Autogenous self-healing of construction and demolition waste-based Engineered Geopolymer Composites: Mechanical property characterization

This study investigates the autogenous self-healing performance of CDW-based Engineered Geopolymer Composites (EGC), focusing on flexural properties. Key components of CDW, roof tile (RT), hollow brick (HB), red clay brick (RCB), concrete (C), and glass (G), were used as precursors in mixed form and were incorporated with slag in some mixtures. Different combinations of NaOH, Na2SiO3, Ca(OH)2 were used as alkali activators. Untreated fine recycled concrete aggregates (FRCA) with maximum grain size of 2 mm were used to make EGC matrices fully CDW-based. Reinforcement was provided by hybrid polyethylene (PE) and nylon (N) fibers at 2 % volume. Mechanical characterization was made through flexural strength, splitting tensile strength, deflectionhardening, toughness, and stiffness parameters on healed and unhealed specimens. Self-healing development was examined under a microscope, and SEM/EDS and XRD analyses were performed to characterize the selfhealing products. Despite the presence of significantly larger FRCA, deflection-hardening accompanied by multiple microcracking was achieved for all mixtures. Microcracks with widths of up to nearly half a millimeter (460 mu m) were healable via the formation of aluminosilicate phases, Na2CO3, and CaCO3, achieving a significantly higher healing capacity compared to traditional cementitious systems. Mixtures with fully CDW-based matrices demonstrated better crack healing than slag-substituted counterparts, likely due to enhanced ongoing geopolymerization. NaOH + Na2SiO3 activator combination was essential for healing efficiency. Self-healing markedly improved flexural strength, deflection-hardening, and toughness, highlighting its significance for promoting sustainable and resilient construction practices.