Effects of Submicron Metakaolin on Hydration and Compressive Strength of Portland Cement Slurry

Submicron metakaolin (SMK) is an ultrafine aluminosilicate material, which was used for improving properties of cement slurry in this paper. SMK was added to the slurry mix as a partial substitute for Portland cement in proportions of 1%, 3%, 5% and 7%. To explore the influence of SMK on hydration of cement slurry, the heat flow and pH measurement was used to indicate that SMK significantly increased the rate of heat release and total heat release, increase the rate of calcium hydroxide (CH) generation in the pore solution at initial stage of hydration. The hardened specimens at different ages (3-28 days) were measured by X-ray diffraction, Differential Thermal Analysis and Compressive strength. The results showed that: SMK displayed pozzolanic effect which reduced CH content and increased the generation of Calcium Silicate Hydrate (C-S-H) gel at later stages of hydration. The compressive strength tests showed that SMK highest increased compressive strength of the slurry by 67% and 19% at 3d and 28d over plain cement slurry. It was concluded that SMK could improve many properties of cement slurry and has the use potential on actual projects.

Automated summary

Submicron metakaolin (SMK) as a partial substitute for Portland cement can significantly increase the heat release rate and total heat release of cement slurry, reduce the content of calcium hydroxide (CH) and increase the generation of Calcium Silicate Hydrate (C-S-H) gel, thus improving the compressive strength of the slurry.