Evaluating Durability: A Comparative Study on the Influence of Fly Ash and Silica Fume in Potassium Magnesium Phosphate Cement Mortar

The compressive strength retention rates of ordinary, 10wt% fly ash (FA) modified, and 15wt% silica fume (SF) modified potassium magnesium phosphate cement (MKPC) mortar blocks at different ages were measured, under the curing of water, 5%NaCl solution, and 5%Na2SO4 solution. This was used to investigate their water resistance and salt resistance abilities. The freeze-thaw cycle deterioration was further compared and analyzed. Finally, scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to investigate the hydration products. The results indicated that the compressive strength retention rate of the SF-modified MKPC mortar was 82.7% when it was cured in water for 150 days and above 85% when in the two mentioned salt solutions for 150 days. Compared to FA, the water resistance, salt erosion resistance, and freeze-thaw resistance of MKPC mortar were all improved by the SF because of its good physical filling and chemical effect.