Organic-Acid-Modified and PCE-Hybrid Grinding Aids in Slag-Blended Cements: Linking Particle Size Distribution to Hydration and Strength

Reducing clinker content while maintaining the performance of slag-blended cement requires grinding-aid strategies that improve grinding efficiency and support subsequent hydration. In this study, commercial triisopropanolamine (TIPA), diethanolisopropanolamine (DEIPA), and diethylene glycol (DEG), their organic-acid-modified derivatives, and their hybrids with a polycarboxylate ether (PCE)-based grinding aid were evaluated at 0.05% in cement systems containing two granulated blast-furnace slags (BFSs) with different physical and chemical characteristics. Particle-size distribution, X-ray diffraction, thermogravimetric analysis, scanning electron microscopy, zeta potential, PCE adsorption, and compressive strength tests were used to investigate the relationships between grinding-aid chemistry, particle characteristics, hydration, and mechanical performance. Similar Blaine fineness values did not necessarily yield comparable particle-size distributions or hydration responses, indicating that Blaine fineness alone is insufficient to assess the effectiveness of grinding aids in BFS-blended cement. Organic-acid modification was generally more effective than PCE hybridization, depending on the original grinding-aid chemistry. M-TIPA promoted the strongest hydration development and the highest 28- and 56-day strengths at all BFS replacement levels. At 30% replacement, M-TIPA mixtures with BFS 1 and BFS 2 reached 28-day strengths of 45.82 and 46.55 MPa and 56-day strengths of 52.69 and 54.13 MPa, respectively, exceeding the clinker-only control. At 45% replacement, modified alkanolamines reduced, but did not eliminate, strength loss, whereas clinker dilution dominated at 60%. Overall, grinding-aid selection should consider particle-size distribution, hydration, BFS characteristics, and replacement level, rather than relying on Blaine fineness alone, and should also account for additive chemistry and the potential influence of polymer-containing formulations on the interfacial properties of ground cement particles.