Enhanced slump retention using polycarboxylate superplasticizers obtained by micro-crosslinking reaction

Abstract

In this paper, a facile method was adopted to synthesize polycarboxylate (PC) superplasticizers which rendered excellent initial fluidity and workability of mortar in 1 hour. Micro-crosslinking was introduced in the PC molecules and the ester groups in crosslinker can form carboxyl groups in the hydration solution of cement. The micro-crosslinked PC (MPC) superplasticizer was synthesized from butenyl alkylenepolyoxyethylene-polyoxypropylene ether, sodium methacrylate, acrylic acid with trimethylolpropane triacrylate (TMPTA) as the crosslinker in water medium. The effect of monomer content and the dosage of crosslinker on the performance of MPC were studied. Fourier transform infrared spectroscopy and dynamic light scattering analyses were conducted to characterize the molecular structure of MPC. The fluidity of mortar in 1 hour was tested to study the fluidity and the retention in fluidity of mortar with the presence of MPC, indicating that micro-crosslinking with trifunctional crosslinker TMPTA was an effective way to improve the fluidity retention without sacrificing the initial fluidity. Investigations on early hydration of cement with MPCs were performed using XRD and TGA. Results showed that the addition of MPCs can slightly improve the degree of early hydration.