduced basalt powder obtained from tunnel waste as SCM in producing Ultra-High-Performance Concrete (UHPC) to reduce the cost and environmental impact and achieved an optimum replacement level of 15% with basalt powder. In another study, Sharaky et al. (2022) tested basalt as SCM as well as fine aggregate up to replacement levels of 20% and 80%, respectively. They observed no significant differences in compressive and tensile strengths up to 10% and 40% replacement of cement and sand, respectively as compared to the reference sample. In a recent study by BoÄa & Åenol (2023), 21 basalt was used as coarse aggregate for up to 100% replacement, which resulted in increased compressive and splitting tensile strengths. The compressive and splitting tensile strengths increased with the curing time and were highest at a 100% replacement ratio for all curing ages. The compressive strength with a 100% replacement ratio was found to be 19.2% and 19.5% more than the control specimen after 28 and 180 days, respectively. Li et al. (2018) investigated the application of basaltic coarse aggregate in addition to other SCMs such as MicroSilica, Limestone powder, and steel fibers to produce UHPC and noticed a slight reduction in compressive and flexural strengths. Celik et al. (2014) utilized basalt powder as an additive up to 50 % replacement in combination with another SCM i.e. Limestone with a fixed proportion of 15% in a ternary concrete mixture and observed that cement can be replaced with 30% basalt powder and 15% limestone to produce a low cost and environment-friendly concrete with strength comparable to conventional concrete. Overall, basalt powder has the potential to be utilized in the production of ultra-high-performance cementitious composites (de Matos et al., 2020). 2.2.1.2 Durability Properties Basalt powder can potentially enhance the post-fire mechanical performance of mortar mixes (Yurt et al., 2024). Geopolymer mortar mixes by combining basalt powder with glass powder in varying proportions were developed by Yurt et al. (2024). They investigated the mechanical performance in terms of compressive and flexural strengths before and after high-temperature exposure up to 800°C at 1, 28, and 90 days of air curing. They concluded that the residual compressive strength was highest in mortar mixes with 75% basalt and 25% glass powder at all ages. The residual flexural strength was highest in mortar mixes with 75% basalt and 25% glass powder at all ages up to 600°C. However, at 800°C, the residual flexural strength of mortar mixes was not consistent and varied over time. Sevinç & Durgun (2023) heated the samples of mortar mixes, prepared with 22 basalt powder, pumice, and barite as SCMs up to 15 % replacement, to 600°C at the rate of 5°C/min. They observed that basalt powder with a 7.5% replacement ratio resulted in the lowest mass loss of up to 2% at all temperatures and the highest residual compressive strength of up to 500°C among all considered additives. Similar results about the highest residual compressive and flexural strengths and lowest weight loss in mortars at 15% cement replacement with basalt powder and after exposure to 800°C were reported by Ãelikten & Baran (2024b). In a recent study, Wembe et al. (2024) incorporated Basalt as fine and coarse aggregates in concrete and observed a 36% residual compressive strength at 600°C. Uysal et al. (2012) conducted a comparative study using basalt, limestone, and marble powder as cement substitutes for up to 30% and 2% polypropylene fibers in self-compacting concrete. They exposed the concrete specimens up to 800°C at a heating rate of 1°C/min and found that the residual compressive strength was highest in basalt powder among all the considered concrete mixes. Also, the weight loss in basalt powder with and without polypropylene fibers specimens was lowest at a 20% replacement ratio. Water absorption represents the porous structure or capillary pores of the concrete, and the porosity or voids substantially influence the concrete behavior under chloride attack and F-T conditions (Binici & Aksogan, 2018). Using additives can significantly decrease the voids due to the filler mechanism and, consequently, could improve water penetration, chloride penetration, and the F-T resistances of concrete (Hossain & Lachemi, 2004) (Celik et al., 2014) (Binici & Aksogan, 2018). They investigated the durability properties of concrete, such as water absorption, chloride penetration resistance, and F-T resistance, incorporating various SCMs. Hossain & Lachemi (2004) observed an increase in chloride penetration resistance with increased volcanic ash content. Binici & Aksogan (2018) conducted a comparative study with different additives such as granite, marble, silica, and basalt to replace fine aggregate up to 100% in concrete. They concluded that 23 basalt powder samples had the lowest water absorption and the highest residual compressive strength after F-T exposure among all considered additives and reference samples. Another study by Binici et al. (2020) highlighted that concrete augmented with basalt powder can enhance durability properties such as F-T resistance and water absorption. They reported a reduction in mass and compressive strength of 2.1% and 11.8% up to 20% cement replacement, 5.5% and 7.2% up to 40% sand replacement, and 3% and 10% up to 20% each cement-sand replacement as compared to 13.9% and 15.3% losses, respectively, in the reference sample. The water absorption in basalt-augmented samples was also 23% lower than in the reference sample. Likewise, Celik et al. (2014) also analyzed that water absorption and chloride ingress were lower in concrete mixes with 30% basalt powder than in conventional concrete. However, Türk et al., (2022) stated that the water absorption of mortars with basalt powder in varying proportions (5-40%) was found to be (0.57-2.16%) higher than the control sample. BoÄa & Åenol (2023) also concluded that concrete with 100% basalt coarse aggregate exhibited very low chloride permeability and further decreased with the increase in the curing period. 2.2.1.3 Microstructural Properties The microstructural properties of cementitious materials incorporating basalt powder have been extensively studied to evaluate their effects on hydration, particle packing, and ITZ. Scanning Electron Microscopy (SEM) investigations provide valuable insights into these mechanisms. Laibao et al. (2013) carried out SEM analysis on cement pastes blended with 30% basalt powder to determine the hydration processes and microstructural changes. At 28 days, the hydration products were present in small amounts as ettringite needles due to a slow pozzolanic reaction. However, the basalt particles were coated with thick CSH gel resulting from the hydration of Ca(OH)2 at 180 days. They also noticed that the unreacted particles acted as a filler. These filler 24 particles fill the intergranular free space, decreasing the porosity in the ITZ due to improved particle packing, eventually leading to a denser cement matrix and higher strength (Dobiszewska & Barnes, 2020b). The formation of micro-cracks along the aggregate surface inducing a weak bond between the aggregate and hydrated cement paste was also observed by Dobiszewska et al. (2018); however, these cracks were not visible in basalt-modified mixes. They also reported a chemical interaction between the basalt powder surface and the CSH phase, causing further densification of ITZ. Similar conclusions were made by BoÄa & Åenol (2023) regarding the micro-cracks in the reference sample and enhanced binder-aggregate interface in concrete with 100% basalt coarse aggregate. 24 Table 2.1 List of previous studies involving basalt powder in cement paste, mortar and concrete mixes Literature Basalt Type Mix Type Replacement Type Replacement Levels (%) Optimum Replacement Level (%) Properties Studied Hossain & Lachemi (2004) Volcano/ Mountain Mortar SCM 20 & 40 40 Compressive Strength, Chloride Ion Penetration Laibao et al. (2013) Stone Crushing Plant Cement Paste SCM 5, 10, 15, 20, 25 & 30 - Compressive Strength, Flexural Strength, Scanning Electron Microscopy El-Didamony et al. (2015) - Cement Paste SCM 5, 10, 15 & 20 20 Compressive Strength Dobiszewska & BeycioÄlu (2017) Asphalt Batch Mix Plant Cement Paste & Mortar SCM 1, 2, 3, 6, 8 and 10 8 Compressive Strength, Flexural Strength Dobiszewska et al. (2019) Asphalt Batch Mix Plant Cement Paste & Mortar SCM 10, 20, 30 & 40 5, 10, 15 & 20 - Compressive Strength, Flexural Strength Dobiszewska & Barnes (2020) Asphalt Batch Mix Plant Mortar Sand Replacement 5, 10, 15 & 20 20 Compressive Strength, Flexural Strength 25 Literature Basalt Type Mix Type Replacement Type Replacement Levels (%) Optimum Replacement Level (%) Properties Studied de Matos et al. (2020) Quarry Waste Ultra High-Performance Cement Paste Mineral Additive - - Compressive Strength, Scanning Electron Microscopy Yu et al. (2020) Surface Quarries Mortar SCM 10, 20, 30, 40 & 50 - Compressive Strength, Flexural Strength Amin et al. (2020) Crushed Basalt Stone Mortar SCM 10, 20, 30 & 40 10 Compressive Strength, Water Absorption Liu et al. (2021) Basalt Stone Material Factory Cement Paste SCM 5, 10 & 20 5-10 Compressive Strength Türk et al. (2022) - Self Compacting Mortar SCM 5, 10, 15, 20, 25, 30, 35 & 40 10 Compressive Strength, Flexural Strength, Water Absorption Sevinç & Durgun (2023) Basalt Rock Mortar SCM 7.5 & 15 7.5 Compressive Strength, Elevated Temperature, Scanning Electron Microscopy 26 Literature Basalt Type Mix Type Replacement Type Replacement Levels (%) Optimum Replacement Level (%) Properties Studied Yurt et al. (2024) Stone Cutting Plant Geopolymer Mortar SCM 25, 50, 75 & 100 75 Compressive Strength, Flexural Strength, Elevated Temperature, Scanning Electron Microscopy Ãelikten & Baran (2024) Stone Cutting Workshop Mortar SCM 5, 10, 15, 20 & 25 15 Compressive Strength, Flexural Strength, Elevated Temperature Uysal (2012) Quarry Waste Self Compacting Concrete SCM 10, 20 & 30 20 Compressive Strength, Elevated Temperature Celik et al. (2014) Quarry Concrete SCM 30 & 50 30 Compressive Strength, Workability, Chloride Permeability, Water Absorption Binici & Aksogan (2018) Industry Waste Concrete Sand Replacement 10, 20, 30, 40, 50 & 100 100 Compressive Strength, Water Absorption, Freeze-Thaw Resistance 27 Literature Basalt Type Mix Type Replacement Type Replacement Levels (%) Optimum Replacement Level (%) Properties Studied Li et al. (2018) - Ultra High-Performance Concrete Coarse Aggregate 100 - Compressive Strength, Tensile Strength Dobiszewska et al. (2018) Asphalt Batch Mix Plant Concrete Sand Replacement 5, 10, 20 & 30 30 Compressive Strength, Flexural Strength, Scanning Electron Microscopy Binici et al. (2020) Pyroclastic Flow Concrete SCM and Sand Replacement 5, 10, 15 & 20 10, 20, 30 & 40 10 40 Compressive Strength, Water Absorption, Freeze-Thaw Resistance Li et al. (2021) Tunnel Waste Ultra High-Performance Concrete SCM 15, 30 & 45 15 Compressive Strength, Environmental Impact Boga & Senol (2023) Stone Quarry Concrete Coarse Aggregate 25, 50, 75 & 100 100 Compressive Strength, Splitting Tensile Strength, Rapid Chloride Permeability, Scanning Electron Microscopy 28 Literature Basalt Type Mix Type Replacement Type Replacement Levels (%) Optimum Replacement Level (%) Properties Studied Wembe et al. (2024) Quarry Concrete Sand Replacement & Coarse Aggregate 100 & 100 - Compressive Strength, Splitting Tensile Strength, Scanning Electron Microscopy, Elevated Temperature 29 2.3 Wood Ash Wood ash is an industrial waste generated by the combustion of wood for energy production in wood-fired boilers and power plants (Hussain et al., 2017). Typically, wood combustion produces 6-10% of wood ash, out of which 70% is dumped into landfills (Siddique, 2012). Due to its pozzolanic characteristics and low ecological health concerns, wood ash has the potential to be utilized as a cement substitute up to certain replacement levels (Rumman et al., 2023). However, the source of origin, such as wood type, combustion technique, and temperature, plays a vital role in defining the pozzolanic properties of wood ash (Hamid & Rafiq, 2020). Low-temperature wood ash from whole trees, including bark, logs, buds, and needles, possesses higher pozzolanic activity than high-temperature wood ash from wood pellets (Sigvardsen et al., 2019). Literature indicates that incorporating wood ash as a partial replacement of cement in mortar and concrete mixes enhances the mechanical and durability properties (Ramos et al., 2013). It also offers a carbon-neutral alternative since the carbon absorbed during the wood growth balances out combustion emissions (Lazik, Bošnjak, Ãetin, & Küçük, 2020). Therefore, the utilization of wood ash in construction activities provides a viable solution for sustainable construction by fostering effective waste management and lowering carbon footprint by mitigating construction industry emissions (FoÅt et al., 2020) as well as construction costs (Bostanci, 2019). 2.3.1 Effects of Using Wood Ash Previous research studies regarding wood ash have incorporated it as SCM or cement replacement, as fine aggregate or sand replacement, and as an additive or filler in mortar or concrete mixes, as shown in Table 2.2. The effects of using wood ash on the various 30 mechanical, durability and microstructural properties of mortar and concrete mixes are discussed below. 