Modifications in water resistance and engineering properties of β-calcium sulphate hemihydrate plaster-superplasticizer blends

Abstract

In this study, the effect of sulphonated naphthalene formaldehyde condensate (SNF) and polycarboxylate (PC) superplasticizers on the performance of β-calcium sulphate hemihydrate plaster has been discussed. A considerable improvement in the properties of β-hemihydrate plaster was observed with an increase in superplasticizer content. For 0.6 wt% SNF and PC content, a reduction of 18–20 % in water requirement is obtained and contributes 71–75 % enhancement in the compressive strength of modified pastes as compared to reference sample. The influence of superplasticizers on the hydration characteristics and morphology of the gypsum crystals have been studied using IR, SEM and Electrical Conductivity techniques. These studies indicate a significant influence of superplasticizers on the growth rates of the hydrates and leads to the formation of a dense and well compacted texture of crystals, thereby imparting high strength and better water resistance to the gypsum matrix than the reference material.