Limestone calcined clay-based engineered cementitious composites (LC3-ECC) with recycled sand: Macro performance and micro mechanism

Limestone calcined clay cement (LC3) contributes to the development of sustainable cement-based materials. In this study, LC3 was combined with fly ash (FA) and recycled sands (RS) to develop engineered cementitious composites (ECC). Three FA/LC3 ratios (1, 1.5, and 2) and three RS particle sizes (0.15–1.18 mm, 0.15–2.36 mm, and 0.15–4.75 mm) were studied. Compared to ordinary Portland cement (OPC)-based paste, the LC3 substitution resulted in higher hydration heat and hydration degree, forming more hydration products. Although LC3 substitution produced a slightly lower compressive strength, a more robust tensile strain-hardening behavior than OPC-based ECC was achieved. The increasing FA/LC3 ratios gradually reduced compressive strength, tensile strength, and crack width. The multiple cracking behavior with controlled widths of LC3-based ECC was found to be more stable, which could be traced to the superior properties of fiber/matrix interfacial transition zone. In addition, utilizing RS as fine aggregates with various particle sizes could achieve an ultra-high tensile strain capacity exceeding 8 % for LC3-based ECC, thereby enhancing its utilization efficiency. Furthermore, the utilization of LC3 resulted in 28.6–47.1 % and 6.6–22.0 % reductions in carbon emission and embodied energy, respectively. The combination of LC3 and RS holds a promising approach to developing sustainable ECC with desirable mechanical performance. •LC3-based ECC with recycled sand exhibits a robust strain-hardening behavior.•Hydration, phase assemblage, and pore structure of LC3 paste blended with FA are studied.•Recycled sand plays a crucial role in the induction of multiple cracks for LC3-based ECC.•LC3 and recycled sand are a promising combination for sustainable ECC with desirable performance.