2.3.1.1 Mechanical Strengths (Compressive, Flexure, Tensile) The incorporation of wood ash in cementitious systems affects the compressive, flexural, and tensile strengths, with results varying based on replacement levels and curing time. Elinwa & Ejeh (2004) examined the compressive strength of mortar mixes with the introduction of sawdust ash as a cement replacement. They analyzed slow strength development and reduced strength at higher replacement levels compared to the specimen without ash. In pursuance, Elinwa et al. (2008) investigated the strength development in mortars after 90 days and detected a 30% increase in compressive strength at a 10% replacement level. Likewise, Garcia & Sousa-Coutinho (2013) also found that compressive strength decreases with the cement replacement and increases with the curing time. Studies indicate that there was no significant difference in flexural strength at all replacement values. Cheah & Ramli (2012) concluded similar findings regarding the rate of strength gain and flexural strength in mortars. They observed a 2.7% increase in compressive strength and a marginal difference in flexural strength at 15% cement replacement after 90 days. Rajamma et al. (2009) suggested an optimum replacement level of cement in mortars of up to 20%. Elinwa & Mahmood (2002) studied the influence of sawdust ash as a cement substitute on the compressive strength of concrete. They observed a strength reduction of 7%, 22%, and 32% with the increment of sawdust ash content from 5%, 10%, and 15% at 28 days. However, they noticed that the difference in strength as compared to the control sample decreases with the curing age due to the continuous hydration of cement and sawdust ash. Udoeyo & Dashibil (2002) also discovered lower compressive as well as flexural strengths at early ages and higher 31 at later ages. They obtained 4-25% and 1-4% lower compressive and flexural strengths, respectively, at 10-20% substitution levels compared to the reference sample after 28 days. In another study, Udoeyo et al. (2006) introduced wood ash as a mineral additive in concrete up to 30% by cement mass. They deduced that the mechanical performance in compression and flexure improves with age but declines with the increase of wood ash content. However, the strength enhancement at longer curing regimes was higher in mixes with lower wood ash content than higher wood ash content due to weak pozzolanic activity. The delayed strength enhancement was less pronounced in mixes with lower wood ash content due to increased surface area of wood ash. The growth in compressive strength after 90 days compared to 28 days was supplemented by 16.5%, 26%, 9% and 10% at 5%, 10%, 15% and 20% additive content. Similarly, Abdullahi (2006) also evaluated a decrease in compressive strength with the increase in wood ash content. Moreover, the strength reduction at 60 days was slightly decreased compared to 28 days in concrete. Chowdhury et al. (2014) also illustrated an identical trend in the experimental analysis of mechanical strengths, i.e., compressive, split tensile, and flexure with increased wood ash content and prolonged curing conditions. On the contrary, NagrockienÄ & DaugÄla (2018) achieved 1.2% and 4.2% higher compressive strengths up to 15% substitution of wood ash as SCM with reference to the control specimen at 7 and 28 days. Besides, FoÅt et al. (2020) also reported a 16% and 6% increment in compressive strength at 10% and 20% replacement of cement with wood ash. Furthermore, there was a significant increase of up to 33% and 19 %in flexural strength at replacement ratios of 10% and 20%. However, there was a considerable decrease in mechanical strength at higher substitution levels beyond 40%. In a recent study, Rumman et al. (2023) performed a comprehensive experimental investigation on the performance of both mortar and concrete 32 utilizing partially burnt wood ash as an SCM in 15%, 30%, and 45% substitution values. They observed the same pattern of strength development with the increased dosage of wood ash and curing time period in mortar and concrete mixes. However, the effect was more prominent in concrete specimens than in mortar specimens. The compressive strength loss in mortar and concrete specimens at 15% cement replacement after 28 days was 9.3% and 21.1%, respectively. Though the splitting tensile strength at 15% cement replacement was found to be commensurate with the reference specimen. This strength loss increased to 54.3% and 71.4% at 45% cement replacement in mortar and concrete specimens after 28 days. 2.3.1.2 Durability Properties Wood ash incorporation influences critical durability factors such as water absorption, F-T resistance, and chloride ion penetration. The results on water absorption vary. Elinwa & Ejeh (2004) reported a decreased water absorption in mortar mixes containing 15% sawdust ash due to the filling of air voids by ultrafine ash particles, leading to a denser microstructure. On the contrary, Cheah & Ramli (2012) stated that incorporating wood ash as a cement substitute in mortar mixes may result in higher water absorption. Similar findings were also demonstrated by Vu et al. (2019) in their study on wood-cement panels. Hussain et al. (2017) compared the water absorption in concretes prepared with wood ash and fly ash. They found that the water absorption increases with the increase of SCM content due to the hydrophilic property of ash. Still, wood ash showed significantly lower water absorption within the acceptable limits compared to fly ash. NagrockienÄ & DaugÄla (2018) observed a 4.12% decrease in water absorption up to 15% addition of wood ash. However, water absorption was increased with the further addition of wood ash. Concrete containing 5% and 30% wood ash contents presented the highest and lowest F-T resistance, respectively. 33 On the same note, Garcia & Sousa-Coutinho (2013) also concluded that the inclusion of wood ash as cement replacement increases the sorptivity and chloride permeability of mortars. Siddique et al. (2019) established a decrease in water absorption and chloride penetration at a 5% substitution level with sand compared to the control mix. At higher replacement ratios of up to 20%, the water absorption and chloride penetration of concrete increased with the increase in wood ash by up to 40%. Nevertheless, the water absorption was found to be decreased with the curing age. Rumman et al. (2023) attained improved chloride penetration resistance up to 19% at 15% wood ash content. However, it was reduced considerably at a wood ash content of 30% and above, resulting in less durable concrete. Rissanen et al. (2020) performed a comparative study on the F-T resistance of mortars with and without air entrainment. They considered untreated wood ash, milled wood ash and coal fly ash with varying percentages of air entraining agent (i.e., 0.005%, 0.015%, 0.05% and 0.2%). The cement was replaced by 20% in all the mixes. The F-T performance was improved in all the mortar mixes with air entrainment of 10-20%. At 10% air content, the F-T resistance of untreated wood ash mortar was enhanced by 20% in terms of compressive strength, whereas it was reduced by 40% in coal fly ash mortar. Jura & Ulewicz (2021) formulated a concrete mix incorporating wood ash as sand replacement in varying percentages and gravel and basalt as coarse aggregates. They determined that wood ash concrete prepared with basalt aggregates had lower water absorption and higher residual compressive strength values after F-T cycles than gravel aggregates at all replacement levels. The water absorption was assessed to be 0.35% higher than the reference mix, and the reduction in residual compressive strength after F-T exposure was found to be 1.8% in concrete with 30% wood ash and basalt aggregates. 34 To the best of my knowledge, no literature is available to date regarding the performance of concrete incorporating wood ash at elevated temperatures. 2.3.1.3 Microstructural Properties The microstructural characteristics of wood-ash modified cementitious materials provide insights into their impact on the ITZ, porosity, and hydration processes. Elinwa et al. (2008) examined the microstructural properties in self-compacting concrete with 10% sawdust ash as SCM and observed that 96% of Ca(OH)2 was hydrated at 90 days, leading to the formation of 84% of secondary CSH gel. Subsequently, this helped produce a dense and homogeneous microstructure by regulating the pore size distribution of ITZ. Vu et al. (2019) performed SEM on mortars with 30% wood ash and found a uniform and dense microstructure with low porosity and pore sizes smaller than 10µm. Hussain et al. (2017) also manifested a similar morphology with small pore sizes due to the densification of microstructure by adding wood ash as a nucleation site. The filler mechanism occurred with a further increase in ash content due to cement dilution. Siddique et al. (2019) also noticed the formation of ettringite needles in the SEM analysis of concrete utilizing wood ash as a sand substitute. The minimum voids in wood ash concrete were reported at a 5% replacement ratio. Rumman et al. (2023) noted decreased CSH gel formation and increased Calcium Hydroxide (CH) by adding partially burnt wood ash in mortar mixes, resulting in strength loss. 35 Table 2.2 List of previous studies incorporating wood ash in cement paste, mortar and concrete mixes Literature Wood Ash Type Combustion Temperature (°C) Mix Type Replacement Type Replacement Levels (%) Optimum Replacement Level (%) Properties Studied Elinwa & Ejeh (2004) Timber Milling Industry - Mortar SCM 5, 10, 15, 20, 25 & 30 10 Compressive Strength, Water Absorption Elinwa et al. (2008) Thermally Activated Timber Waste 400-600 Mortar SCM 5, 10, 15, 20 10 Compressive Strength, Workability Rajamma et al. (2009) Thermal Power Plant Waste 800 & 1000 Cement Paste and Mortar SCM 10, 20 & 30 20 Compressive Strength, Flexural Strength, Scanning Electron Microscopy Cheah & Ramli (2012) Wood Kiln Drying Factory Boiler Waste 800 Mortar SCM 5, 10, 15, 20 & 25 - Compressive Strength, Flexural Strength, Water Absorption 36 Literature Wood Ash Type Combustion Temperature (°C) Mix Type Replacement Type Replacement Levels (%) Optimum Replacement Level (%) Properties Studied Garcia & Sousa-Coutinho (2013) Forest Waste Bottom Ash - Mortar SCM 5 & 10 - Compressive Strength, Flexural Strength, Chloride Ion Penetration, Water Absorption, Scanning Electron Microscopy Ramos et al. (2013) Timber Processing Industry - Mortar SCM 10 & 20 20 Compressive Strength, Flexural Strength, Scanning Electron Microscopy Cheah et al. (2017) Rubber wood timber product manufacturing industry 800 Geopolymer Mortar SCM 10, 20, 30, 40, 50 , 60 . 70, 80, 90 &100 50 Compressive Strength, Flexural Strength 37 Literature Wood Ash Type Combustion Temperature (°C) Mix Type Replacement Type Replacement Levels (%) Optimum Replacement Level (%) Properties Studied Vu et al. (2019) Thermal Energy Production Plant - Wood-Cement Mix SCM 10, 20, 30, 40 & 50 30 Flexural Strength, Workability, Water Absorption, SEM Rissanen et al. (2020) Fluidized Bed Combustion of Peat and Wood 790 Mortar SCM 20 with different Air Content - Compressive Strength, Air Content, Freeze-Thaw Resistance Elinwa & Mahmood (2002) Timber Milling Industry - Concrete SCM 5, 10, 15, 20, 25 and 30 - Compressive Strength Udoeyo & Dashibil (2002) Sawdust Dumping Site - Concrete SCM 10, 15, 20, 25 & 30 10-20 Compressive Strength, Splitting Tensile Strength Udoeyo et al. (2006) Timber Market Dump Site (1000) 1000 Concrete Mineral Additive 5, 10, 15, 20, 25 & 30 5-10 Compressive Strength, Flexural Strength 38 Literature Wood Ash Type Combustion Temperature (°C) Mix Type Replacement Type Replacement Levels (%) Optimum Replacement Level (%) Properties Studied Abdullahi (2006) Bakery - Concrete SCM 10, 20, 30, & 40 20 Compressive Strength, Workability Ghorpade (2012) - - Concrete SCM 10, 20 & 30 10 Compressive Strength, Split Tensile Strength Chowdhury et al. (2015) Wood Polishing Unit (700) 700 Concrete SCM 5, 10, 15, 18 & 20 Compressive Strength, Flexural Strength Hussain et al. (2017) Pulp Mill Waste - Concrete SCM 10, 20, 30, 40, 50 & 60 20 Compressive Strength, Water Absorption Hussain et al. (2017) Pulp Mill Waste - Concrete SCM 10, 20, 30, 40, 50 & 60 20 Compressive Strength, Water Absorption, Scanning Electron Microscopy 39 Literature Wood Ash Type Combustion Temperature (°C) Mix Type Replacement Type Replacement Levels (%) Optimum Replacement Level (%) Properties Studied Nagrockiene & Dauge la (2018) - - Concrete SCM 5, 10, 15, 20, 25 & 30 15 Compressive Strength, Water Absorption, Freeze-Thaw Resistance Bostanci (2019) Domestic Heating Purposes Waste - Concrete SCM 5 & 12.5 5 Compressive Strength, Workability Siddique et al. (2019) Wood-fired Boiler Waste - Concrete Sand Replacement 5, 10, 15 & 20 5 Compressive Strength, Split Tensile Strength, Workability, Water Absorption, Rapid Chloride Ion Permeability, Scanning Electron Microscopy 40 Literature Wood Ash Type Combustion Temperature (°C) Mix Type Replacement Type Replacement Levels (%) Optimum Replacement Level (%) Properties Studied Fort et al. (2020) - - Concrete SCM 10, 20, 30, 40, 50, 60 & 70 30 Compressive Strength, Flexural Strength Jura & Ulewicz (2021) Fluidized Bed Combustion of Wood-Sunflower Biomass - Concrete Sand Replacement 10, 20, 30 and 40 10-30 Compressive Strength, Water Absorption, Freeze-Thaw Resistance Hamid & Rafiq (2021) Restaurant Stoves and Wood Processing Plants - Concrete SCM 10, 15, 20 & 25 10 Compressive Strength, Workability 41 Literature Wood Ash Type Combustion Temperature (°C) Mix Type Replacement Type Replacement Levels (%) Optimum Replacement Level (%) Properties Studied Rumman et al. (2023) Timber Industry 615-650 Mortar & Concrete SCM 15, 30 & 45 15, 30 & 45 15 Compressive Strength, Split Tensile Strength, Rapid Chloride Permeability Test, Scanning Electron Microscopy 42 2.4 Effects of Mixing Water Temperature The temperature of mixing water plays a critical role in influencing the workability, hydration process, and strength development of the cement mixes. Elevated water temperatures can accelerate hydration in the early stages but may adversely affect long-term strength and microstructural uniformity (Eskandarsefat, 2018). Concrete using hot mixing water with temperatures varying from 25-100°C was prepared by Naganathan & Mustapha (2015). They noticed an improvement in the early strength of concrete with the increase in temperature due to the accelerated rate of hydration. However, the strength after 28 days was decreased due to the retarded subsequent hydration and uneven distribution of hydrates within the matrix. The accelerated initial rate of hydration reduced the time to diffuse for hydrates away from cement particles and thereby increased the concentration of hydrates near the cement particles resulting in retarded subsequent hydration and decreased strength at later ages. Nasir et al. (2016) studied the influence of the casting temperature of concrete with different SCMs on compressive strength at 3,7,28, 90 and 180 days. They found that the mechanical properties, i.e., compressive and split tensile strengths of concrete with and without SCMs, increased with the temperature increase until 7 days due to intensified pozzolanic reactivity. However, the mechanical strengths of concrete with and without SCM increased up to 38°C and 32°C, respectively, after 28 days. Further increase in temperature causes a reduction in the strengths of both types of concrete after 28 days. Madi et al. (2017) examined the concrete mixes with four different water-binder ratios varying from 0.35 to 0.50 at 5, 15, 30, and 45°C. The compressive strength was found to be increased at all water-binder ratios with the curing age and mixing water temperature. However, the highest compressive strength at later ages i.e., 7 to 28 days, was detected in concrete with 0.35 water-binder ratio at all mixing water 43 temperatures. Assal & Abou-Zeid (2019) stated that the highest compressive and flexural strengths at 28 days were yielded at a mixing water temperature of 5°C. Tan & Nichols (2004) recommended incorporating SCMs into cement mixes to counteract the adverse effects of elevated water temperatures. SCMs moderate the hydration process, promoting uniformity and reducing the risk of long-term strength loss. 2.5 Summary This chapter highlighted the behavior of conventional concrete under harsh weather conditions such as F-T action, chloride attack and elevated temperature exposure. A comprehensive review of the available literature incorporating basalt powder and wood ash was also illustrated. The review provided insight into the effects of using basalt powder and wood ash on mechanical properties such as compressive, flexure and tensile strengths; durability properties such as F-T, chloride attack and elevated temperature; and microstructural properties of the mortar and concrete mixes in the light of previous studies. The influence of basalt powder and wood ash as an SCM, cement or sand substitute in different mix proportions on the aforementioned properties of mortar and concrete mixes reported in the past research was also discussed. The optimum replacement percentage of both basalt powder and wood ash was identified based on the literature. Besides, the effects of mixing water temperature on the pozzolanic activity of cementitious composites were also elaborated. 