Feasibility of using ultrahigh-volume limestone-calcined clay blend to develop sustainable medium-strength Engineered Cementitious Composites (ECC)

Engineered Cementitious Composites (ECC) showing multiple-cracking and strain-hardening under tension are appealing for the construction industry, but the high cement content in conventional ECC leads to high environmental impacts. Recently, the limestone and calcined clay (LCC) blend has been proposed as a promising alternative of Supplementary Cementing Materials (SCM) to address the inadequacy of common SCM such as fly ash and blast furnace slag, which have been widely-used in ECC. This paper reports a feasibility study for the first time on using ultrahigh-volume LCC blend (HVLCC, 70% and 80% by weight of binder) to produce sustainable medium-strength ECC. Three water/binder ratios (0.30, 0.35 and 0.40) and two sand/binder ratios (0.2 and 0.4) were explored. HVLCC-ECC can achieve a tensile strain capacity of 0.57–1.58%, tensile strength of 3.24–5.19 MPa and compressive strength of 33–65 MPa at 28 days. HVLCC-ECC also have sufficient early strength at 3 days (22-38 MPa), and similar fresh properties and bulk densities under surface-dry condition (1900-2100 kg/m3), as compared to conventional ECC. Additionally, HVLCC-ECC show about 1/6 higher embodied energy and about 1/6 lower embodied carbon than a typical ECC mix with 55% fly ash in the binder, and ECC with fly ash perform much better than ECC with LCC blend in terms of embodied energy and embodied carbon per unit strength or strain capacity. Nevertheless, this new version of HVLCC-ECC with adequate mechanical performance are still attractive from the perspective of shortage of fly ash in the future due to the reduced consumption of coal.