Mechanistic understanding of strength and microstructural evolution of in-situ polymerization modified cement pastes

In-situ polymerization has garnered significant attention due to its remarkable ability to enhance the toughness of cement-based materials. Beyond exploring the beneficial effects of in-situ polymerization, understanding how strength evolves in modified materials is essential for practical applications. In this study, we investigate the strength evolution of in-situ polymerization-modified cement pastes from the fresh state to later ages, elucidating the underlying mechanisms through analyses of heat release, hydration products, and microstructural changes. Experimental results reveal that in-situ polymerization with monomer contents of 1 %, 3 %, and 5 % enhances the flexural strength at 56d by 4.34 %, 42.89 %, and 81.03 %, respectively, compared to plain cement pastes. Strength evolution from fresh state to later age further reveals a four-stage development process in polymer modified cement that differs from conventional cement hydration. These stages are driven sequentially by monomer adsorption, polymerization, cement hydration, and prolonged late-age hydration. These insights provide critical guidance for optimizing casting and demolding processes while expanding applications in 3D printing and rapid repair materials.