The effects of 10% metakaolin addition on compressive strength, water absorption, shrinkage and microstructure evolution of cement paste after elevated temperatures exposure from room temperature to 800 °C were evaluated. The experimental results show that compressive strength increases at 200 °C and 400 °C compared with that obtained at ambient temperature. Up to 800 °C, compressive strength decreases rapidly. The addition of 10% metakaolin leads to the enhancement of compressive strength regardless of exposure temperatures. After thermal exposure at 400 °C, compressive strength reaches the maximum value. Thermal exposure degrades pore structure. A polynomial equation was used to indicate the shrinkage of cement paste or metakaolin-blended cement paste with testing days. Mechanical properties, permeability resistance, and shrinkage in cement pastes are closely related to the microstructure development. 10% metakaolin addition presents better thermal resistance, lower shrinkage and denser microstructure compared with pure cement paste before and after thermal exposure.
Evaluation of Properties and Microstructure of Cement Paste Blended with Metakaolin Subjected to High Temperatures