Strengthening cement paste via organic-inorganic network formation

The inherent brittleness of cement hydrates poses a major issue to the mechanical and durable performances of concrete. To conquer this issue, we constructed an organic–inorganic network within the cement matrix by utilizing the synergy of in situ polymerization of monomers and cement hydration, which significantly enhances its flexural strength and toughness while maintaining a comparable compressive strength with ordinary Portland cement (OPC). By tuning the proportions of acrylic acid (AA), methacrylic acid (MAA), and acrylamide (AM), the cement paste experienced an 86% increase in flexural strength with a similar compressive strength to OPC. The in situ formed organic–inorganic (polymer-cement) network provided both flexibility and stiffness, playing a pivotal role in the increased mechanical strength. Cement hydration was retarded with the incorporation of the AMA copolymer, which was supported by the offset of the maximum hydration temperature. In contrast, in situ polymerization of monomers proved more effective than directly adding polymer in improving the fluidity and mechanical strength. We hope this strategy provides a new way to increase the crack resistance of cementitious materials and thereby contributes to their overall durability.