0000000001011458
AUTHOR
Marc Domenech
Hydration of calcium sulfate hemihydrate (CaSO4·H2O) into gypsum (CaSO4·2H2O). The influence of the sodium poly(acrylate)/surface interaction and molecular weight
Abstract The retarding influence of sodium poly(acrylate) (PANa) on the hydration of calcium sulfate hemihydrate (CaSO 4 · 1 2 H 2 O) was investigated. This study reports the influence of sodium poly(acrylate) on hemihydrate dissolution, on homogenous and heterogeneous gypsum (CaSO 4 ·2H 2 O) nucleation as well as on gypsum growth. It is shown that adsorption of PANa does not hinder the dissolution of hemihydrate in the present experimental conditions. The specific interaction of PANa with gypsum can explain the oriented growth of gypsum crystal. The gypsum growth is slowed down but cannot be blocked by the adsorption of PANa. On the other hand, PANa can block the heterogeneous and homogeno…
Correlating surface forces with surface reactivity of gypsum crystals by atomic force microscopy. Comparison with rheological properties of plaster
Abstract Atomic Force Microscopy (AFM) was used to image the surface reactivity as well as to characterize quantitatively the surface forces between two gypsum (CaSO 4 , 2H 2 O) crystals. Measurements on different crystal faces, which vary in morphology, structure, hydrophilicity, surface charge, were performed in both air and ionic solutions. In ionic solutions, varying the experimental parameters, the ionic nature and the concentration as well as the duration of the contact leads to the conclusion that the adhesion occurs whatever the orientation of faces. Nevertheless, the magnitude of the adhesion of a physical nature (Van der Waals and ionic correlation) depends on the surface charge d…