Comparison of ester-based slow-release polycarboxylate superplasticizers with their polycarboxylate counterparts

Ester-based slow-release polycarboxylate superplasticizers (PCT) exhibit high fluidity and a good slump retention effect on concrete slurries. Hence, in this study, a previously prepared unsaturated triethyl citrate (as the functional monomer) and acrylic acid and isoprenyloxy polyethylene glycol (as the primary raw materials) were employed to synthesize a series of PCT via free-radical polymerization. Proton nuclear magnetic resonance and Fourier-transform infrared spectroscopies were employed to characterize the PCT. Additionally, the fluidity, adsorption performance, and zeta-potential (zeta-potential) tests of the cement paste revealed that the polymers exhibited a good dispersion effect and excellent retention of fluid, e.g., PCT-2 reached up to 305 from 265 mm in 3 h. The hydration heat and scanning electron microscopy results revealed that the PCT exhibited much stronger retardation of cement hydration than did traditional polycarboxylate superplasticizers probably because of its incomparable dispersion and sustained-release properties. After 1, 7, and 28 days of hydration, the microstructure of the cement paste became denser, favoring the strengthening of the cement mortar.