Influence of Polyurethane-Modified Polycarboxylate on Volume Deformation of Hydraulic Concrete

This study investigated the effect of a polyurethane-modified polycarboxylate superplasticizer (P-PCE) on the volume deformation of hydraulic concrete. Macroscopically, the autogenous and drying shrinkage of concrete incorporating different types and dosages of PCEs were measured to analyze their influence. Microscopically, scanning electron microscopy (SEM) was employed to observe the hydration product morphology at 7 and 28 days. Low-field nuclear magnetic resonance (NMR) was utilized to quantify the pore structure, and a fractal dimension model was applied to correlate the microstructural characteristics with the macroscopic deformation. The results demonstrated that, compared to conventional PCEs, the laboratory-synthesized P-PCE (40% solid content) significantly reduced shrinkage and improved pore structure, thereby enhancing the volumetric stability of hydraulic concrete. The experimental results showed that, compared to ordinary PCE, P-PCE reduced the 60-day autogenous-shrinkage strain by 8.8% and the drying-shrinkage strain by 8.4%. Additionally, it decreased the total porosity by 19.46%, while also optimizing the pore structure distribution, thereby significantly improving the volume stability of hydraulic concrete.