Synthesis of a novel polycarboxylate superplasticizer with carboxyl group as side chain terminal group to enhance its clay tolerance

The dispersion ability of polycarboxylate superplasticizer (PCE) in fresh concrete was much impeded by clay impurities. To improve the dispersion of PCE in the clay-contained concrete, a novel PCE with carboxyl as a specific branched chain terminal group was synthesized, using modified polyether as the raw material which was prepared through esterification between hexahydrophthalic anhydride (HHPA) and isobutenyl polyoxyethylene ether (IPEG) with hydroxy as the terminal group. The esterification product and PCE molecular structure were characterized by infrared spectroscopy and 1HNMR resonance. The results confirmed that the product molecular structure was a comb-type copolymer with long-chain terminal carboxyl group and PEO attached directly to the backbone chain. The as-synthesized PCEs had favorable dispersibility in cement than conventional PCE in the presence of montmorillonite (Mmt) clay. This can be attributed to the introduction of electronegative carboxyl to PCE long-chain terminal group, which reduces the adsorption of PCE on Mmt, and thus improves the tolerance of PCE to the Mmt.