44 Chapter 3: Mix Design and Experimental Testing 3.1 General This chapter discusses the mix design proportions of mortar and concrete mixes in addition to the physical properties of materials used. It also explains the various test methods adopted and their setups utilized to determine the mechanical and durability characteristics of mortar and concrete mixes. ASTM standard was used to prepare the mix design of mortar. However, the mix design of concrete was done in reference to CSA standards. Only ASTM standards were followed when performing the various tests on both mortar and concrete mixes. The replacement levels of different ingredients of mortar were considered based on the available literature. However, the substitution levels of different constituents of concrete were taken into account depending on the results obtained from mortar mixes after validation from past studies on concrete. 3.2 Materials Mortar mixes were prepared with Type 1 general-use limestone (GUL) cement or Portland limestone cement, partially burnt wood ash, and basalt powder. Concrete mixes were produced using general-use limestone (GUL) cement, partially burnt wood ash, natural fine sand, basalt powder and 3/8â (or 9.5 mm) crushed stone aggregate. MasterAir AE 90, conforming to ASTM C260/C260M-10a (2024), was used as an air entraining admixture (AEA) in all the mortar and concrete mixes, as shown in Figure 3.1(a). Sika Viscocrete 2100 and Sika Viscocrete 6100, conforming to ASTM C494/C494M (2024), were utilized as high-range water-reducing admixtures (HRWRA) in all the mortar and concrete mixes, respectively, as illustrated in Figure 3.1(b). Portland limestone cement conforming to ASTM C595/C595M (2024) was used 45 as a binding agent in all the mixes provided by the Kamloops, BC based facility of Lafarge. Tolko Industries, located in Armstrong, BC, supplied the partially burnt wood ash, as shown in Figure 3.2(b), from one of the timber manufacturing plants. Basalt powder, as shown in Figure 3.2(a). was obtained from the mining company CanLava, situated in Langley, BC. Coarse (or crushed stone) aggregate and fine sand were procured from Kelowna Ready Mix. a) Basalt powder b) Wood ash Figure 3.1 Constituents of concrete a) Air entraining admixture b) High range water reducer Figure 3.2 Admixtures used in the concrete 46 The material properties of crushed stone aggregate, fine sand, and basalt powder were determined following the ASTM C127 (2024) and ASTM C128 (2022) standards, respectively. Table 3.1 illustrates the properties of materials used in mortar and concrete mixes. Table 3.1 Material properties of aggregates Aggregates Bulk Density (kg/m3) Specific Gravity Absorption (%) Relative Density (Oven Dry) Relative Density (Saturated Surface Dry) Apparent Relative Density Crushed Stone Aggregate 1600 2.59 2.63 2.71 1.76 Fine Sand - 2.56 2.64 2.8 3.37 Basalt Powder - 2.34 2.5 2.79 7 3.2.1 Characterization of Wood Ash The wood ash used in this study was sourced from the same batch utilized in previous research by a lab colleague. Consequently, its material characterization properties were adopted from the findings reported by Rumman et al. (2023). According to their study, the wood ash exhibited a darker color compared to cement and consisted of a blend of spherical and irregularly shaped particles. Since the wood ash was partially burnt, high-carbon and porous biochar particles were also observed. The physical properties of wood ash included a natural moisture content of 3.07%, a specific gravity of 2.75%, and a specific surface area of 1205 cm2/g. The chemical composition of wood ash was analyzed using X-ray fluorescence (XRF), as presented in Table 3.2. The wood 47 ash was also found analogous to the Class C coal fly ash. It can be inferred from Table 3.2 that the sum of SiO2, Al2O3 and Fe2O3, i.e., 59.87%, was higher than the specified limits of ASTM C618, i.e., 50%, to qualify as a pozzolanic material. Additionally, thermogravimetric analysis (TGA) revealed a thermal degradation of 10.25% when heated at a rate of 10°C/min up to 900°C. These characteristics indicate that wood ash possesses potential as a sustainable SCM in concrete applications. Table 3.2 Chemical composition of wood ash (Rumman et al., 2023) Chemical Composition (%) SiO2 41.71 Al2O3 10.06 Fe2O3 8.10 CaO 27.23 TiO2 0.88 SO3 0.04 K2O 6.53 MgO 2.37 MnO 0.82 3.2.2 Characterization of Basalt Powder The characterization of basalt powder was conducted using XRF and X-ray Diffraction (XRD) analyses to determine its chemical and mineralogical properties. The chemical composition was obtained using a Malvern Panalytical Epsilon 1 XRF analyzer and is shown in Table 3.3. 48 The analysis revealed that basalt powder contains significant amounts of SiO2, Al2O3 and Fe2O3. However, their combined concentration of 43.85% falls below the ASTM C618 (2023) threshold of 70% required for classification as a natural pozzolan. The XRD was carried out to analyze the phase properties and crystallinity of Basalt powder. The qualitative phase analysis of Basalt powder was carried out using Bruker D8 Advanced with DaVinci Powder X-Ray Diffractometer equipped with a Ni Kβ filter, 0.681mm incident slit, and an Eiger 2R 500K detector. Cu/Kα X-rays were generated over a 2θ range of 5° to 90° with step size and step time of 0.006° and 4 sec, respectively. . The sample elevation was defined manually with the help of twin laser system attached to the diffractometer. The samples were swung arbitrarily in the X/Y plane to enhance the particle statistics. Figure 3.3 shows the XRD pattern of basalt powder. It can be observed from the XRD diffractogram of basalt powder shown in Figure 3.3 that Plagioclase, along with Amphibole and Pyroxenes, were present in higher proportions. Besides, Illite and Haematite were also present in small amounts. Plagioclase is a tectosilicate mineral; Amphibole is an inosilicate and Pyroxenes are ferromagnesium silicate. The presence of these silicate crystals in higher proportions supports the results of XRF. Illite is an Alumino-silicate mineral, and Haematite is an iron oxide. 49 Table 3.3 Chemical composition of basalt powder Chemical Composition (%) SiO2 23.56 Al2O3 7.78 Fe2O3 12.51 CaO 7.29 TiO2 3.04 SO3 0.07 K2O 1.64 Cl 0.03 MnO 0.13 Figure 3.3 XRD pattern of basalt powder 50 TGA was also conducted on Basalt powder to evaluate its thermal stability. Waters Discovery TGA 550 thermogravimetric analyzer was used to perform the TGA on a sample mass of 40 mg approximately at a heating ramp of 10 °C within a 25 to 900 °C temperature range under a Nitrogen atmosphere. Figure 3.4 shows the TGA curve of Basalt powder, and it can be inferred that basalt powder is a thermally stable material with a total weight loss of 0.65% (Matykiewicz et al., 2019). The initial weight loss of 0.2% up to 400 °C may be due to the loss of adsorbed water (Iorio et al., 2018). The sharp degradation of 0.45% at 400°C may occurred due to the loss of impurities present in basalt powder. Figure 3.4 TGA curve of basalt powder 3.2.3 Gradation of Aggregates To determine the particle size distribution, sieve analysis was conducted on all the aggregates, including crushed stone aggregate, fine sand, and basalt powder, in accordance with the ASTM 51 C136 (2014). The particle size distribution curves thus obtained are shown in Figure 3.5. The coarser and finer limits considered in the curves were obtained from ASTM C33/C33M â 18 (2018) to determine the gradation of aggregates. It was observed that the crushed stone aggregate and fine sand were well-graded and within the ASTM C33/C33M â 18 (2018) coarser and finer limits. Basalt powder was also found to be well-graded however, it was a bit finer than the ASTM standard limits due to the presence of microfines. The fineness modulus of fine sand and basalt powder was 3.68 and 1.4. The nominal maximum size was evaluated as 14mm, 5mm, and 1.25mm for crushed stone aggregate, fine sand, and basalt powder, respectively. (a) Coarse Aggregate (b) Fine Aggregate Figure 3.5 Gradation of aggregates 3.3 Mix Design of Mortar All the mortar mixes were prepared in compliance with the ASTM C109/C109M (2024). A total of 38 mortar mixes, in addition to the control mix, were prepared to evaluate the effect of basalt powder and partially burnt wood ash on the mortar strength. The 38 mortar mixes include control mixes with and without AEA, 22 mixes prepared using tap mixing water and 14 mixes prepared using hot mixing water. A total of 9 specimens were prepared for each mortar mix to 52 examine their strength at 7, 28, and 56 days. Three different cases were considered for this study, replacing each mortar constituent at various replacement levels. Firstly, basalt powder was utilized as a sand substitute in the mortar, followed by the cement replacement, as shown in Table 3.4 and Table 3.5, respectively. In the mix designation BS05, BS represents basalt as sand substitute, and 05 represents the substitution percentage. Similarly, in the sample code BC05, BC indicates the incorporation of basalt replacing the cement, and 05 indicates the replacement percentage. Finally, partially burnt wood ash was incorporated as a cement replacement, and basalt powder was used as a sand substitute, as shown in Table 3.6. The sample code BAC was used to illustrate the mixes with basalt powder as sand substitute and wood ash as cement replacement, whereas 05 shows the replacement percentage of cement with wood ash. Additionally, mortar mixes with two different mixing water temperatures, i.e., 50°C and 90°C, were also prepared and compared with the mortars prepared using tap water, as shown in Table 3.7, to observe the influence of mixing water temperature on the early strength of mortar. The sample code HBAC was used to indicate the mortars prepared with hot mixing water followed by the replacement percentage of cement with wood ash, such as HBAC05. The control mix was prepared with 1 part of cement to 2.75 parts of sand by mass (i.e., cement: sand = 1:2.75). The water-to-binder ratio was taken as 0.485 by mass for all the mortar mixes. 53 Table 3.4 Basalt as sand replacement Sample Code Basalt Powder (%) Fine Sand (%) BS05 5 95 BS10 10 90 BS20 20 80 BS40 40 60 BS50 50 50 BS100 100 0 Table 3.5 Basalt as cement replacement Sample Code Basalt Powder (%) Cement (%) BC05 5 95 BC10 10 90 BC15 15 85 BC20 20 80 BC25 25 75 BC30 30 70 BC35 35 65 BC40 40 60 BC45 45 55 BC50 50 50 54 Table 3.6 Wood ash as cement replacement and basalt powder as fine sand replacement Sample Code Wood Ash (%) Cement (%) Basalt Powder (%) Fine Sand (%) BAC05 5 95 100 0 BAC10 10 90 100 0 BAC15 15 85 100 0 BAC20 20 80 100 0 BAC25 25 75 100 0 BAC30 30 70 100 0 Table 3.7 Mortar mixes prepared using hot mixing water Sample Code Wood Ash (%) Cement (%) Basalt Powder (%) Fine Sand (%) Control 0 100 0 100 HBAC05 5 95 100 0 HBAC10 10 90 100 0 HBAC15 15 85 100 0 HBAC20 20 80 100 0 HBAC25 25 75 100 0 HBAC30 30 70 100 0 3.4 Mix Design of Concrete The concrete mix design was formulated per the (CSA A23.1:22) standard. A total of seven concrete mixes, including the control mix, were prepared in the lab following ASTM C192/C192M (2019) specifications, as shown in Table 3.8. Basalt powder was utilized as a sand substitute at three replacement levels by mass, i.e., 0%, 50%, and 100%. Cement was also replaced with partially burnt wood ash in different proportions by mass, i.e., 0%, 10%, and 20%. The concrete was designed for exposure class C-2, i.e., for non-structural purposes such as garage floors, steps, pavements, sidewalks, etc. The target design strength of concrete at 28 55 days was 30 MPa, and the water-to-binder ratio was 0.45 for all the concrete mixes. The amount of water was adjusted for each mix after the moisture content correction due to aggregate. Table 3.8 Mix proportions of concrete Mix Sample Code Cement Crushed Stone Fine Sand Water Basalt Powder Wood Ash (kg/m3) (kg/m3) (kg/m3) (kg/m3) (kg/m3) (kg/m3) M0 A00B00 395.0 768.0 842.8 173.1 0.0 0.0 M1 A00B50 395.0 768.0 421.4 185.4 386.8 0.0 M2 A10B50 355.5 768.0 412.1 185.6 378.3 39.5 M3 A20B50 316.0 768.0 404.7 185.7 371.5 79.0 M4 A00B100 395.0 768.0 0.0 197.8 773.7 0.0 M5 A10B100 355.5 768.0 0.0 197.7 756.5 39.5 M6 A20B100 316.0 768.0 0.0 197.5 743.1 79.0 3.5 Sample Preparation The preparation of mortar and concrete samples is explained in the following sub-sections. 