Different effects of NSF and PCE superplasticizer on adsorption, dynamic yield stress and thixotropy of cement pastes

Abstract

This study compares the differences and similarities of two types of superplasticizers-NSF (Naphthalene Sulfonate Formaldehyde) and PCE (PolyCarboxylate Ester)-in fresh cement paste systems, in terms of adsorption, dynamic yield stress, and thixotropic index. Results show that with either NSF or PCE addition, the more superplasticizer is added, the more it is adsorbed and the more it remains in the interstitial pore solution. The dynamic yield stress and thixotropic index also decrease with increasing addition the amount of either superplasticizer. However, NSF is less efficient in decreasing the dynamic yield stress than PCE. More importantly, the decreasing patterns of dynamic yield stress and thixotropic index are different with NSF and PCE additions; this is tied to the adsorption and dispersing mechanisms of these two types of superplasticizers.