Towards Adoption of Composite Cements In India, produced using Slag-Limestone, Fly Ash-Limestone and Calcined Clay-Limestone Combinations

Finely ground limestone is gaining prominence for cosubstitution with conventional supplementary cementing materials (SCMs) due to synergistic interactions in composite cements containing three components, i.e., clinker-limestoneSCM. In this study, concrete performance with composite cementitious blends with fly ash-limestone, slag-limestone and calcined clay-limestone was assessed with varying levels of limestone addition. The results show that choice of SCM is more critical in governing the performance of composite cements. While calcined clay and slag can accommodate up to 20 % limestone with synergistic performance enhancement compared to 30 % binary substitution, limestone addition of 10-15 % is recommended for fly ash to ensure sufficient mechanical and durability performance. As international standards are fast moving towards the standardisation of ternary blends containing SCM like slag, fly ash and calcined clay, along with limestone filler (up to 15-20 %), composite cement standards in India should make provisions for robust ternary binders containing slag-limestone, fly ash-limestone and calcined clay-limestone to allow rapid adoption of sustainable composite cement in the Indian construction industry.