Cement Manufacturers Association (CMA)

45 Bespoke Chemical Additives for Marginal Grade Limestones Anant Pokharna, UNISOL CHEMTECH Limited Need for “Sweeteners” Depleting limestone deposits in India (and worldwide) are forcing cement producers to use marginal grade limestones, in turn, depending on “sweeteners” or high-grade limestones for achieving the right quality. Following flowchart demonstrates the associated challenges and constraints. Deficient Clinker Quality Low C 3 S High MgO High alkalies Poor cement quality Low compressive strengths Depleting Limestone Deposits Marginal Grade Limestone Deposits being used for cement production Low CaO content, high silica, high MgO, etc. Use of Sweeteners Addition of 5% to 25% “high grade limestone” or “sweetener” for sustaining quality of clinker and cement High Cost / Reduced Life Sweeteners sourced from distant mines increase the variable cost of cement. Sweeteners sourced from captive mines have limited life and reduce sustainability of the asset Table 1: Need for “Sweeteners” in Raw Mix