Sustainable Biobased Hydrogel as an Alternative Air-Entrainment Agent in Cement-Based Materials

This study synthesized a biobased hydrogel from local and renewable raw materials to improve the freeze–thaw resistance of hardened cementitious matrices. A biobased hydrogel was produced by thermal gelatinization process with different cornstarch contents ranging from 1% to 3% of mortar mixing water. The effectiveness of cornstarch hydrogel was gauged by comparing its void structure with those of two commercially available super absorbent polymers (used at 0.2% of cement weight) and an air-entraining agent (0.49% of total mortar weight). The resulting void structures were analyzed by evaluating porosity, void-size distribution, spacing factor, and shape of voids using microcomputed tomography scanning with a sensitivity of 10 μm. The 3% cornstarch hydrogel produced a robust void structure with high porosity and relatively large number of smaller voids. The high porosity was achieved without a significant reduction in compression strength. Furthermore, chemical analysis revealed that the 3% cornstarch hydrogel had a positive influence on the hydration of cement compared with the commercial air-entrainment agent. Overall, the 3% cornstarch hydrogel can be a sustainable biodegradable replacement for traditional and commercial surfactants for air entrainment, and has an additional internal curing advantage.