3.5.1 Mortar Specimens The mortar specimens were prepared using cube molds with dimensions of 50 mm (2 inches) in accordance with ASTM C109/C109M (2024), as shown in Figure 3.6. To facilitate demolding and ensure uniform specimen shape, the interior surfaces of the molds were lightly coated with oil before casting. Due to limitations in the available mixer capacity, specimen preparation was conducted in two batches, i.e., batch 1 yielded six cubes, while batch 2 produced three cubes. All the materials required for each batch were precisely measured and mechanically mixed in accordance with ASTM C305 (2020). Initially, the pre-measured quantity of water was added to the mixing 56 bowl, followed by the addition of AEA and HRWRA. Cement was then incorporated into the water and allowed to hydrate for 30 seconds before mixing commenced. The mixing procedure involved a sequential approach: an initial slow-speed mixing at the rate of (140±5 r/min) for 30 seconds, followed by a gradual addition of sand over the next 30 seconds while maintaining slow mixing. After 60 seconds, the mixer was paused, and its speed was increased to medium (285±10 r/min) for an additional 30 seconds. Medium mixing was done for 30 seconds, and then the mixer was stopped for 90 seconds to scrape down the material adhering to the interior sides of the bowl with the help of a trowel. Finally, the mortar was mixed at medium speed for 60 seconds. Once prepared, the mortar was placed into the molds in two layers, each 25 mm thick, with 32 strokes of 10 mm diameter tamping rod applied to ensure proper compaction. The specimens were then stored in a curing room with controlled humidity (85%±5) for 24 hours. After initial curing, the specimens were demolded and returned to the curing room until testing. Figure 3.6 Casting of mortar specimens 3.5.2 Concrete Specimens The concrete specimens were prepared following the guidelines of ASTM C192/C192M (2019). A total of 196 concrete specimens were cast, consisting of 154 cylinders and 42 beams. 57 The sizes of cylinder and beam specimens, as recommended by ASTM standards for different tests of concrete, are presented in Table 3.9. The specimens were tested on different maturity days following the recommendations of ASTM standards. The compressive strength was measured at four different ages to determine the influence of SCM on strength development. Moreover, the RCPT, F-T, and sorptivity tests were performed after 56 days, considering the slower rate of hydration of wood ash. Table 3.9 Experimental program for concrete specimens Name of Test Sample Age (days) No. of Samples Dimensions (mm) Sample Molds Total Quantity (m3) ASTM Standard Compressive Strength 7, 28, 56, 90 12 100x200 Cylinder 0.019 C39 Flexural Strength 28 3 150x150x500 Beam 0.034 C78 Splitting Tensile Strength 28 3 100x200 Cylinder 0.005 C496 Rapid Chloride Ion Penetration Test (RCPT) 56 2 100x200 Cylinder 0.005 C1202 Freeze-Thaw Test 56 3 76x102x406 Beam 0.003 C666 Sorptivity Test 56 2 100x200 Cylinder 0.005 C1585 Elevated Temperature Exposure 28 3 100x200 Cylinder 0.005 E119 58 Due to mixer capacity limitations, casting was carried out in three batches. The number of specimens prepared in each batch is listed in Table 3.10. The quantities of each material were measured a day before casting, labeled, and stored in a controlled environment before mixing. The concrete mixer was moistened to avoid any loss of moisture during mixing. After draining out the excess water, crushed stone aggregates were added first, followed by fine sand, basalt powder, and cement. Then, the mixer started to mix the coarse aggregate and fine aggregate. The cement was added to the drum while keeping the concrete mixer running. Partially burnt wood ash was added into the mixer drum before the introduction of cement, when applicable. Finally, the water with AEA and HRWRA was then incorporated. The concrete mixer was operated for 3 minutes with all the ingredients, followed by a rest period of three minutes and, eventually, two minutes of final mixing. The drum of the concrete mixer was also checked for any deposits on the sides during the pause period. The concrete mixes with a high volume of wood ash were not mixed thoroughly, and lumps were visible after the final mixing. In this case, the concrete mix was continued for more time until the lumps disappeared, resulting in a proper mixture. Freshly mixed concrete was transferred into the wheelbarrow, to determine slump value and air content, which was carried out in accordance with ASTM C143/C143M (2020) and ASTM C231 (2024), respectively. The freshly mixed concrete was then poured into the oiled molds in layers and compacted with a tamping rod to achieve proper compaction. The cylindrical specimens were poured into three layers with 25 strokes, each layer of a 10 mm round tamping rod. Similarly, the beam specimens were poured into two layers with 54 and 30 strokes of a 16 mm round tamping rod for flexural strength and F-T tests. The molded specimens were then transferred to the curing room with a relative humidity of 85%±5 and demolded after 24 hours before final curing. 59 Table 3.10 Specimens prepared in each batch Batch Test Specimen 1 Compressive Strength + Water Absorption + RCPT + 3 Spares 19 Cylinders 2 Flexural Strength 3 Beams 3 Freeze-Thaw + Splitting Tensile Strength + Elevated Temperature Exposure 3 Beams + 6 cylinders 3.6 Experimental Testing The experimental testing program of mortar and concrete is categorized into three primary sections: (i) fresh properties, including flow and slump values; (ii) mechanical or hardened properties, encompassing compressive, flexural, and splitting tensile strengths; and (iii) microstructural properties. Additionally, the durability characteristics of concrete were thoroughly evaluated. 3.6.1 Mortar 3.6.1.1 Flow Value Test The flow value test was conducted on 12 mortar specimens, as detailed in Table 3.11, to assess the consistency of the mortar mixes. The selection of mortar mixes for the flow value test was based on their performance under compression. The test followed the standard procedures outlined in ASTM C230 (2023), with the exception that the flow table diameter used in this study was 243 mm instead of the standard 255 mm. Figure 3.7 shows the flow value test apparatus used in the experiment. The mold was placed on the top surface of the flow table after cleaning and drying. The mold was filled in two layers of 25 mm thickness, with each layer compacted using 20 strokes of a 10 mm diameter tamping rod. After finishing the top surface, the mortar was allowed to sit for one minute before the mold was carefully removed. The flow table was then dropped 25 times 60 within 15 seconds using a camshaft mechanism. Finally, the diameter of the spread of the mortar mix was measured along the scribed lines on the top of the flow table in four directions using vernier calipers. The consistency, or flow value, of each mortar mix was determined as the average spread relative to the initial base diameter. Table 3.11 Mortar mixes for flow value test Control BS50 BC10 BAC10 HBAC10@50 HBAC10@90 - BS100 BC20 BAC20 HBAC20@50 HBAC20@90 - - BC30 - - - Figure 3.7 Flow value test apparatus 3.6.1.2 Mechanical Properties 3.6.1.2.1 Compressive Strength The compressive strength of all mortar cubes was investigated following the guidelines of ASTM C109/C109M (2024). The specimens were cast in molds with dimensions 50mm x 50mm x 50mm. The dimensions of the cubes were measured and verified before testing with the help of vernier calipers. Three cubes from each mix were tested at curing ages 7, 28, and 56 days. 61 All the specimens were tested using a 200 kN Instron compression testing machine, shown in Figure 3.8, at a loading rate of 900 to 1800 N/s. The maximum load at failure was recorded, and the compressive strength of mortar cubes was calculated by dividing the load by the cross-sectional area subjected to compression. The reported compressive strength for each mortar mix was taken as the average of three tested specimens for a given curing age. Figure 3.8 Test setup for compressive strength of mortar 3.6.1.2.2 Flexural Strength Flexural strength testing was conducted on 12 selected mortar mixes at 28 days in accordance with the ASTM C348 (2021). The selection of mortar mixes for flexural testing was based on their performance under compression, as shown in Table 3.11. A flow value test was performed on all the mortar mixes before casting the prism specimens to ensure consistency. The prism specimens were cast in molds with dimensions 40mm x 40mm x 160mm. Two beams were prepared for each mortar mix, resulting in a total of 20 mortar beams. All the beams were cast in two layers and compacted using a wooden tamper with a tamping face of 62 22 mm x 85 mm, applying 12 strokes per layer. The beams were demolded after 24 hours and placed into the curing room until testing. Flexural strength was evaluated using a center-point loading method with a 200 kN Instron compression testing machine modified for flexural strength testing, as shown in Figure 3.9. The load was applied at the rate of 2500 to 2800 N/s. The flexural strength of prism specimens was calculated with the help of the following equation: Sf = 0.0028P Equation 3.1 where Sf = Flexural Strength in MPa and P = Peak load in N. Figure 3.9 Test setup for flexural strength of mortar 3.6.1.3 Microstructural Properties SEM and energy dispersive spectroscopy (EDS) were performed to examine the microstructural properties of mortar specimens. SEM images were taken with the Tescan Mira 3 XMU Scanning Electron Microscope, and EDS analysis was carried out using the Oxford Instruments X-Max EDS detector to identify the elemental composition of mortar specimens, 63 as shown in Figure 3.10. The broken chips of flexural strength test prisms were coated with a 10 nm-platinum-palladium coating before conducting SEM and EDS analyses. Figure 3.10 SEM and EDS test setup 3.6.2 Concrete 3.6.2.1 Fresh Properties The properties of freshly mixed concrete were assessed in terms of slump value and air content. The target slump value and air content of concrete mixes were taken as 75±20mm and 6 to 9%, respectively, in accordance with the (CSA A23.1-22) standard. The slump test was conducted following ASTM C143/C143M (2020) specifications, using a frustum-shaped mold with top and bottom diameters of 100 mm and 200 mm and a height of 300 mm. The mold was filled in three layers, and each layer was compacted with 25 strokes of a 16mm diameter tamping rod. After the top surface was finished by rolling the taming rod and removing the concrete from the surrounding base, the mold was lifted vertically upwards in 5 seconds. The vertical distance between the top of the mold and the displaced original center of the top surface of the specimen was recorded immediately with the help of a steel ruler and then reported as the 64 slump value. The air content of concrete mixes was determined by the pressure method using an air meter as per ASTM C231 (2024). The measuring bowl of the air meter was filled with freshly mixed concrete in three layers, with each layer rodded 25 times with a 16 mm diameter tamping rod. A wooden mallet was also used to tap the sides of the measuring bowl to remove any voids left by the tamping rod. The top layer was finished with the help of a strike-off bar, and the edge of the measuring bowl was cleaned thoroughly with the help of a rug. Afterward, the measuring bowl was sealed properly with the help of cover assembly and clamps. Water was then poured into the measuring bowl through one of the petcocks until it drained out from the other petcock to remove any air bubbles of voids. Air was pumped into the measuring bowl after closing both the petcocks. The percentage of air was then recorded from the pressure gauge and expressed as the air content of that concrete mix. 3.6.2.2 Hardened Properties 3.6.2.2.1 Compressive Strength The compressive strength of cylindrical concrete specimens was determined using a 3MN Instron compression testing machine, as shown in Figure 3.11, at a loading rate of 0.25 MPa/s ± 0.05 MPa/s, according to the specifications of ASTM C39/C39M (2023). The diameter and length of cylindrical specimens were recorded with the help of vernier calipers. All the specimens were capped during testing to ensure uniform load distribution. The specimens were subjected to the compressive load until failure with a well-defined fracture pattern. The maximum or peak load at the failure was noted, and compressive strength was calculated by dividing it with the cross-sectional area. The average strength of three cylindrical specimens was taken as the compressive strength of a concrete mix at a certain age. The calculated 65 compressive strength was checked with the variance limits, i.e. 10.6% for three cylinders and 9% for two cylinders, as per ASTM C39. a) Cylindrical concrete specimens b) Test setup Figure 3.11 Compressive strength of concrete 3.6.2.2.2 Flexural Strength The flexural strength or modulus of rupture of concrete was studied with the help of beams, which had dimensions of 150mm width, 150 mm height, and 500 mm length. Three beam specimens were prepared from the same batch of concrete, i.e., batch 2 for each mix, resulting in a total of 21 beams. All the beams were tested by a three-point loading method at 28 days following the guidelines of ASTM C78/C78M (2022). To center the beam over the loading block and support block accurately during loading, each specimen was marked at 75mm and 225mm from the center of the beam on both sides. The nominal span length of the beams was 450mm, and the specimens were turned on its side to get a smooth surface. All the specimens were tested until rupture at a loading rate of 0.9 MPa/min to 1.2 MPa/min, as shown in Figure 3.12. At the breaking point, the peak load was noted, and measurements were taken to check if the fracture line was falling within the middle third of the beam. The modulus of rupture of each specimen was calculated using the following formula: 66 ð¹ = ð·ð³ðð ð Equation 3.2 where, R = Modulus of rupture (MPa) P = Maximum load applied (N) L = Nominal span length (mm) b = average width of specimen (mm) d = average depth of specimen (mm) a) Beam specimens b) Test setup Figure 3.12 Flexural strength of concrete 3.6.2.2.3 Splitting Tensile Strength The splitting tensile strength of concrete was evaluated using cylindrical specimens of diameter 100mm and height 200mm at 28 days as per ASTM C496/C496M (2017) specifications. The top and bottom diameters of each specimen were calculated by taking the average of three readings. Similarly, length was obtained by averaging two lengths of each specimen. Two diametral lines were marked on each specimen in the same axial plane with the help of a try square fitted with a level. Two wooden bearing strips of a width of 25mm were used to ensure (a) Beam Specimens (b) Test Setup (a) Beam Specimens (b) Test Setup 67 uniform load application throughout the length of the cylindrical specimens. The specimens were centered along the marked diametral lines in alignment with the lower and upper bearing blocks and wooden bearing strips, as shown in Figure 3.13. The loading rate was kept between 0.7 MPa/min to 1.4 MPa/min until failure occurred. The peak load at failure and the failure pattern were recorded. The splitting tensile strength of concrete was calculated using the formula mentioned in Equation 3.3 and was checked for strength variations of different specimens from the same mix. ð» = ðð·ð ðð Equation 3.3 Where, T = Splitting tensile strength of concrete (MPa) P = Peak load at failure (N) l = average length of the cylindrical specimen (mm) d = average diameter of the cylindrical specimen (mm) Figure 3.13 Test setup for splitting tensile strength of concrete 68 3.6.2.3 Durability Properties Durability refers to the ability of concrete to withstand environmental conditions such as F-T cycles, chemical exposure and high temperatures without significant deterioration. In this study, the durability of concrete modified with wood ash and basalt powder was assessed through tests on F-T resistance, RCPT, sorptivity and elevated temperature exposure. 