Hydration and Strength Development in Limestone Calcined Clay Cements with Low-Grade Limestone

Limestone calcined clay cement (LC3) is a sustainable alternative to ordinary Portland cement. It helps to achieve a clinker factor as low as 0.5. Cement-grade limestone with a CaCO3 content above 75% is usually used to manufacture LC3 cement. Sometimes limestone contains impurities like silica, clay, dolomite, etc., beyond the specified limits recommended for cement manufacture. This limestone is commonly known as low-grade limestone. This paper discusses the results of a study on the feasibility of utilising low-grade limestone in LC3 cement. Isothermal calorimetry was done to understand the hydration kinetics of the cementitious systems. Compressive strength measurements on mortar cubes were done to understand how strength is affected due to the presence of impurity in limestone. Results indicate that LC3 systems with low-grade limestone give either comparable strength or higher strength in compression, compared to the control specimens of ordinary Portland cement. Calorimetry results also showed an acceleration in early hydration for the blends with low-grade limestone. In short, low-grade limestone is a promising alternative to pure limestone in LC3 systems.