Hydration Characteristics and Mechanic Properties of Basic Magnesium Sulfate Cement Containing Steel Slag

The hydration characteristics and mechanical properties of basic magnesium sulfate (BMS) cement containing steel slag (SS) are studied in the work. The heat release of the composite binders during hydration process was monitored, the phase compositions of hydration products were analyzed, the microstructures of hardened pastes were investigated, moreover, the compressive strength was tested. The results show that the hydration exothermic rate of BMS is slowed and the cumulative heat of BMS is suppressed by SS addition. The incorporation of SS leads to the formation of C-S-H, CaSO4•2H2O and Mg(OH)2, and suppresses the formation of 5-1-7 phase. Compared to plain BMS, the pore structure of the composite paste with SS addition is much coarser, the crystallization and growth of Mg(OH)2 lead to the occurrence of microcrack and large pores of the paste. The mechanical property of BMS is decreased by SS addition, especially when the content of SS addition reaches 20%, the compressive strength is significantly weakened in all tested ages.