Effect of metakaolin waste as a pozzolanic additive on the hydration processes and properties of cement stone

Abstract

The study examines the effect of metakaolin waste, characterized by high pozzolanic activity (1451 mg/g), on the hydration processes of cement paste and the properties of cement stone. Extremely fine (average particle size 4.79 µm), characterized by a large amount of amorphous phase, metakaolin waste SEM and XRD pattern images in Figure 1 are formed at a certain stage of the technological process of foam glass granule production. Since the average particle size of metakaolin is smaller than the particle size of cement, a minimum amount of metakaolin waste (up to 10 %) was used in the studies as a cement substitute. During the study, six batches of samples were produced, in which from 0 % to 10 % of cement was replaced with metakaolin waste. After evaluating the physical and mechanical properties of cement stone, it was found that replacing 8 % of cement with metakaolin waste results in cement stone with up to 30 % higher strength and denser structure. In all samples, a temperature peak of the exothermic reaction is observed after 6-8 hours. By increasing the amount of metakaolin replaced into cement to 10 % in the composition, the temperature of the exothermic maximum reaction decreases by 8.8 %. Metakaolin waste, due to its fineness of particles and the formation of hydration products, increases the density, strength, water resistance of concrete, and improves the durability of cement stone.