Rheological behaviour of cement pastes with low amounts of polynaphthalene sulfonate plasticizer

In this manuscript, the behaviour of cement pastes is examined when exposed to small additions of three different Polynaphthalene Sulfonate (PNS) based plasticizing admixtures. The adsorption behaviour of the polymeric molecules onto the cement particles is studied, and the minimum dosage of admixture required to achieve a significant change in the paste's yield stress is measured together with the amount of an entrapped air. Below a minimum PNS dosage, there is no significant change in the yield stress and the amount of air in the paste. Yet, beyond this minimum dosage, both the viscosity and the yield stress decrease steadily and the amount of the entrapped air increases. Interestingly, one of the PNS admixtures exhibited a slower plasticizing effect (i.e. A higher critical dosage) than two others studied PNS compounds.