EFFECTS OF COMBINATIONS OF LIMESTONE POWDER AND METAKAOLIN ON MORTAR COMPRESSIVE STRENGTH DEVELOPMENT

Cement production is a major contributor to carbon dioxide (CO2) emissions, and concrete is one of the most widely used building materials in the world. To reduce CO2 emissions from cement, supplementary cementing materials have been widely introduced in mortar and concrete mixtures. This research will explore the mechanism that determines the development of compressive strength in mortar made with partly substituted cement and a mixture of limestone powder and laboratory-quenching heat-treated kaolinite clay (also called metakaolin). Metakaolin is rich in Southeast Asian countries and needs further investigation to adopt in cement systems. Limestone powder and metakaolin constitute 45% of the binding cement ingredient by weight (dry). The strength was evaluated using mortar, and the microstructure was determined using paste. The results show that at 28 days, the compressive strength of mortar containing 45% cement substitution by 15% limestone powder and 30% metakaolin with 1% PCE (per B45S 1:2) was 97% relative to the reference mortar. However, due to the impurities in metakaolin, its synergistic interaction is limited, which results in the compressive strength being lower than anticipated.