The Reactivity Enhancement of Steel Slag Using Different Organic Activators and Its Effects on the Cement Properties: A Comparative Study

Steel slag has the potential to be used as a kind of cement admixture, but its low reactivity, weak soundness, and poor grindability limit its widespread use. Compared with traditional activation approaches, chemical activation demonstrates greater effectiveness; however, conventional chemical activators are often associated with high dosage demands and considerable cost. To address these drawbacks, this study focused on identifying more sustainable and efficient activators. It conducted a systematic investigation and comparison to evaluate the effects of four organic activators—triethanolamine (TEA), triisopropanolamine (TIPA), ethylene glycol (EG), and glycerol (GLY)—on the performance of steel slag–cement composite binders. The results indicated that each activator accelerated the hydration of steel slag and enhanced its activity. At a dosage of 0.03%, TEA demonstrated the most pronounced enhancement, increasing the 7- and 28-day activity indices from 67% and 78% to 83% and 92%, respectively. At a dosage of 0.02%, TIPA, EG, and GLY achieved 28-day activity indices exceeding 86%. Furthermore, all activators improved the flowability of the mortar. At a dosage of 0.04%, TEA improved flowability by 7.4% and exhibited good compatibility with the superplasticizer. Similarly, EG showed significant improvements in both flowability and superplasticizer compatibility. Therefore, based on the overall enhancement of the activity index, the performance of the activators could be ranked as follows: TEA > TIPA > EG > GLY . From an economic standpoint, a 0.03% dosage of TEA significantly enhanced both activity and flowability, while also reducing the superplasticizer dosage needed to achieve equivalent workability, demonstrating its promising application potential.