Open Collections

Almnini, Luay

University of British Columbia

Despite recent advances in construction digitization and concrete 3D printing, engineering a printable concrete mixture for extrudability and buildability with a minimal carbon footprint still presents technical challenges. Recent studies showed that to meet the requirements of extrudability and buildability, printable concretes are often designed with relatively smaller size aggregate and higher cement content of 3D printing concrete (3DPC) as compared to conventional concretes. The higher binder content and the relatively smaller aggregate sizes used in printable mortars make it more susceptible to thermal and shrinkage cracking. There are only a few limited studies examining the prospects of using coarse aggregates and lower cement content in printable concretes. In the current study, fly ash based lightweight aggregate (LWA) were used as a partial substitution of natural sand in varying proportions (15%,30%,50%). After conducting aggregate characterization to ensure repeatability, both fine and coarse LWAs were utilized. This study investigated both fresh and hardened properties. The flowability was checked by conducting the slump flow test and flow table test. The effect of fine and coarse LWA inclusion on extrudability was investigated by visual inspection to determine the maximum printing distance that the filament may be extruded without any fracture, blockage, segregation, and bleeding. The extrudability of the concrete mixture was determined by measuring the yield stress using the rheometer. The influence of incorporating LWA on buildability was evaluated through visual inspection, comprising layer settlement and layer deformation tests. Moreover, stress growth, viscosity recovery, and flow curve tests were conducted. The compressive strength test, flexural test, split tensile bond test were conducted on the printed concrete specimen. The findings indicated that incorporating binder material consisting of 80% fly ash and 20% cement resulted in the aggregates being classified as lightweight. This mix demonstrated satisfactory physical and mechanical properties. The fresh characteristics of 3DPC were influenced by particle size. Furthermore, it was observed that fine LWAs contributed to higher compressive strength compared to coarse LWAs, attributed to enhanced particle packing, increased density, stronger bonding, and reduced porosity. Additionally, both flexural and bond strength were influenced by LWA particle size.

Text; Still Image

2024-04-19

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/87898

Civil Engineering

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/