3.6.2.3.1 Freeze-Thaw The F-T resistance of concrete was studied using rapid freezing and thawing in water method on concrete beam specimens with the help of a Humboldt H3185 S F-T cabinet, as shown in Figure 3.14. Three beam specimens of width 102mm, height 76mm, and length 406mm were prepared for each concrete mix, resulting in a total of 21 beams. The beam specimens were placed in the curing room after demolding at a relative humidity of 85 ± 5% for 21 days, and then the beams were cured in lime water for 7 days before testing. Two beam specimens of each mix were placed in the F-T cabinet at 28 days and subjected to 150 repeated cycles of freezing and heating. The beam specimens were taken out of the chamber to measure the change in weight and deterioration after every 30 cycles. To ensure uniform exposure to F-T, all beam specimens were flipped upside down every 30 cycles. The temperature range was kept between 4 ± 2 °C to -18 ± 2 °C as shown in Figure 3.15. One beam specimen of each mix was kept in the curing room throughout the testing period, and it was not exposed to any F-T cycle. After the completion of 150 F-T cycles, the beams were tested for residual flexural strength and compared with the beam without F-T exposure. Finally, F-T resistance was evaluated in terms of residual flexural strength, mass loss, and deterioration of beams. 69 Figure 3.14 Freeze-thaw cabinet Figure 3.15 Freeze-thaw cycle 3.6.2.3.2 Rapid Chloride Ion Penetration Test The RCPT was conducted on concrete specimens at 56 days in accordance with ASTM C1202 (2022). Two cylindrical specimens from each mix were cut into slices having 50mm ± 3 thickness and 100mm diameter. The sliced specimens were coated with epoxy on the sides to prevent any moisture loss during the test. Then, the specimens were placed into the desiccator fitted with a vacuum pump at an absolute pressure of 50mm Hg for 3 hours. Afterward, the de-aerated water was poured into the desiccator until the specimens were completely submerged 70 into the water by 3mm with the help of a separatory funnel without allowing any air and left for one additional hour. The specimens were then left soaked under water for 18 hours ±2 hours. Two solutions, namely 3% Sodium Chloride (NaCl) solution and 0.3 N Sodium Hydroxide (NaOH), were prepared in distilled water to measure the electrical conductance of the prepared specimens. Finally, the specimens were tested using 8 channels. The PROOVEâit apparatus was equipped with two cells designed for the RCPT test, as shown in Figure 3.16. One of the cells was filled with NaCl solution, and the other cell was filled with NaOH solution, and both the cells were connected to the negative and positive terminals, respectively. The specimens were subjected to a potential difference of 60V dc for 6 hours, the charge passed in coulombs, and the temperature was recorded every 30 minutes. The total charge passed over the test period was calculated using the formula below. The resistance of concrete specimens to the chloride ion penetration was reported in terms of the charge in coulombs passed through the sliced concrete specimens in 6 hours. Q = 900 (I0 +2I30 + 2I60 +â¦. + 2I300 + 2I330 + 2I360 ) Equation 3.4 where, Q = charge passed in coulombs I0 = current in amperes immediately after the voltage is applied It = current in amperes at time (t) after the voltage is applied The total charge passed through sliced concrete specimens was adjusted for the actual size of specimens using the following formula: QS = QXY x (95/X)2 x (Y/50) Equation 3.5 where, QS = charge passed in coulombs through a standard specimen of 95 mm diameter and 50 mm thickness QXY = charge passed in coulombs through the actual size of the test specimen 71 X = diameter in mm of the test specimen Y = thickness in mm of the test specimen a) Sliced concrete specimens b) PROOVEâit apparatus Figure 3.16 Rapid chloride ion penetration test setup 3.6.2.3.3 Sorptivity The water absorption test was performed in compliance with ASTM C1585 (2020) guidelines to investigate the susceptibility of concrete to water ingress over time. Two sliced concrete specimens with a diameter of 100 ± 6mm and thickness of 50 ±3mm were prepared, similar to the RCPT test except for the epoxy coating. The weight of the saturated samples was measured before the samples were conditioned in an environmental chamber at a relative humidity of 80 ±3% and a temperature of 50 ±2°C for 72 hours at 28 days. Then, the specimens were stored in sealable containers at 23 ±2°C for 15 days. The weight and the diameter of conditioned samples were measured, and the specimens were coated with epoxy on all sides except one end. Finally, the prepared specimens were weighed and placed into the pans on support devices with uncoated ends exposed to water, as shown in Figure 3.17. The water level was maintained about 1 to 3mm above the top of the support device. The mass of specimens was measured 72 after specific time intervals as per the ASTM C1585 (2020) standard, and the absorption rate was calculated using the following formula: I = mt /(a x d) Equation 3.6 where, I = absorption in mm mt = change in mass in grams at time t a = cross-sectional area of exposed end in mm2 d = density of water in gm/mm3 Figure 3.17 Sorptivity test setup 3.6.2.3.4 Elevated Temperature This test was performed to evaluate the behavior of cylindrical concrete specimens when exposed to elevated temperatures. Three cylinders having 100mm diameter and 200mm height from each concrete mix were exposed to a high temperature of 600 ± 10° C using Euclid CF 254 furnace at 28 days as shown in Figure 3.18(a) (Sevinç & Durgun, 2023). The rate of heating was maintained at 150°C/hour, and the specimens were kept at a temperature of 600 ± 10°C for one hour, as shown in Figure 3.18(b). Afterward, the specimens were left inside the furnace 73 to cool down and tested under compression after 24 hours. The performance of concrete to the elevated temperature was reported as residual compressive strength. a) Euclid CF 254 furnace b) Rate of heating curve Figure 3.18 Elevated temperature test 3.6.2.4 Microstructural Properties Similar to the mortar specimens, SEM and EDS were conducted to investigate the microstructural properties of concrete specimens such as ITZ, formation of CSH gel and 74 Ettringite. A Tescan Mira 3 XMU Scanning Electron Microscope was used to take SEM images with the help of secondary electrons. These images were used to analyze the effects of different replacement levels of various ingredients on the compressive strength of concrete. Then, SEM images were used for EDS Mapping with the help of Oxford Instruments X-Max EDS detector to study the elemental composition of concrete specimens. The small pieces from the core of cylindrical concrete specimens tested under compression at 28 days were utilized for the SEM and EDS analyses. All the specimens were coated with a 10 nm-platinum-palladium coating to reduce the risk of charging and produce high-quality images before conducting SEM and EDS analyses. 3.7 Summary This chapter demonstrated the research methodology adopted, encompassing the materials, mix design, test methods, and test setups to carry out this study. The procurement source and the physical properties of various materials used in mortar and concrete mixes were also discussed. Subsequently, the mix design proportions and sample preparation of mortar and concrete specimens were presented to explain the various replacement or substitution ratios considered in this study. Further, a detailed overview of the experimental testing program, including various test methods and their corresponding standards, shape, quantity, and testing age of specimens, was illustrated. Lastly, the test procedures and test setups involved in investigating the fresh, mechanical, durability, and microstructural properties of mortar and concrete mixes modified with wood ash and basalt powder were elaborated. 75 Chapter 4: Results and Discussions 4.1 General This chapter presents the experimental results of fresh and hardened properties, durability characteristics and microstructural analysis of mortar and concrete mixes modified with wood ash and basalt powder. The fresh properties of mortars were analyzed with the help of the flow value test. The compressive and flexural strength tests were performed to assess the mechanical properties of mortars. Likewise, the fresh properties of concrete were estimated by conducting a slump value test and an air content test. Compressive, flexural, and splitting tensile strength tests were carried out to determine the mechanical properties of hardened concrete mixes. Furthermore, the durability characteristics of concrete mixes were also investigated using F-T exposure, RCPT, sorptivity test, and elevated temperature exposure. Besides, the microstructural properties of various mortar and concrete mixes were studied with the help of SEM and EDS analyses. 4.2 Mortar The fresh properties of mortar mixes were determined by consistency from the flow value test. The hardened properties of mortars were evaluated in terms of compressive and flexural strength. SEM and EDS images obtained from SEM and EDS were used to examine the microstructural properties of mortars. 4.2.1 Flow Value Flow value defines the workability or the ease of mixing, placing, compacting, and finishing the surface of mortar mix. Table 4.1 shows the flow values of various mortar mixes. It can be observed that the flowability or consistency of mortars was considerably reduced when basalt 76 powder was incorporated as sand replacement. The fluidity of mortars was found to be decreased by 65% and 79.3% with reference to the control mix at 50% and 100% sand replacement ratios, respectively. Dobiszewska & Barnes (2020b) also observed similar decreasing trends at smaller replacement ratios due to the higher specific surface area of micro-fines present in basalt powder than sand. Conversely, the consistency of mortars was slightly increased with the partial replacement of cement with basalt powder. The consistency was increased by 7.3%, 13%, and 35% compared to the control mix at 10%, 20%, and 30% cement substitution levels, respectively. An identical improvement in consistency with basalt as a cement substitute in the presence of a superplasticizer was also noticed (Uncik & Kmecova, 2013). It may be due to the coarser particle size of basalt than cement, causing reduced water demand to wet the particles' surface and eventually enhancing the consistency. Further, the mortar mixes prepared by introducing wood ash as a partial replacement of cement in addition to the basalt powder as a sand substitute were found to have reduced flow diameters. Similarly, Cheah & Ramli (2012) also stated a reduction in flow diameter with the addition of wood ash as a cement substitute and attributed it to the irregularly shaped and unburnt wood ash particles with higher specific surface area than cement. The mortars prepared with 50°C and 90°C hot mixing water were reportedly stiff with zero flowability. The decrease in workability with the increase in mixing water temperature was also concluded by (Naganathan & Mustapha, 2015). The flow diameters or flow values of various mortar mixes are illustrated in Figure 4.1. The pictures of BC20 and BC 30 were taken before the 25 drops instead of post compaction. In all the mortar mixes, the w/c and air-entraining admixture were kept constant at 0.485 and 1 ml, respectively. However, the dosage of HRWRA was increased with the increase in replacement levels. 