Abstract: The absorption equilibrium of polycarboxylate-type superplasticizer ( PCE ) on montmorillonite ( MMT ) and its influencing factors were investigated by the gel permeation chromatography ( GPC ) method. The results show that montmorillonite had strong adsorption for PCE and its adsorption amount increased with concentration. The adsorption amount was 7. 03 mg·g-1 as the concentration of PCE was 2. 00 g·L-1(PCE standard dosage in the concrete),While the concentration of PCE was double of the above, the adsorption amount was 14. 61 mg · g-1;The maximum adsorption capacity of PCE on montmorillonite (saturated adsorption amount) was about 21. 18 mg·g-1. The change of the pH value has little impact on adsorption quantity when the concentration of PCE was lower than 2. 50 g·L-1 . But the presence of Ca2+, Mg2+metal ions could increase the adsorptionamount of PCE among which Mg2+ion was particularly evident. Further studies had shown that adsorption of PCE on montmorillonite was an endothermic process and adsorption process conforms to the secondary dynamics equation. The adsorption could reach equilibriumjust in 5-10 min.

Key words: polycarboxylate-type superplasticizer;montmorillonite;adsorption equilibrium;adsorption kinetics;gel permeation chromatography method