Rheological properties of cement pastes containing amine- and glycol-based grinding aids

Abstract

After the clinker grinding process, grinding aids (GAs) remain adsorbed onto cement particles, altering rheological properties and mechanical performance. The aim of this study was to assess the effect of commercially available amine-based and glycol-based GAs on variations in rheological properties including static yield stress (τ0) and viscosity (η) of cement pastes over time. Special emphasis is placed on the compliance of ground cement with ASTM C465 requirements. Compared with control mixtures, the test results showed that the addition of increased GA concentrations leads to improved flowability immediately after mixing, together with reduced τ0 and η values. This is related to a combination of factors, including the amount of water required to achieve normal consistency and the creation of repulsive forces between neighbouring cement particles. At longer elapsed times from mixing, however, the mixtures containing amine-based GA exhibited increased τ0 and η values, mostly due to chemical interactions between these molecules and the cement hydrating compounds. The efficiency of GA molecules to alter the rheological properties of cement pastes was found to be slightly affected by the increase in temperature that is normally encountered in real grinding mills.