Insight into the interaction mechanism of polycarboxylate superplasticizer and polyacrylamide in cementitious materials

Abstract

Due to the economic and environmental benefits, manufactured sand is gradually replacing natural sand in concrete production. However, the residual polyacrylamide (PAM) in manufactured sand negatively affects the concrete rheology, and thus more polycarboxylate superplasticizer (PCE) is required. This study investigates the interaction mechanism between typical PAM and PCE, and further demonstrates their effect on cement hydration. Results show that there is competitive adsorption between PAM and PCE, and PAM occupies the adsorption sites of PCE on the surface of cement particles. Meanwhile, Ca2+ can combine PCE and PAM to form a polymer group, making part of PCE ineffective. Cationic PAM has the most significant effect on the adsorption of PCE on the surface of cement particles, whereas nonionic PAM has the least effect. The result of this study helps optimize the compatibility of PCE with manufactured sand concrete.