Mutual compatibility of superplasticizers (PC, SNF), grinding aids (TEA, glycol) and C3A in Portland cement systems – Hydration, rheology, physical properties and air void characteristics
Ewa Kapeluszna, Katarzyna Chrabąszcz
Abstract
The compatibility of grinding aids (TEA/glycol) and superplasticizers (PC/SNF) in low- and high-C3A cements, as well their mutual effect on the properties of pastes and fresh/hardened mortars were evaluated. The influence of various surfactant combinations on the hydration rate, flowability, compressive strength, rheology, surface tension and air void characteristics was studied. For this purpose, 6 cements based on industrial clinkers and 18 mortars were prepared under laboratory conditions. PC is more effective than SNF in low-C3A cements. In high-C3A cements, both superplasticizers have a comparable impact on consistency. Grinding aids, especially TEA, have a strong influence on the effectiveness of PC and SNF, leading to changes in the induction period, plastic viscosity and yield stress. A synergy effect of grinding aids and superplasticizers increases the air content of mortars, especially for TEA-SNF combination. Surfactants decrease surface tension, particularly PC, thus increasing the amount of air voids >300 µm.