Synthesis, characterization and performance of a polycarboxylate superplasticizer with amide structure

The amide-structural polycarboxylate superplasticizers (amide-PCEs) were synthesized by amidation reaction between polyacrylic acid (PAA) and amino-terminated methoxy polyethylene glycol (amino-PEG) under different conditions, and the effects of amide-PCEʹs synthesis on amidation rate and flow performance of cement paste were investigated. Fourier Transform Infrared Spectroscopy (FTIR), 1H Nuclear Magnetic Resonance (1H NMR), and molecular-weight measurements were used for structural characterization, and the results confirmed ideal amide structure and sufficient amidation reaction. Amide-PCE with the carboxyl–amino ratio of 4:1 exhibited the lowest surface tension, highest adsorption percentage, and the best paste fluidity results. Based on the above results, the dispersion and adsorption mechanisms of amide-PCE in cement–water system were discussed. The application performances in concrete showed that amide-PCE had similar slump to that of conventional PCE, but also had better air-entraining ability, bubble retention and concrete frost-resistance than those of conventional PCE. Depending on this amide structure and good performances, amide-PCE shows broad application prospects.