Polycarboxylate ether as a grinding aid for basic oxygen furnace slag and its effects in blended cements

Abstract

This research investigates polycarboxylate ether (PCE) as a grinding aid to enhance the grinding efficiency and cementitious properties of basic oxygen furnace (BOF) slag in cement applications. Ground BOF slag samples with and without PCE were systematically characterized using particle size analysis (wet and dry dispersion), Blaine fineness, BET surface area, scanning electron microscopy, FT4 powder rheometer, and surface energy by inverse gas chromatography (IGC) using a surface energy analyzer (SEA). Results indicated that a low dosage of PCE (0.05 %) significantly improved the grinding process by reducing the median particle size from 16.0 ± 0.2 μm to 13.8 ± 0.7 μm and increasing the Blaine surface area from 4149 ± 11 to 4514 ± 24 cm2/g compared to untreated ground BOF slag. This enhancement was attributed to the ability of PCE to minimize the agglomeration of particles while maintaining reasonable flow properties during grinding, even in the presence of high-energy surface sites associated with finer particles, as identified through IGC-SEA analysis. Conversely, overdosing PCE (0.5 %) led to excessive agglomeration, reflected by an increase in the agglomeration factor to 83, and together with poor powder flowability, ultimately reducing grinding efficiency. The hydration kinetics, rheological properties, and mechanical behavior of PCE-treated BOF slag-Portland Cement blends were investigated. BOF slag ground with a low dosage of PCE slightly enhanced the hydration process of the blended system, ultimately resulting in higher 28-day compressive strength (42.3 ± 0.2 MPa) compared to untreated ground BOF slag (39.3 ± 0.6 MPa). While partial replacement of cement with BOF slag positively impacted the rheological properties of the blended systems, BOF slag treated with a high dosage of PCE led to a pronounced reduction in viscosity (6.2 ± 0.1 Pa·s) and yield stress (46.2 ± 2.5 Pa) of the system. These findings demonstrate the potential of PCE as a dual-function admixture for improving both slag grinding and blended cement performance.