Effect of Metakaolin on the Water Resistance of Magnesium Phosphate Cement Mortar

Abstract

In order to study the effect of metakaolin on the water resistance of magnesium phosphate cement mortar, we took four factors as research objects: the setting time, fluidity, compressive strength, and water resistance of magnesium phosphate cement mortar. These were studied after adding equal gradations of metakaolin, and we then carried out SEM microcosmic experiments on the best group. The results showed that with the increase in metakaolin content, the setting time of magnesium phosphate cement decreased gradually, and the fluidity of the mortar decreased as a whole. The effect of metakaolin on the fluidity of the magnesium phosphate cement mortar was not significant when the content of metakaolin was less than 8%. Metakaolin was able to improve the pore structure of magnesium phosphate cement mortar; for example, it improved its compressive strength and water resistance due to both chemical and physical interactions. The water resistance of mortar samples in the same timeframe increased first and then decreased with the increase in metakaolin content. When the content of metakaolin was 12%, the water resistance of magnesium phosphate cement mortar achieved the optimal results. A 50.32% improvement of the 56 d strength retention rate and a 54.89% improvement of the 90 d strength retention rate proves its effective long-term water resistance.