Micromechanical analysis of polyacrylamide-modified concrete for improving strengths

This paper studies how polyacrylamide (PAM) alters the physicochemical and mechanical properties of concrete. The microstructure of PAM-modified concrete and the physicochemical reaction between PAM and concrete were studied through scanning electron microscope (SEM), differential thermal analysis (DTA), thermal gravimetric analysis (TGA), and infrared spectrum analysis. Meanwhile, the workability and strengths of cement paste and concrete were tested. PAM's modification mechanism was also discussed. Results indicate that PAM reacts with the Ca2+ and Al3+ cations produced by concrete hydration to form the ionic compounds and reduce the crystallization of Ca(OH)2, acting as a flexible filler and reinforcement in the porosity of concrete and, therefore, improving concrete's engineering properties. PAM also significantly alters the microstructure at the aggregate–cement interfacial transition zone. Mechanical testing results indicate that the fluidity of cement paste decreases initially, then increases, and decreases again with increasing PAM content. PAM can effectively improve the flexural strength, bonding strength, dynamic impact resistance, and fatigue life of concrete, though it reduces the compressive strength to some extent.