Influence of steel slag powders on the properties of MKPC paste

Abstract

This paper aimed to study the influence of steel slag powders on performance of magnesium potassium phosphate cement (MKPC) paste. We prepared MKPC pastes containing different contents of steel slag powders. Then their fluidity, initial setting time, compressive strength, strength residual ratio under water curing condition, shrinkage deformation and hydration temperature were measured. Furthermore, we analyzed the phase composition and micro-morphology of hardened MKPC pastes by XRD, TG-DTG, BET and SEM-EDS. The results were as follows. Adding some steel slag powders to MKPC can significantly improve the early compressive strength of hardened MKPC paste and slightly improve its late compressive strength. This should be attributed to the improvement of particle size distribution, filling and active effect of steel slag powders on MKPC paste. Compared with the 5-h, 1-day and 60-day compressive strengths of hardened MKPC paste without steel slag powders, those of hardened MKPC paste containing 20% steel slag powders were improved by 5%, 30% and 8%, respectively, and its 60-day compressive strength residual ratio under water curing condition was over 90%. In addition, adding some steel slag powders to MKPC can significantly decrease the shrinkage deformation of hardened MKPC paste, which should be attributed to improvement of pore structure and more compact structure of hardened MKPC paste. The shrinkage deformation of hardened MKPC paste containing 20% steel slag powders mainly occurred during the first 28 days of hydration. Its 28-day and 60-day shrinkage ratios were 1.7 × 10−4 and 2.34 × 10−4, respectively, and its 60-day shrinkage ratio was about 60% of that of the specimen without steel slag powders (3.97 × 10−4).