Performances and working mechanism of a novel polycarboxylate superplasticizer synthesized through changing molecular topological structure.

A novel star-shaped polycarboxylate superplasticizer (SPCE) was synthesized through a simple two-step method. 1H Nuclear Magnetic Resonance (1H NMR) and Infrared Spectroscopy (IR) measurements were used for structural characterization. SPCE and comb-shaped polycarboxylate superplasticizer (CPCE) with same molecular weights were designed and synthesized. The cement paste containing SPCE exhibited better fluidity, fluidity retention, water reduction, 25% lower saturated dosage of PCE, 10% longer setting time, lower hydration heat, more delayed hydration heat evolution and lower amount of hydration products at early ages. Furthermore, the adsorption behavior of SPCE and CPCE in cement pastes and the zeta potential were investigated, and then the working mechanism of SPCE was theoretically explained. It is interesting that changing topological structure from comb-shape to star-shape can achieve the optimization of dispersion effect, and further improve the working effectiveness. The aims of this study are to provide a new avenue to synthesize superplasticizer with novel structure achieving the chemical diversity of superplasticizer structure, and to verify the contribution of optimizing molecular shape. This new type of superplasticizer can be used as a rheology modifying agent in fresh cement-based materials.