The low flexural strength and high brittleness of cementitious materials impair their service life in building structures. In this study, we developed a new polymer-modified mortar by in situ polymerization of acrylamide (AM) monomers during the cement setting, which enhanced the flexural and durable performances of mortars. The mechanical properties, micro-and-pore structures, hydrated products, interactions between cement hydrates and polyacrylamide (PAM), and durability-related properties of the mortars were investigated comprehensively. Mortars with 5% PAM exhibited the best performance in terms of flexural strength among all the mixtures. The mechanical strength of cement pastes modified by in situ polymerization of AM monomers was significantly superior to those modified by PAM. The chemical interactions between the polymer molecules and cement hydrates together with the formation of polymer films glued the cement hydrates and polymers and resulted in an interpenetrating network structure, which strengthened the flexural strength. Reductions in porosity and calcium hydroxide content and improvement in capillary water absorption were achieved with the addition of PAM. Finally, the chloride resistance was significantly enhanced with the incorporation of PAM.

胶结材料的低弯曲强度和高脆性损害了它们在建筑结构中的使用寿命。在这项研究中，我们开发了一种新型的聚合物改性砂浆，它在水泥固化过程中通过丙烯酰胺（AM）单体进行原位聚合，从而提高了砂浆的抗弯性能和耐久性。全面研究了砂浆的力学性能，微孔结构，水合产物，水泥水合物与聚丙烯酰胺（PAM）之间的相互作用以及与耐久性相关的性能。就所有混合物而言，PAM含量为5％的砂浆表现出最佳的抗弯性能。原位改性水泥浆的机械强度AM单体的聚合显着优于PAM改性的那些。聚合物分子与水泥水合物之间的化学相互作用以及聚合物膜的形成将水泥水合物和聚合物胶粘在一起，形成互穿的网络结构，从而增强了挠曲强度。通过添加PAM，可以降低孔隙率和氢氧化钙含量，并改善毛细管吸水率。最后，加入PAM可以显着提高耐氯化物性。