Influence of Calcined Clay-Limestone Ratio on Properties of Concrete with Limestone Calcined Clay Cement (LC3)

In this study, the compositional robustness of limestone-calcined clay combination as clinker replacement in cement, and its effect on concrete performance was assessed in detail. The ratio of limestone-calcined clay in the LC3 with 55% clinker was varied from 1:1.25, 1:2 and 1:3.5 with increasing limestone dosage from 10 to 20%. Additionally, binary binders with calcined clay at 30% (CC30) and 42% (CC42) replacement were studied for benchmarking and dissociating limestone’s contribution to the performance of LC3 binder. Concretes were prepared with 360 kg/m³ and 0.45 with fly ash-limestone and calcined clay-limestone combinations. Early hydration benefits from limestone ensured that binders with a combination of limestone-calcined clay showed higher compressive strength than the binary substitution of 45% calcined clay binder up to 180 days. The higher reactivity of calcined clays resulted in a tremendous rise in resistivity for all calcined clay binders by early curing duration, i.e. 7 days. Resistivity development confirmed the synergistic impact of limestone-calcined clay combination, which reaffirms the potential ability of the calcined clay to complement the utilization of higher amount of less energy-intensive limestone in the cementitious materials. Additionally, the influence of varying limestone-calcined clay ratio on time-dependent change in chloride resistance by migration test was probed, and the impact of chloride build-up at the steel surface during service life is also discussed.