pH stimuli-responsive poly(acrylamide-co-sodium alginate) hydrogels prepared by γ-radiation for improved compressive strength of concrete

Cross-linking of superabsorbent hydrogels based on poly(acrylamide-co-sodium alginate) is carried out using Co-60 gamma-radiation. Hydrogels of PAM/NaAlg with 1.5:0.5 and 1.0:1.0 w/v concentrations showed good gel contents of 87 and 66 (%) and swelling degrees in water of 3.7 and 5 (g/g) after 40 min, respectively. The chemical structure of the hydrogel is confirmed by FTIR, XRD, and ESR. The morphology of the hydrogel is observed using scanning electron microscopy. Intramolecular H-bonding in the hydrogel network is confirmed by TGA and DSC. The pH-responsive swelling behavior of (PAM-co-NaAlg) hydrogels is tested in different pH ranges showing higher swelling capacities in basic than in acidic media. This property proposes the use of (PAM-co-NaAlg) hydrogel as internal curing agent for concrete. The hydrogel is examined with cement weight ratios of (0.1-0.5) wt%. The study shows that cement with (PAM-co-NaAlg) hydrogel improves the compressive strength of cement at 0.1 and 0.2 wt%.