From composition to the microstructure and durability of limestone ternary blended cements: A systematic review

Abstract

Limestone ternary cements (LTCs) have attracted significant research and commercial attention recently, for technical and environmental reasons. Standardisation of these cements is imminent under BS EN 197-5:2021. Detailed understanding of the hydration and microstructure evolution of LTCs from different alumina-rich supplementary cementitious materials exists in the scientific literature; improved reaction kinetics and additional phase assemblages refine the pore structure. However, understanding of the performance of LTCs under exposure conditions is less prevalent. In this contribution, the available data are reviewed in a way that allows stakeholders to appreciate the capabilities of the different compositions and their performance. The focus is a critical examination of the interplay between cement composition and microstructure and its effect on durability. It is demonstrated that LTCs offer a pathway for reducing the embodied carbon dioxide of concrete without compromising their performance. Resistance to chloride ingress, sulfate attack and alkali–silica reactions are significantly improved in a manner similar to binary cements. Compared with ordinary Portland cement, carbonation and freeze–thaw resistance are generally lower, but adequate air entrainment can offer an improvement in freeze–thaw resistance. The challenge to widespread adoption of LTCs is evidence of durability under field conditions. To this end, large-scale field trialling is recommended to gain understanding of the role of combined exposures on the durability and mechanical properties of LTCs.