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Abstract

Underground concrete infrastructure used to transport wastewater is deteriorating faster than its expected design life in many parts of the world due to microbial-induced concrete corrosion (MICC). This accelerated degradation is costing governments and municipalities billions of dollars in repairs, in addition to the significant environmental consequences associated with repairing or replacing damaged structures. Current industry solutions fail to provide long-term durability, are difficult to implement, and often release toxic chemicals into the environment. Additionally, these solutions typically have a high embodied carbon, raising critical sustainability concerns. Geopolymers (GP), in contrast, offer a promising alternative due to their improved sustainability, reduced toxicity, and enhanced performance compared to traditional rehabilitation techniques. This thesis details development of a novel sprayable geopolymer to apply as a repair material to deteriorated wastewater infrastructure. The work also investigates this goal by exploring performance of the novel geopolymers in field conditions to gain an understanding of how mixes can be optimised for Microbial Induced Corrosion (MIC) resilience, which has only been completed to a rudimentary degree prior to this study. Additives including heavy metals, and fibres alongside variations in calcium content are explored to understand what factors impact GP performance. Assessment is completed with physical, mechanical, and chemical analysis to provide holistic conclusions on GP performance. This is complimented with a rheological study, to facilitate the sprayability of geopolymer mixes. Sprayability is vital to allow practical application of such a material, however, exploration of sprayed geopolymers has been limited until this point. The results of these studies are combined to present an optimised mix of MIC resilient GP that can be sprayed to meet the original goal of the study: to develop a sustainable material that can be adopted by industry to repair existing underground infrastructure.