79 / 2016-11-13 15:29:04

Adsorption characteristics of polycarboxylate-based superplasticizers on the surface of tricalcium aluminate－gypsum system

The adsorption characteristics of polycarboxylate-based superplasticizers (PCs) on tricalcium aluminate－gypsum (C3A-CaSO4•2H2O) were examined by means of gel permeation chromatography (GPC) and the thermodynamic parameters of △G、△H、△S was obtained by calculation of thermodynamic equation. The Gibbs free energy of adsorption △G0ads, adsorption enthalpy △H0ads and adsorption entropy △S 0ads were linear regression. Results clearly showed that the Gibbs free energy of the system is negative, which indicated that the adsorption behavior is a spontaneous process. As the temperature increased, the adsorption amounts of PCs on surface of C3A-CaSO4•2H2O increased. The adsorption thermodynamics parameters is =-18.714kJ•mol-1， /=0.072kJ•mol-1•K-1， =-39.715 kJ•mol-1 (20℃). This work can be provided theoretical guidance for the application of PCs in cement and concrete.