77 Table 4.1 Flow values of various mortar mixes Mix Flow Value (%) HRWRA (ml) Control 61.5 0 BS50 21.5 1 BS100 12.75 3 BC10 66 0 BC20 69.5 0 BC30 83 1 BAC10 40.5 8 BAC20 23 12 HBAC10@50 0 8 HBAC20@50 0 12 HBAC10@90 0 8 HBAC20@90 0 12 a) Control b) BS50 c) BS100 78 Figure 4.1 Flow diameters of various mortar mixes d) BC10 e) BC20 f) BC30 79 4.2.2 Mechanical Properties 4.2.2.1 Compressive Strength Compressive strength is a fundamental property in assessing the structural integrity and load-bearing capacity of mortar mixes. This section presents the compressive strength results for various mortar mixes at different curing ages and discusses their performance in relation to material composition and microstructural characteristics. The compressive strength results of various mortar mixes are presented in Figure 4.3. The early strength of mortar at 7 days was increased initially at smaller sand replacement levels up to 5%, as indicated in Figure 4.3(a). Then, the 7-day strength of the mortar was dropped with the further addition of basalt powder up to 20%. However, the compressive strength was still comparable to the control mix. Furthermore, the 7-day strength of mortar started increasing again at 40% and higher replacement levels with reference to the control mix. The 7-day strength of mortar at 5% and 100% replacement levels was improved by 68.15% and 60.81%, respectively. A similar strength pattern was observed in the compressive strength of mortar mixes with basalt powder as a sand substitute after 28 and 56 days. The 28-day compressive strength at 5% and 100% replacement levels were increased by 64.54% and 64.32%, respectively. Likewise, the 56-day compressive strength of mortar mixes with 5% and 100% replacement of sand with basalt powder was found to be 24.78% and 14.14% higher than the control mix. The compressive strength of mortar at smaller replacement ratios was increased due to the filling of voids by the particles of basalt powder fines, thus producing a denser matrix. Besides, the strength presented a downward trend up to 20% substitution levels, which may be due to the lack of coarse particles to produce the matrix structure caused by the dispersion of sand. However, the improvement in compressive strength at all curing ages with the further replacement of sand 80 with basalt powder may be due to the pozzolanic behavior of basalt powder. The compressive strength of control mixes with and without AEA was also compared. It was observed that the incorporation of AEA in mortar considerably lowered the early-age compressive strengths. On the other hand, Figure 4.3(b) shows that the compressive strength of mortars with 5% basalt powder as a cement substitute was found to be 40.22%, 12.42%, and 23.73% higher than that of the control sample at 7, 28, and 56 days, respectively. This may be due to the filling mechanism of basalt powder, which results in the better interlocking of particles. Further addition of basalt powder replacing cement presented a declining pattern at all replacement ratios and curing ages. This may be due to the dispersion of cement grains leading to a lack of binding material and optimum pozzolanic content, thus causing poor bonding between the particles (Serhat and Bilal, 2024). As shown in Table 3.3, the pozzolanic content of basalt powder is lower than the specified limit of 70% (ASTM C618, 2023). Therefore, the basalt powder investigated in this study is not suitable for use as a binding material at higher replacement ratios. However, the compressive strengths at a 10% replacement level were comparable to those of the control sample. Also, the compressive strength was slightly lower than that of the control mix, up to a 20% replacement ratio. Afterward, wood ash was introduced in the mortar mixes as a replacement for cement, and basalt powder was added as a substitute for sand. The highest compressive strength was produced by mortar mix with 5% wood ash replacement at 56 days, as illustrated in Figure 4.3(c). The strength of mortar with 5% wood ash was 19.8% higher than the control mix at 56 days. In contrast, the early strength at the same replacement ratio was slightly lower than the control mix. However, the early strength developed in mortar mixes at 10% and 15% wood ash replacement was also found to be 54.6% and 38.5% at 7 days and 25% and 8% at 28 days, 81 respectively, higher than the control sample. This may be due to the filling mechanism of wood ash particles producing denser microstructure. The compressive strengths were reduced with increased wood ash content in the mortar mixes at all curing ages. The lowest compressive strength was reported in mortar mixes with 30% wood ash content at all curing ages. The primary reason behind this could be the excessive formation of hydrates due to the pozzolanicity of wood ash and basalt powder aggravated by the lack of particles to develop bond strength. The 7-day compressive strengths of mortar mixes with 25% and 30% could not be tested as the samples were still wet even after 7 days and could not develop any strength, as shown in Figure 4.2. This may be due to slow strength development in mortars prepared with wood ash, as reported in the literature. a) BAC25 b) BAC30 Figure 4.2 7-day wet samples of mortar mixes The literature suggests that using hot mixing water in hydraulic cement mixes accelerates the rate of hydration, resulting in rapid strength development at early ages and reduced strength at later ages. The literature also reports that this reduction in strength can be mitigated with the help of SCMs in the mix. Since the mortar mixes with higher wood ash content and normal tap water exhibited slow strength development, these mortars were also investigated with varying mixing water temperatures, i.e., 50°C and 90°C. The inclusion of hot mixing water positively impacted the rapid strength development, particularly in mortars with higher wood ash content at early ages, as shown in Figure 4.3(d) and Figure 4.3(e). However, the strength of mortars 82 with hot mixing water demonstrated a decreasing trend with the addition of wood ash compared to the control sample for all curing periods, as depicted in Figure 4.3(f), Figure 4.3(g), and Figure 4.3(h). This may be due to the strength reduction due to retarded subsequent hydration and uneven distribution of hydrates, being more dominant than the rapid strength development. The least reduction in compressive strength at 50°C mixing water temperature was found in mortars with a 5% wood ash replacement ratio. The strength reduction at 5% replacement was obtained as 51.1%, 39.2%, and 53.6% after 7, 28, and 56 days, respectively, compared to the control mix, as shown in Figure 4.3(d). Similarly, in the case of mortars prepared with 90°C mixing water temperature, the strength reduction was lowest at a 5% substitution ratio at 58.2%, 46.8%, and 48.8%, respectively, after 7, 28, and 56 days as shown in Figure 4.3(e). On the other hand, the strength reduction was diminished in mortars with hot mixing water and higher wood ash content at later ages. It is clearly evident from Figure 4.3(h) that the mortar with 30% wood ash content regained compressive strength by 26% and 4% at 50°C and 90°C mixing water temperatures, respectively, compared to the mortars with lower wood ash content after 56 days. This can be attributed to the mitigation of strength reduction by the addition of SCMs, as reported in the literature. 83 Figure 4.3 Compressive strength of mortar mixes a) Basalt used a sand replacement b) Basalt used as a cement replacement c) Wood Ash as a cement replacement and Basalt as a sand substitute d) Mortar mixes prepared with 50°C hot mixing water e) Mortar mixes prepared with 90°C hot mixing water f) 7-day compressive strength at different mixing water temperatures g) 28-day compressive strength at different mixing water temperatures h) 56-day compressive strength at different mixing water temperatures 84 4.2.2.2 Flexural Strength The flexural strength of mortar mixes is the ability to resist the loads without failure in bending. The flexural strength of various mortar mixes at 28 days is presented in Figure 4.5. It can be stated from Figure 4.5(a) that the flexural strength was increased by 43.9% and 60.1% when the basalt powder was induced as sand in mortars at 50% and 100% replacement levels. Similar to the compressive strength, this may be due to better particle packing and denser matrix structure. Conversely, it can be derived from Figure 4.5(b) that the cement replacement with basalt powder decreases the flexural strength by 2.9%, 11.8%, and 25.8% at substitution ratios of 10%, 20%, and 30%, respectively. This decrease may have occurred due to the decrease in cement content and subsequently resulting in reduced bond strength. In ternary mortar mixtures, i.e., BAC, the strength was increased only up to 10% wood ash content, as shown in Figure 4.5(c). The flexural strength of BAC10 was found to be 21.5% higher than the control mix. However, the samples with 20% wood ash, i.e., BAC20, were broken during demolding, as shown in Figure 4.4, due to slow strength development. This weak early strength can be improved by modification of mortar mixes with alternative admixtures, such as hardening accelerators or hot water curing for rapid early strength (Naganathan & Mustapha, 2015). Therefore, the BAC mixes were prepared again with hot mixing water, i.e., 50°C and 90°C. Similar to the compressive strength of mortar, there was a drop in the flexural strength of hot mixing water mortars compared to the tap water. The flexural strength of hot mixing water mortars with 10% wood ash content, i.e., HBAC10, was reduced by 5.3% and 14.2% at 50°C and 90°C, respectively, compared to tap water. Nevertheless, it was noticed that there was a gain of strength of 24.6% at 90°C than 50°C at higher wood ash content, i.e., 20% as reported in the literature. 85 Figure 4.4 Broken samples of BAC 20 while demolding a) Basalt used as a sand replacement b) Basalt used as a cement replacement c) Wood Ash as a cement replacement and Basalt as a sand substitute d) 28-day flexural strength at different mixing water temperatures Figure 4.5 Flexural strength of mortar mixes at 28 days 4.2.3 Microstructural Properties This section examines the influence of wood ash and basalt powder on the microstructure of mortar mixes using SEM and EDS. The presence and distribution of hydration products such as (CSH) and (CH) are analyzed to correlate with the mechanical and durability properties. 86 The observations of SEM-EDS analyses to determine the influence of wood ash and basalt powder on the microstructural properties of various mortar mixes are shown in Figure 4.6 to Figure 4.9. The formation of hydrates, i.e. Tobermorite or CaO-SiO2-H2O or CSH and Portlandite or Ca(OH)2 or CH after 28 days, was investigated in SEM images to assess microstructural properties. The presence of CSH, CH and ettringite needles was indicated using yellow, blue and red arrows, respectively. It can be observed from Figure 4.6 that the addition of basalt powder as fine aggregate resulted in the uniform spread of CSH adhering closely to the particles of basalt powder compared to the control mix and, subsequently, a denser microstructure and improved strength. It is also visible in Figure 4.6 that the CSH growth was lower in BS50 and higher in BS100 compared to the control mix, and it aligns with compressive strength results. On the other hand, when basalt powder was used as a cement replacement, the formation of CSH was adequate to cover all the particles only at lower replacement ratios, as presented in Error! Reference source not found.. Dobiszewska et al. (2018) also reported similar densification of cement matrix due to the heteronucleation of CSH gel on the particles of basalt powder followed by stronger ITZ. However, at higher substitution levels, the lack of sufficient hydration compounds results in an increased porosity, as evident in Error! Reference source not found., resulting in reduced strength. This conforms to the decrease in compressive strength of mortars while basalt is used as a cement replacement. Additionally, the formation of ettringite needles was also observed at higher substitution levels. With the incorporation of wood ash as cement replacement in addition to the basalt powder as sand substitute in mortar mixes, the formation of CSH at lower wood ash content was higher than the control mix, resulting in lesser voids, and this can also be validated from the compressive strength of BAC10 after 28 days. At higher wood ash content, the tobermorite gel 87 produced in the cementitious matrix was insufficient to cover all the particles. However, a comparative analysis of Figure 4.8 and Figure 4.9 indicates that the CH or portlandite crystals in BAC20 were present in higher amounts compared to the BAC10. This may be the major reason behind the reduced strength since they are responsible for weakening the transition zones and, hence, the overall cementitious matrix (Rumman et al., 2023). Moreover, this can be attributed to the slow rate of hydration with the inclusion of wood ash, as further CSH can be produced with the depletion of CH (Kunther et al., 2017). Along the same note, the CSH formation increased considerably when the mortars engineered with wood ash and basalt powder were prepared with hot mixing water. The CSH growth was more dominant in mortars prepared with mixing water at 90°C compared to 50°C as illustrated in Figure 4.8 and Figure 4.9. This can be attributed to the accelerated rate of hydration due to hot mixing water. The ettringite needles were also visible in mortars prepared with 90°C mixing water. Further, the ratio of calcium to silicate (Ca/Si) for CSH gel was evaluated with the help of EDS analysis of mortars. It was observed that compressive strength increased with the decrease in Ca/Si ratio when basalt powder was used as cement replacement. A similar relationship was also reported by Kunther et al. (2017). However, this relationship was not satisfied when basalt was used as sand replacement. In the case of wood ash, this relationship was fulfilled only at lower replacement levels. Likewise, the relationship was also met in mortars prepared with hot mixing water at low wood ash content. 88 Figure 4.6 SEM-EDS of mortar mixes using basalt as sand replacement 89 Figure 4.7 SEM-EDS of mortar mixes using basalt as cement replacement Figure 4.7 SEM and EDX of various mortars with bas lt powder as cement replacement 90 Figure 4.8 SEM-EDS of mortar mixes with varying mixing water temperatures 91 Figure 4.9 SEM-EDS of mortar mixes with varying mixing water temperatures 92 4.3 Concrete 4.3.1 Fresh Properties The fresh properties of concrete play a crucial role in determining its workability, ease of placement, and long-term performance. The fresh properties of all concrete mixes, such as workability, were measured in terms of slump and air content, as listed in Table 4.2. HRWRA was used to moderate the water demand spike due to the increased surface area of SCMs, as discussed in the literature. It can be derived from the M3 and M6 mixes that the wood ash negatively influenced workability and significantly increased the demand for water reducers. Similarly, the workability of concrete was also reduced with the addition of basalt powder, as reflected in the M1 and M4 mixes. M1 and M3 exhibited higher slump values than M0 due to the addition of water reducer. The lowest slump values among all the mixes considered were obtained from the M5 and M6 mixes. Table 4.2 Fresh properties of concrete Mix HRWRA (ml) HRWRA (%) AEA (ml) AEA (%) Slump (mm) Air Content (%) M0 0 0 5 0.028 190 6.1 M1 10 0.063 4.5 0.029 230 8 M2 22 0.133 7 0.042 190 4.2 M3 35 0.211 9 0.054 205 11.5 M4 11 0.066 5 0.030 175 10 M5 11 0.066 6 0.036 60 4.5 M6 40 0.392 10 0.070 50 9 AEA was used to enhance the F-T performance of concrete by uniformly distributing the air spaces in the cement matrix. The need for air entrainment was increased slightly with the higher 93 dosage of wood ash, which can be inferred from the comparison of M1-M3 and M4-M6 mixes. However, the increment of basalt powder hardly affected the air content, as visible in M0, M1, and M4 mixes. 4.3.2 Hardened Properties The hardened properties of various concrete mixes were evaluated in terms of mechanical strengths for different curing periods, such as resistance to crushing loads without failure from compressive strength, resistance to bending from flexural strength, and capacity to withstand pulling forces from splitting tensile strength. Furthermore, the failure patterns of various concrete mixes were also discussed. 