Hydrogels Based on Polyacrylamide and Pectin Containing Rice Husk Ash: Preparation, Characterization and Application in Formulation of Cementitious Materials

Superabsorbent polymers (PSAs) have been extensively studied to act as internal curing agents in cementitious materials, as they have the characteristic of absorbing and releasing water in a controlled manner, which can contribute to the hydration process of a cementitious medium during its consolidation. Thus, hydrogels consisting of polyacrylamide (PAAm), pectin (Pec) and rice husk ash (RHA) were synthesized to be applied in cementitious matrices. In addition, the PSAs were characterized by FTIR, SEM, and XRD. For evaluating the usage of hydrogels as internal curing agents, different hydrogel contents-0.03, 0.06, and 0.1 (wt-%, relative to cementitious components)-were used for mortar preparation. The mechanical strengths of the cementitious materials were evaluated at day 7 and day 28 during the curing process. The addition of PSAs to the mortars caused an increase in mechanical resistance such that the 0.06% content presented better performance at day 7 of curing (4.07% higher) and at day 28 of curing (8.06% higher) when compared with the reference mortar (without the addition of PSAs) in the same curing periods. This work demonstrates that the addition of PSAs contributes to the hydration of a cementitious material, improving the mechanical resistance of the studied mortars.