Study on the modification mechanism and properties of aluminate cement via acrylamide in-situ polymerization and polyacrylamide direct incorporation

Aluminate cement (CAC) has been extensively applied in emergency repair projects due to its rapid hardening, early strength and resistance to corrosion. However, in specific application scenarios, such as when subjected to dynamic or flexural loads, its inherent brittleness may lead to insufficient flexural strength, thereby limiting its application. To address this problem, this paper investigates the modification of CAC via in-situ polymerization with different dosages of acrylamide (AM) and the direct incorporation of different dosages of polyacrylamide (PAM). The study systematically explores the effects of AM and PAM on paste performance, mechanical properties, and microstructure, as well as the mechanisms underlying the different modification modes. The results demonstrated that the PAM generated by AM in-situ polymerization modification formed a more continuous organic-inorganic interpenetrating double-network structure with stronger interfacial bonding with the hydration products of CAC, which significantly enhances the mechanical properties and toughness of CAC. When the AM dosage level was 20%, the flexural strength, axial compressive strength and relative toughness of the samples reached 24.20 MPa, 25.29 MPa and 127.44 respectively at 28 d. While the direct addition of PAM reduced the mechanical properties of CAC, and the 28 d flexural strength and axial compressive strength were reduced to 2.10 MPa and 1.59 MPa respectively, when the dosage of PAM was 5%. The poor dispersion and continuity of PAM in the CAC paste, and the weak combination with the hydration products of CAC, limit its toughening effect. The best effect is achieved when the dosage is 5%, and the relative toughness index can reach up to 2.31. In summary, the toughening and strengthening effect of AM in-situ polymerization modification on CAC is significantly superior to that of direct PAM addition.