Synthesis of early-strength steel slag grinding aids and their effect on the properties of steel slag-based cementitious materials

Abstract This study addressed the issues of low grinding efficiency, insufficient early strength of cementitious materials, and poor volume stability in steel slag processing by developing four composite grinding aids. Through optimization of the synthesis process, grinding aid d - formulated with polycarboxylate polymer combined with sodium sulfate (71%), sodium carbonate (15%), and calcium chloride (4%) - demonstrated optimal performance. Experimental results revealed that the optimal grinding duration for steel slag was 45 min, with grinding aid d increasing the proportion of 0–30 μm particles to 66.77%, grinding aids a, b and c were increased to 61.34%, 63.65% and 63.37% respectively, showing significant improvement compared to the control group. The grinding aid d enhanced the 3-day compressive strength of steel slag-based cementitious materials by 21.04%, grinding aids a, b and c were increased by 16.07%, 16.19% and 12.37%, while effectively reducing free calcium oxide content through mechanical activation to improve volume stability. Microstructural analysis indicated denser hydration product structures, increased ettringite and calcium hydroxide crystal formation, and reduced porosity in samples treated with grinding aid d. The research confirmed a positive correlation between the 0–30 μm particle proportion and hydration degree of cementitious materials, providing theoretical support for steel slag resource utilization. Steel slag-based cementitious materials can effectively reduce costs, decrease environmental pollution, and enhance the long-term strength, durability, and workability of concrete.