Synthesis and Performance of HPEG-AA-AMPS-HPA Polycarboxylate Superplasticizer

Abstract

An clay-resistance and slump-retaining polycarboxylate superplasticizer (PCE-RC) was synthesized using macro-monomer HPEG with different molecular weight, acrylic acid (AA), 2-acrylamide-2-methacrylic acid (AMPS) and 2-hydroxy-1-methylethyl acrylate (HPA) via H2O2-NaHSO3 redox initiator system. Effects of the acid-ether ratio, HPEG molecular weight, the amount of AMPS and HPA on the properties of PCE-RC in cement were discussed and the optimal molar ratio of HPEG3000, AA, AMPS and HPA was 1:4.5:0.1:0.1. As-synthesized polycarboxylate superplasticizer PCE-RC was characterized by GPC and FTIR. The performance of the cement paste doped with 2.0wt% montmorillonite (MMT) and concrete with cement containing MMT were tested in the presence of PCE. Results showed that cement doped with MMT performed superior fluidity and fluidity retention with the addition of PCE-RC. Compared with commercially available superplasticizer AS-KN, PCE-RC in concrete containing MMT presented better clay resistance and slump retaining performance due to the introduction of AMPS and HPA. Herein the negative charged sulfonic groups provided by AMPS could promote more PCE-RC to adsorb on MMT surface, resulting in the decrease of intercalated PCE-RC amount, which is in favor of clay resistance. While the usage of HPA monomer is beneficial for the slump-retaining ability of PCE-RC in cement due to the introduction of ester group.