Polyacrylamide Hydrogel Containing Starch and Sugarcane Bagasse Ash: Synthesis, Characterisation, and Application in Cement Pastes and Mortars.

Internal curing is a process based on the addition of materials that function as water reservoirs in cementitious media. Superabsorbent hydrogels are an alternative that can be used as an internal curing agent, as they have the ability to absorb and release water in a controlled manner. In the present work, superabsorbent hydrogels based on crosslinked polyacrylamide in the presence of starch and sugarcane bagasse ash (SCBA) were developed and applied to mortars as an internal curing agent. The synthesized hydrogels were evaluated by SEM, FTIR, and swelling analysis. Cement pastes and mortars were produced using different amounts of hydrogel (0.03%, 0.06%, and 0.1% by weight). An analysis of the cement pastes and mortars revealed that hydrogel contributes to hydration, thus improving the quality of the product. Furthermore, the addition of 0.03% hydrogel by weight increased the mechanical resistance of the mortars in up to 26.8% at 28 days of curing as compared with reference (without hydrogel). To the best of our knowledge, this is the first study to use a hydrogel based on polyacrylamide crosslinked with starch and SCBA as a curing agent for mortars and cement pastes. This approach is environmentally friendly, because it uses a natural product (starch) and a byproduct from the sugarcane industry (SCBA).