Bond Strength and Anisotropic Performance of Construction and Demolition Waste-Based Geopolymer and Cementitious Composites for 3D Additive Manufacturing

Abstract

The construction industry has immense economic, technological and environmental influence worldwide. Within this sector, conventional concrete relies heavily on Portland cement (PC) as its primary binder, leading to a surge in global PC consumption. Heightened awareness of the carbon footprint linked to cement usage has spurred substantial research into alternative binding systems like geopolymers. The recent growth in the construction sector has generated a substantial upsurge in construction and demolition waste (CDW), imposing a notable environmental burden. Besides technology and material-oriented research, operational advancements are also emerging. Notably, three-dimensional additive manufacturing (3D-AM) offers various advantages, including reduced labor costs, mold-free production and the ability to create non-standard geometric products. This thesis centers on assessing operational and material-related factors, aiming to integrate innovative, environmentally friendly construction materials derived from CDW into 3D-AM for sustainable construction. In this context, this study is planned to address a literature gap concerning anisotropy, printing time intervals, material aging and manufacturing methodologies' influence on 3D-printed structures' mechanical performance. It simultaneously conducts several tests to comprehensively evaluate the mechanical performance of printed cementitious systems under diverse conditions. Initially, the study evaluates anisotropy in samples produced at different time intervals using two different mixtures through compression tests conducted from various directions. Subsequently, it assesses bond strength changes via triplet shear and direct tensile tests on samples produced at different time intervals. Lastly, the study observes the effect of varying material ages on strength using diagonal tension and triplet shear tests. The study's findings are anticipated to make a substantial contribution to current technology by offering comprehensive insights into the impact of operational and material-related parameters on the mechanical performance of printed structures.