Abstract: In order to expand the application of steel slag in different cementitious materials, the effects of single addition of steel slag and dual addition of steel slag and fly ash on the flowability, heat of hydration, compressive strength, and water resistance of magnesium oxychloride (MOC) cements were investigated. Microscopic methods such as X-ray diffraction (XRD), low-field nuclear magnetic resonance (LF-NMR) and scanning electron microscopy (SEM) were used to characterize the hydration products and microscopic morphology.The results showed that theaddition of steel slag as supplementary cementitious materials to MOC can improve the working performance of MOC. When the dosage of steel slag is 10%, the effect on the compressive strength of MOC at all ages is not obvious, and the water resistance of MOC is improved. The compressive strength and water resistance of MOC decrease significantly when the dosage is greater than 10%. There is a hydration superposition effect of steel slag and fly ash in MOC, and when the dual addition ratio is 1∶1, the specimen has the highest total hydration exotherm, the best water resistance, and the softening coefficient is increased by 0.38.

Key words: steel slag, magnesium oxychloride cement, fly ash, water resistance, pore characteristics