Novel use of waste calcined clay brick powder in sustainable ultra-high ductility strain-hardening geopolymer composites: Micro-characteristics and mechanical behavior

Strain-hardening geopolymer composites (SHGC) exhibit low-carbon characteristics and excellent mechanical performance, but the conventional precursors used in SHGC preparation are limited in supply and expensive. Using recycled brick powder (RBP) ground from calcined clay brick waste as a green precursor for fabricating ultra-high ductility SHGC promotes the high-value utilization of calcined clay brick waste while decreasing the reliance on conventional mineral precursors such as fly ash (FA) and slag. This investigation systematically studied the microstructural characteristics and mechanical performance of RBP-SHGC. Incorporating RBP as a moderate substitute for FA and slag had negligible influence on the microstructure and geopolymeric products of SHGC, but substituting RBP for high-dosage slag negatively affected the microstructure. The mechanical strength initially rose and then decreased with the increasing substitution ratios of RBP for FA and slag, though RBP-blended SHGC maintained considerable strength even at 100% replacement rates. Substituting RBP for an appropriate proportion of FA and slag improved both the uniaxial tensile strength and strain capacity. The SHGC in which RBP simultaneously replaced 50% of FA and 50% of slag exhibited an ultimate tensile strain comparable to that of the reference SHGC. Raising the alkali-activator modulus and alkali content effectively improved the microstructure and mechanical behavior of RBP-blended SHGC.