Effects of Metakaolin or Silica Fume on Hydration of Cement-Admixtures Blended Systems

摘要

This paper mainly investigated the influence of metakaolin or silica fume on the mechanical performance and hydration behaviour of cement-admixtures blended systems containing expansive admixture and superplasticizer. With metakaolin or silica fume, both compressive and flexural strength of cement-admixture blended systems increases. Restrained expansion of mortar containing metakaolin or 10% silica fume also increases, on the contrary, it decreases when mortar is incorporating 20% silica fume. Induction period shortened, the main exothermic peak and the peak of ettringite formation appeared earlier, and the heat liberating rate trended to slower when metakaolin or silica fume added into the cement-admixtures blended systems. Portlandite in the hydration product reduced when there was metakaolin or silica fume in the Systems. The formation of ettringite was promoted and the shape of ettringite turned to hexgonal pillar-liked in the cement-admixtures blended systems with metakaolin. While there was no obvious influence on the formation of ettringite in the cementitious system with silica fume, except the shape of ettringite in the hydrated cement became long pillar. Both mortar of cement-admixtures blended systems with metakaolin and silica fume seemed to be less porous, and amount and morphology of the hydrated products varies with the existing metakaolin or silica fume in cement-admixtures blended systems.