Organic acid-modified grinding admixtures: effects on grinding efficiency, hydration kinetics, and early-age...

In this study, the performance of grinding aids (GAs) was enhanced through the organic acid modification of commercially used triisopropanolamine (TIPA), diisopropanolamine (DEIPA), and diethylene glycol (DEG)-based additives using acetic, propanoic, and hexanoic acids. Cements produced with the modified and commercial grinding aids at a dosage of 0.05% were systematically evaluated for particle size distribution, hydration kinetics (calorimetry, XRD, and TGA), microstructural development (SEM), setting time, and early-age compressive strength. The results demonstrated that organic acid modification markedly improved grinding efficiency. Among the modified additives, hexanoic-acid-modified TIPA (M-TIPA-2) exhibited the most pronounced effect, producing a significantly finer cement with an increased fine particle fraction. Hydration analyses demonstrated that M TIPA 2 significantly accelerated both C₃S consumption and calcium hydroxide (CH) formation, reaching a 40% replacement level compared to the reference cement. This enhancement in hydration kinetics was accompanied by the development of a denser, more homogeneous microstructure, as confirmed by SEM observations. All grinding aids reduced setting times, with the greatest reductions observed with TIPA-based modifications (22-26% compared to reference). Furthermore, the modification process mitigated the early-age strength reductions associated with commercial TIPA and DEIPA and enhanced the strength performance of DEG-based systems. Overall, the findings demonstrate that organic acid modification extends the role of grinding aids beyond physical comminution, enabling them to act as chemical modulators of cement hydration. In this context, hexanoic-acid-modified TIPA emerged as a highly effective additive, offering a synergistic combination of enhanced grinding efficiency, accelerated hydration, and improved early-age cement performance.