Effect of ultrafine limestone powder on the hydration heat and rheological properties of Portland cement paste

The effects of ultrafine limestone powder (ULP) on the early hydration heat and rheological properties of Portland cement paste were studied by measuring the hydration heat, fluidity, rheological parameters, setting time, water film thickness (WFT) and dispersion. The results show that compared with ordinary limestone powder (OLP), ULP effectively promotes cement hydration and accumulate more total hydration heat. As the hydration rate increases, the setting time of the composite paste with ULP decreases, resulting in an increased fluidity loss rate. The high specific surface area of ULP particles has a large water requirement, which reduces the WFT on the surface of particles. The reduced distance between particles leads to the increased mutual attraction and a significant increase in the plastic viscosity and yield stress of the composite paste with ULP, which is not conducive to the development of paste flowability, as evidenced by a considerable decline in the paste fluidity. The low content of ULP improves the dispersion performance of the paste. Increasing the fineness of limestone powder can improve the early hydration of composite cement paste, but it has a negative effect on the rheological properties.