Enhancement of flexural strength of cement paste by in-situ polymerization of polyacrylamide

The incorporation of polymers in Portland cement-based materials demonstrates remarkable potential for increasing flexural strength and toughness, but faces a critical challenge of compressive strength significant reduction caused by inhomogeneous polymer distribution. To address this bottleneck, this study developed polyacrylamide-cement (PAMC) composite materials through an innovative in-situ polymerization strategy of acrylamide (AM) monomers. This study systematically investigationd the mechanical properties of PAMC with varying AM dosages (1–5%), revealing an optimal AM content achieving 89.6% enhancement in 7-d flexural strength while maintaining 91.7% retention of compressive strength. Multi-scale characterization combining FTIR spectroscopy, XRD analysis, and TG-DSC measurements elucidated the phase evolution and hydration modification mechanisms during PAMC formation. SEM observation and MIP analysis elucidated the dual mechanism involving both polymer network structure enhancement and pore structure refinement. This work establishes fundamental correlations between polymerization-controlled microstructure optimization and macroscopic performance enhancement, providing new insights for developing high-performance cement composites.