4.3.2.1 Compressive Strength The compressive strength of various concrete mixes for different curing ages is shown in Figure 4.10. It can be analyzed from the graph that the strength of all concrete mixes depicts an increasing pattern with the curing time. Besides, the compressive strength was increased up to 10% replacement of cement with wood ash while using basalt powder as a sand substitute partially or fully. The improvement in compressive strength was highest in M2 and M5, i.e., compared to the M0, i.e., control mix, for all curing periods. It was evaluated as 13.5%, 9.7%, 18.2%, and 19.4% for M2 and 9.4%, 5.6%, 13.7%, and 15.9% for M5 mixes after 7, 28, 56, and 90 days, respectively. This may be due to the combined action of the filling mechanism and the formation of secondary hydrates by the addition of basalt powder and wood ash, respectively. However, the lowest compressive strength was recorded at a 20% wood ash replacement ratio in M3 and M6 mixes. The strength reduction was assessed as 40.1%, 41.6%, 39.2%, and 37.2% in M3 and 57.5%, 55.8%, 52.9%, and 53.4% in M6 mixes after 7, 28, 56, and 90 days, respectively. This strength reduction at higher proportions of wood ash can be 94 attributed to the reduced cement content and, subsequently, decreased bond strength. The compressive strength of M4 was evaluated higher than M1 due to an increase in the pozzolanic content from basalt powder, replacing sand completely as fine aggregate. On the other hand, the strength of M5 was assessed to be slightly lower than M2. It may be due to the formation of excess hydrates due to the combined pozzolanic content of wood ash and basalt powder, resulting in the scarcity of particles for bonding. This effect was found to be more pronounced in M3 and M6 mixes. It can be concluded from these results that the strength of concrete mixes with basalt as a partial or full substitute of sand was comparable to the control mix. Additionally, incorporating wood ash as cement influenced the strength positively at lower replacement levels. However, at higher replacement levels, wood ash was detrimental to the compressive strength of concrete. Figure 4.10 Compressive strength of various concrete mixes 4.3.2.2 Flexural Strength Error! Reference source not found.Figure 4.11 displays the flexural strength of concrete mixes at 28 days. Concrete mixes with 100% basalt substitution as sand and low wood ash content performed better under flexure than all other mixes. The modulus of rupture of the M4 and M5 mixes was observed to be 20.1% and 21.8% higher than the M0 mix. Similarly, M2 95 with 10% wood ash performed the best among the mixes, partially substituting basalt as fine aggregate. The modulus of rupture of the M2 mix was 12.8% higher than the M0. Also, it should be noted that the rupture strength of M3 was 6.2% higher than M0. The major reason behind the increased flexural strength in concrete mixes can be credited to microfines present in basalt powder filling the voids and improving the microstructure. Due to the delayed hydration of wood ash, the effect of wood ash on flexural strength at 28 days cannot be pronounced. However, the filling mechanism of wood ash can still be noticed. On the other hand, the flexural strength of M6 was found to be 8.7% lower than M0. This may be due to incomplete hydration at higher replacement ratios. This is subsequently followed by weak ITZ and poor bond strength. Further, it can be noticed that the flexural strength of M4 was higher than M1, similar to the compressive strength. Conversely, the flexural strength of M2 was lower than M5. This may be due to a different degree of compaction during concrete casting, i.e., higher compaction effort in the case of M5 than M2. Therefore, it can be established that a higher proportion of wood ash as cement in combination with partial substitution of basalt powder as fine aggregate behaves better than the control mix under flexure. Figure 4.11 Flexural strength of concrete mixes at 28 days 96 4.3.2.3 Splitting Tensile Strength The splitting tensile strength test is an indirect method to evaluate the resistance of concrete against tensile stresses. The tensile strength of concrete is generally considered negligible in the mix design. However, it plays a crucial role against cracks and, thus, the serviceability and durability of concrete. The splitting tensile strength of the concrete mixes after 28 days of curing is shown in Figure 4.12. The tensile behavior of the engineered concrete mixes was found to be quite identical to the flexural response. However, the highest split tensile strength was measured in the mix with 50% basalt powder as fine aggregate and 10% wood ash content. The tensile strength of M2 was found to be enhanced by 16.9% compared to M0. The strength improvement of M4 and M5 mixes was determined to be 16.1% and 15.2% higher than M0. Similar to the flexural response, the M3 concrete mix with a higher amount of wood ash developed 6.4% higher tensile strength than the control. Besides, the split tensile strength of M1 and M6 was noticed to be 6.1% and 2% lower than the control mix. Figure 4.12 Splitting tensile strength of concrete mixes at 28 days 4.3.2.4 Failure Patterns Failure pattern analysis provides insight into the structural integrity, failure mechanisms, and material behavior of concrete under axial compression. Understanding these patterns helps in 97 evaluating the effectiveness of different mix designs and their ability to withstand loads before failure. This section discusses the observed failure modes of cylindrical concrete specimens observed in this study. Figure 4.13 shows the failure pattern of cylindrical specimens prepared from various concrete mixes under axial compression. The failure patterns were categorized as per ASTM C39/C39M (2023). Cone and split failure similar to ASTM Type 2 was observed in the M0, i.e., control mix. A combination of cone and shear failure similar to ASTM Types 1 and 4 was demonstrated by M1 and M4 mixes. The M2 mix exhibited side fractures at the top while remaining intact at the bottom, similar to ASTM Type 5, suggesting that the load distribution was uneven. This behavior is likely due to the increased replacement of cement with wood ash, which might have weakened the bond strength at the upper portion of the specimen while maintaining a relatively stronger base. M3 suffered a combination of ASTM Types 4 and 5, i.e., slant shear failure with side fractures at the bottom. M5 exhibited columnar vertical cracking similar to ASTM Type 3. M6 sustained a combination of cone and shear failure similar to ASTM Types 1 and 4. This indicates that while the mix maintained some level of cohesion, the presence of wood ash and basalt powder may have altered the bond strength and fracture mechanics within the matrix. The shear failure suggests localized weak zones in the ITZ, potentially due to incomplete hydration or reduced paste-aggregate bonding at higher replacement levels. Figure 4.13 Compressive failure modes of various concrete mixes at 28 days 98 4.3.3 Durability Properties The durability of all the concrete mixes was evaluated with the help of F-T exposure, RCPT, sorptivity test, and exposure to elevated temperatures. The results obtained are discussed below in terms of surface deterioration, mass change and residual flexural strength from F-T exposure, rate of water absorption due to capillary rise from sorptivity test, resistance to chemical attack from RCPT, and reduction in compressive strength after elevated temperature exposure. 4.3.3.1 Freeze-Thaw Exposure This section evaluates the F-T resistance of modified concrete mixes containing wood ash and basalt powder by analyzing surface deterioration, mass change, and residual flexural strength. Figure 4.14 compares the beam specimens of all concrete mixes after 150 cycles of F-T exposure. All the beam specimens survived the 150 F-T cycles without any failure, i.e., large cracks. However, the surface deterioration was severe in specimens with higher wood ash content, such as M3 and M6. Surface scaling and spalling were observed in these mixes, resulting in coarse aggregate exposure. The increased surface scaling and mass loss in M3 and M6 may be attributed to their higher porosity and weaker ITZ, as observed in the SEM analysis. The presence of unreacted wood ash particles may have contributed to the deterioration by promoting water absorption and ice expansion in the paste matrix. It can be analyzed from M2-M3 and M5-M6 mixes that the surface damage was escalated with the addition of wood ash compared to M1 and M4 mixes without wood ash. Likewise, the extent of damage was also slightly increased with the substitution of basalt powder compared to the partial replacement of sand. The M1 mix performed the best among all mixes, with the lowest surface damage, followed by the control mix. 99 The flexural strength of all the concrete mixes was evaluated after 150 cycles of F-T and compared with the beam specimens without F-T exposure. Figure 4.15 illustrates that residual flexural strength decreased for all mixes except M0 and M2, which showed minor strength gains. The flexural strength of M0 and M2 was increased by 5.1% and 2.9%, respectively. This slight increase in strength could be attributed to secondary hydration reactions filling microcracks, as well as the entrapped air voids acting as stress buffers, delaying crack propagation. The highest strength reduction of 15.1% was observed in the M5 mix specimens. On the other hand, the change in mass was observed to increase initially in all the concrete mixes, as shown in Figure 4.16. This may happen due to the moisture uptake by poorly connected capillary pores. The change in mass was reduced later after these pores were saturated Z. Liu and W. Hansen (2016). The M4 mix experienced the highest change in mass among all mixes. The M3 mix also suffered a considerable change in mass due to severe surface deterioration, causing material loss. The slight increase in mass change in M6 after 120 cycles may be due to internal cracking, resulting in more water absorption. From all the aforementioned parameters, i.e., surface deterioration, change in mass, and residual flexural strength, it can be concluded that the M2 mix offered better resistance to F-T exposure compared to all other mixes. 100 Figure 4.14 Deterioration of freeze-thaw specimens after 150 cycles M0 M1 M2 M3 M4 M5 M6 101 Figure 4.15 Residual flexural strength after 150 F-T cycles Figure 4.16 Change in mass after 150 F-T cycles 4.3.3.2 Rapid Chloride Ion Penetration Test The RCPT assesses the permeability of concrete to determine the resistance against chloride ions penetrability of concrete exposed to deicing salts or marine water conditions. Figure 4.17 represents the chloride ion penetration in all the concrete mixes in terms of the average charge passed through the specimens. Based on the average charge passed, all the concrete mixes under investigation fall under the high chloride ion penetrability category except M5, as per ASTM C1202 (2022). The concrete mix M5 developed the highest chloride penetration resistance and can be categorized as having moderate chloride ion penetrability. The average charge passed through M5 was 34.5% lower than the control mix. Further, it was observed in M1-M4, M2-M5, and M3-M6 mixes that the resistance to chloride penetration increased with the increase of basalt powder. This may be due to the filling effect of micro fines present in basalt powder, thus reducing the pores and permeability of concrete. On the other hand, the mixes yield good resistance at lower wood ash content, but with the increase in wood ash content, the resistance decreased, as visible in the M2-M3 and M5-M6 mixes. This may be due to the pozzolanicity of wood ash intensifying the particle packing mechanism at lower wood ash levels, resulting in a dense cement matrix. However, at higher wood ash content, the 102 particle packing effect was outperformed due to the lack of cement particles, thereby causing more voids in the mix and consequently increasing the permeability of concrete (Siddique et al., 2019). Figure 4.17 Chloride ion penetration in concrete mixes 4.3.3.3 Sorptivity Sorptivity evaluates the rate of water absorption due to capillary rise with time and, thus, the resistance of concrete to deterioration when exposed to moisture or wet conditions. The rate of water absorption due to capillary rise (or sorptivity) with time in all concrete mixes is plotted in Figure 4.18. The initial and secondary water absorption rate was observed to increase with the increase in wood ash content. The highest rate of water absorption was encountered in M3 and M6 mixes. This may be attributed to the hydrophilic nature of wood ash (Hussain et al., 2017). Another contributing factor could be improper compaction due to low workability at higher wood ash content, increasing the impermeable pores in the mix (Siddique et al., 2019). The addition of basalt powder was found to reduce the water absorption rate, specifically in M1 and M4 mixes. This may be due to the presence of micro fines in basalt powder filling the void spaces and thus decreasing the capillary cavities of concrete (Binici et al., 2020). This can also be verified from M2 and M5 concrete mixes with the same wood ash content but 103 increasing replacement ratios of basalt powder. M5 with 100% basalt powder substitution sustained better water ingress resistance than M2 with 50% basalt powder. Figure 4.18 Sorptivity of concrete mixes 4.3.3.4 Elevated Temperature Exposure Exposure to elevated temperature determines the behavior or response of concrete at high temperatures in terms of strength reduction or failure type. Figure 4.19 and Figure 4.20 depict the residual compressive strength and the percentage reduction of all the concrete mixes at elevated temperatures compared to compressive strength at 28 days. The results show that the loss of compressive strength at high temperatures is lower in all the considered mixes compared to the control mix. The M6 mix offered the highest endurance to elevated temperatures, followed by the M3 mix. The strength reduction of the M6 and M3 mixes was 44.3% and 23.2% lower than the control mix. This can be referred to as the impermeable pores, associated with the sorptivity, which helped release internal vapor pressure