Performance improvement of magnesium oxysulfate cement by the combination of additives

Abstract

Magnesium oxysulfate cement (MOS) is a lightweight and low-alkalinity inorganic cementitious material that has been widely used in the construction field. However, MOS required a longer setting time in certain conditions, which had received less research attention. This article explores the influence of various single and composite additives on the setting time and water resistance of MOS composite materials. Additionally, it delves into how the composition of active groups within these additives and fluctuations in pH levels during the hydration process impact the performance of MOS. The findings showed that composite additives significantly prolonged the initial setting time of MOS and improved the early compressive strength and water resistance. The combination of citric acid (CA) and sodium tripolyphosphate (SHPP) exhibited the best modification effect. After modification, the initial setting time increased by 215.4 % compared with pure MOS, and the compressive strength increased by 112.8 % after curing for 28 days. The setting time and mechanical strength of MOS composites could be regulated by adjusting the pH during hydration and its chelating effect on Mg2+, providing theoretical support for the broad application of MOS composites.