Roles and optimal dosages of monomer and initiator in toughening cement paste via in-situ polymerization

To mitigate the inherent brittleness of cement-based materials, this research introduces a novel in-situ polymerization method using acrylamide (AM) monomer and ammonium persulfate (APS) as the initiator. Mechanical testing and multi-scale analysis (SEM/FTIR/XRD) indicate that incorporating 3 % AM content improves the toughness of cement pastes by 47 % while retaining about 94 % of their initial compressive strength. This improvement arises from the formation of organic-inorganic interpenetrating networks. Early-stage performance is crucially regulated by optimized APS initiator dosage: 1 % APS guarantees full AM conversion (≤3 % AM), whereas 5 % APS accelerates PAM network formation and increases 3-day toughness by 22 % through accelerated skeletal framework development. The water released from the PAM hydrogel initially formed by AM in-situ polymerization facilitates subsequent cement hydration and promotes the reconstruction of the polymer network, which together contributes to the substantial toughening observed at later stages. The results of this study provide important insights for designing in-situ polymerized cement-based materials with greater toughness.