build-up due to the water vaporization beyond 100°C (Uysal, 2012). It can also be stated from the comparison of M1-M4, M2-M5, and M3-M6 mixes that adding basalt powder enhances the performance of 104 concrete subjected to elevated temperatures. The compressive strength loss was reduced by 10.4% in M4, 9.7% in M5, and 21.1% in M6 compared to M1, M2, and M3 mixes, respectively. This may be because basalt is an igneous rock formed by the cooling and solidification of magma and thus offers better resistance to high temperatures (Ãelikten & Baran, 2024b). Figure 4.19 Residual compressive strength of concrete at elevated temperatures Figure 4.20 % reduction in compressive strength of concrete at elevated temperatures 4.3.4 Microstructural Properties This section defines the metamorphosis of concrete mixes augmented with wood ash and basalt powder at a microscopic level with the help of images or X-rays. The SEM images or EDS X-rays were analyzed to determine the development of ITZ, formation of cement hydrates and elemental composition of concrete. Figure 4.21 shows the results of SEM-EDS analyses of various concrete mixes prepared with wood ash as cement replacement and basalt powder as a sand substitute. The presence of CSH, CH and ettringite needles was indicated using yellow, blue and red arrows, respectively. It can be inferred from Figure 4.21 that the formation of tobermorite gel or CSH in M2 and M5 mixes was significantly higher than that of the other concrete mixes, resulting in a dense microstructure of a cementitious matrix. This aligns with the increased compressive strength of these mixes after 28 days. It was also noted from comparing M1-M4, M2-M5 and M3-M6 mixes that with the increase of basalt powder, the Figure 4.16a) Residual compressive strength of concrete at elevated temperatures Figure 4.16b) %reduction in compressive strength of concrete at elevated temperatures 105 CSH growth increased due to the pozzolanic content of basalt powder. On the contrary, the CSH growth was higher in concrete mixes with lower wood ash content, such as M2-M3 and M5-M6. Similar to mortar mixes, the portlandite crystals or CH were also observed in the concrete mixes with higher wood ash content due to the slow rate of hydration. The evolution of ettringite needles was observed in all the concrete mixes. Furthermore, the EDS analysis was performed on the SEM images to determine the Ca-Si ratio. According to Kunther et al. (2017), a low Ca-Si ratio demonstrates a high strength. This relationship of Ca/Si ratio and compressive strength was established between M1-M3, M1-M4, and M4-M5-M6 mixes. The relationship was not fulfilled in M1-M2-M3 mixes, possibly due to the many variables in ternary mixtures. 106 107 Figure 4.21 SEM-EDS of various concrete mixes 4.4 Summary This chapter illustrated and analyzed experimental results to evaluate the influence of basalt powder and wood ash on the fresh, mechanical, durability, and microstructural properties of mortar and concrete mixes. When basalt powder was incorporated as a sand replacement, the consistency of mortars was reduced. However, the strength of mortars was found to be improved at 5% and 100% replacement ratios. The CSH formation was uniform, resulting in a dense microstructure. On the other hand, using basalt powder cement replacement improved the consistency; however, the strength decreased. The CSH growth was also inadequate at higher replacement levels resulting in reduced strength. With the introduction of wood ash as 108 cement replacement in combination with basalt powder as a sand substitute, the consistency and strength of mortars were found to be slightly lower than the control mix at low wood ash content. The CSH formation was also reported, which resulted in lesser voids. However, the consistency and strengths of the mortar were reduced considerably, and a slow strength development was observed at higher wood ash content due to the slow rate of hydration caused by wood ash. The CH crystals were also present in higher amounts, causing the weakening of ITZ. To accelerate the hydration process, two different temperatures, i.e., 50°C and 90° C of mixing water, were examined. The hot mixing water enhanced strength development at early ages; however, the strength at later ages was found to be reduced. This strength reduction was reported to be less pronounced in mixes with higher wood ash content. Moreover, the strength of mixes with higher wood ash content at later ages, i.e., 56 days was found to be higher than the control mix. The CSH growth was found to be higher in mortars at 90°C than at 50°C. In the case of concrete mixes, the M2 mix consisting of 10% wood ash as SCM and 50% basalt powder as fine aggregate outperformed all other mixes, followed by the M5 mix with 10% wood ash and 100% basalt powder. The increase in basalt powder from 0%, 50%, and 100% in M0, M1, and M4 was impacted positively by the filling mechanism due to the presence of fines. However, the increase of wood ash content from 0%, 10%, and 20% in M0-M1-M2 and M4-M5-M6 was found to be detrimental to the various properties of concrete. As far as the mechanical and durability properties are concerned, M2 mix with 10% wood ash as cement replacement and 50% basalt powder as sand substitute performed best among all the mixtures investigated and was found to be the most optimal option. All the tests conducted were important to determine the impact of wood ash and basalt powder on concrete performance under different conditions. However, the most critical test considered was 109 compressive strength since all the mixes were designed to achieve certain compressive strength at 28 days in accordance with the CSA standard. 110 Chapter 5: Conclusions and Recommendations 5.1 General This chapter summarizes the performed study's conclusions, outcomes, limitations, and recommendations for future research. The fresh, mechanical, and microstructural properties of mortar and concrete mixes were investigated to determine the possible application of recycled constituents in manufacturing disaster-resilient low-carbon mixes. The durability properties of various concrete mixes were also examined. Based on the results obtained, it can be stated that wood ash and basalt powder performed well as cement and sand substitutes in terms of mechanical and durability parameters. These findings contribute to sustainable construction by reducing reliance on conventional cement and aggregates while improving specific mechanical and durability properties of concrete. This study provides valuable insights for researchers, engineers, and policymakers seeking low-carbon alternatives for structural and non-structural applications. 5.2 Conclusions The vital insights extracted from this study can be described as below: 1. The consistency of mortars decreased when sand was replaced with basalt powder. Conversely, it increased when basalt was used as a cement substitute. The consistency of mortars was also reduced with the addition of wood ash. The mortars prepared with hot mixing water were reportedly stiff with zero flowability. 2. The compressive strength of mortars increased at all ages with the replacement of sand with basalt powder due to improved particle packing and potential pozzolanic activity, which enhanced the formation of CSH. However, the compressive strength of mortars declined with the substitution of basalt powder for cement. 111 3. The incorporation of wood ash as cement improved the compressive strength at lower replacement ratios; however, the strength was reduced at higher wood ash content. Besides, slow strength development was observed with the addition of wood ash due to the low rate of hydration. 4. The flexural strength of mortars augmented with basalt powder as fine aggregate was enhanced. However, it dropped when basalt powder was used as a cement replacement. Further, the flexural strength of mortars improved with the inclusion of wood ash at low replacement ratios. 5. The use of hot mixing water resulted in rapid strength development but reduced strength in mortar mixes with low wood ash content. However, the strength reduction was diminished in mortar mixes with high wood ash content. 6. The workability of concrete was impacted negatively by the incorporation of basalt powder and wood ash. 7. The addition of basalt powder improved the mechanical properties of concrete, such as compressive, flexural, and splitting tensile strengths, whereas wood ash was effective only at lower replacement levels. 8. The combination of partial substitution of basalt powder as sand and low wood ash content as cement was found to amplify the durability of concrete against 150 cycles of F-T exposure. 9. The concrete mix M5 developed the highest chloride penetration resistance and can be categorized as having moderate chloride ion penetrability. The average charge passed through M5 was 34.5% lower than the control mix. 112 10. The incorporation of basalt powder at all replacement levels considerably reduced the sorptivity of concrete mixes. However, the addition of wood ash significantly increased the rate of water absorption due to capillary rise. 11. The combination of basalt powder and wood ash at all replacement ratios was found to strengthen the performance of concrete at elevated temperatures. The M6 mix offered the highest endurance to elevated temperatures, followed by the M3 mix. 12. The formation of CSH was observed to be increased with the increase of basalt powder in mortar and concrete mixes. However, the CSH growth was higher at low wood ash content. 13. The combination of basalt powder as fine aggregate and low wood ash as cement showed superior F-T resistance due to enhanced matrix density and reduced water absorption. However, high wood ash content led to increased mass loss and surface scaling. 5.3 Outcomes and Contributions The experimental results of this study clearly show that waste products from the timber and mining industries have the potential to develop a novel cementitious composite that would be affordable, reduce the carbon footprint, and effectively manage waste. This composite can be successfully used for non-structural applications such as modular wall panels, pavement blocks, and kitchen slabs. Further research could explore the feasibility of using optimized mixtures for structural elements such as slabs and beams, particularly in low-rise buildings. The key contribution of this study includes the combined application of wood ash and basalt powder to develop a low-carbon cementitious composite with enhanced strength and durability properties. 113 5.4 Limitations Based on the experiments performed in this study, the following limitations were identified in this study: 1. Two different admixtures were used as water reducers in mortar and concrete mixes. Sika Viscocrete-6100 and Sika Viscocrete-2100 were used as high-range water reducers in mortar and concrete mixes, respectively. Therefore, the properties of mortars cannot be linked to the properties of concrete mixes. 2. Since wood ash properties were sourced from prior research, variations in chemical composition (for example; carbon content, fineness) could have influenced the pozzolanic activity and setting behavior of concrete. 3. Concrete specimens were compacted by two individuals who aimed to maintain uniform compaction effort, but minor inconsistencies may have occurred. 4. Due to the limited capacity of the mixer, concrete mixes were prepared in three separate batches. Each batch was designated for a specific number and type of specimen, as shown in Table 3.4. 5. Measurements of dynamic modulus and change in length after F-T exposure were not conducted due to equipment limitations. 6. Non-laboratory-grade kosher salt was used in the RCPT because lab-grade sodium chloride was unavailable. 7. During elevated temperature exposure, specimens were placed in three consecutive rows in the furnace. The corner rows were exposed to slightly higher heat than the middle row due to the heating coil placement, though this effect was likely negligible at 600°C. 114 5.5 Recommendations for Future Research This study focused on developing disaster-resilient low-carbon mortar and concrete utilizing the waste from timber and mining industries. Various aspects, including mechanical, durability, and microstructural properties, were investigated in this study. However, there remains significant scope for further research and optimization. The recommendations for future studies are summarized as follows: 1. The target strength of concrete in this study was 30MPa. Future research should explore higher-strength concrete by incorporating fibre reinforcement to enhance mechanical performance and crack resistance. 2. The influence of wood ash on concrete properties should be investigated at finer replacement intervals to better understand its impact on workability, setting time, and strength development. 3. The performance of concrete mixes incorporating wood ash and basalt powder should be assessed at temperatures exceeding 600°C to determine their suitability for extreme fire conditions. 4. To better simulate real-world wildfire exposure, the flame retardancy or fire resistance of concrete mixes should be evaluated using direct flame exposure rather than controlled heating conditions. 5. A comprehensive life cycle sustainability assessment should be conducted on concrete mixes containing wood ash and basalt powder. This analysis should evaluate their environmental impact, carbon footprint, economic feasibility, and long-term structural performance compared to conventional concrete. 115 6. Large-scale field trials should be performed to validate laboratory findings. These trials should assess constructability, curing behavior, and suitability under real-world exposure conditions. 7. Further studies should examine the long-term performance of modified concrete mixes, including shrinkage, creep behavior, and carbonation resistance, to ensure their practical applicability in structural applications. 8. A comparative study should be carried out to compare the impact of combined application of wood ash and basalt powder on concrete performance with reference to other SCMs. 9. 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Thesis/Dissertation
eng
Civil Engineering
Vancouver : University of British Columbia Library
Attribution-NonCommercial-NoDerivatives 4.0 International
Graduate
Alam, M. Shahria
Sadiq, Rehan
Behavior of low-carbon cementitious composites incorporating wood ash and basalt powder for enhanced strength and durability
Text