Influence of nickel slag powders on properties of magnesium potassium phosphate cement paste

Abstract

This paper aims to study the effect of nickel slag powders on the properties of potassium magnesium phosphate cement (MKPC) paste. MKPC pastes containing different contents of nickel slag powders were prepared. We then tested their fluidity, setting time, compressive strength, the residual ratio of compressive strength under water curing condition, shrinkage deformation and hydration temperature. The micro morphology and the phase compositions of hardened MKPC pastes were also analyzed. The results indicate that adding some nickel slag powders in MKPC can improve the particle gradation of alkali components in MKPC and further improve the fluidity of fresh MKPC paste. The water stability of MKPC paste can be improved obviously by adding 30–40% nickel slag powders. The 60-day compressive strength of MKPC paste with 30–40% nickel slag powers exceeds 70 MPa and the residual ratio of compressive strength under water curing condition is higher than 100%. This should be attributed to the decrease in the proportion of harmful pores in hardened MKPC paste with some nickel slag powers. In addition, adding some nickel slag powders can obviously reduce the shrinkage deformation of MKPC paste. The 60-day drying shrinkage rate of hardened MKPC paste with 30% nickel slag powders is only 48.2% of that of the reference sample without nickel slag powders. This is attributed to the improvement of particle size distribution of alkali components, the micro-aggregate effect of nickel slag powders and less water use. These factors result in the decrease in the total porosity of the hardened MKPC paste with nickel slag powders and finally smaller shrinkage deformation.