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 △G0 ads, adsorption enthalpy △H0 ads and adsorption entropy △S 0 ads 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 Had =-18.714kJ·mol-1 ， ad S /=0.072kJ·mol-1·K-1， θ G ad =-39.715 kJ·mol-1 (20℃). This work can be provided theoretical guidance for the application of PCs in cement and concrete.

[1] Ran Q, Somasundaran P, Miao C, et al .Effect of the length of the side chains of comb-like copolymer dispersants on dispersion and rheological properties of concentrated cement suspensions [J]. Journal of Colloid and Interface Science, 2009, 336(2): 624～633.

[2]Wu Huaming, Xue Yonghong, Lin Zongliang, et al. The temperature dependence of the polycarboxylic superplasticizer[J]. China Concrete and Cement Products, 2011, 186(10): 9～12.

[3] Yamada K, Takahashi T, Hanehara S, et al .Effects of the chemical structure on the properties of polycarboxylate-type superplasticizer[J]. Cement and Concrete Research, 2000, 30(2):197～207.

[4] Liu Ming, Lei Jiaheng, Fu Chengfei, et al .Synthesis, Properties and Dispersion Mechanism of Sulphonated Acetone-Formaldehyde Superplasticizer in Cementitious System[J]. Journal of Wuhan University of Technology-Mater. Sci. Ed. 2013, 28(6): 1167～1171.

[5] Liu Ming, Lei Jiaheng, Guo Liping,et al. The application of thermal analysis, XRD and SEM to study the hydration behavior of tricalcium silicate in the presence of a polycarboxylate superplasticizer. Thermochimica Acta. 2015, 613: 54～60.