Effects of compound mineral admixtures on the properties of magnesium oxysulfate cement

Adding mineral admixtures is a green, economic and effective way of improving the properties of magnesium oxysulfate cement (MOSC). Based on MOSC modified with low-calcium fly ash (L-FA), high-calcium fly ash (H-FA) and granulated blast-furnace slag (G-BS), the effects of L-FA, H-FA and G-BS and silica fume (SF) double mixing on the properties of MOSC were studied by characterising the compressive strength, water resistance, hydration heat, hydration products and micropore structure characteristics. The modification mechanism of the mineral admixtures was also investigated. The results showed that L-FA, G-BS and SF double mixing optimised the hydration product composition and the micropore structure of the MOSC, thus improving its compressive strength and water resistance. The hydration reaction rate of MOSC and 5.1.7 phase content in the hydration products was increased by H-FA and SF double mixing, but the micropore structure was not further optimised, which is why the water resistance of MOSC with H-FA and SF was not improved. The research results enrich the basic theory of mineral admixtures for improving the properties of MOSC and provide theoretical guidance for practical applications.