Blending portland limestone cement with supplementary cementitious materials to minimize clinker content

Portland limestone cements (PLCs) have become increasingly prevalent in concrete production in the U.S. and Europe. This study evaluated cement hydration, workability and compressive strength development of blended binders for concrete produced with PLC (15 wt% limestone) and calcined clay, Class F fly ash, pumice or perlite supplementary cementitious materials (SCMs). The goal of the study was to investigate cement-SCM blends for the US market that are similar in composition to Limestone Calcined Clay Cement (LC3) binders using readily-available cements and SCMs in the U.S. Blending SCMs with PLCs changed workability, with calcined clay having a greater impact on workability than the other SCMs. Compressive strengths also were as expected for SCM blends and were somewhat lower in the PLC mortars compared to ordinary portland cement mortars. Similar carboaluminate reaction products were identified when using fly ash or a calcined kaolinitic clay, suggesting that synergies from combining cement, limestone and calcined clays are not limited to this SCM type. The use of local SCMs with PLCs is ready for implementation and allows for clinker replacement levels near that of LC3, while achieving similar performance.