Synthesis and Characterization of Superabsorbent Polymer Hydrogels Used as Internal Curing Agents: Impact of Particle Shape on Mortar Compressive Strength

Abstract

Superabsorbent polymer hydrogels have proven to be effective internal curing agents for high-performance concrete because of their ability to absorb and release large amounts of water during hydration and thus mitigate autogenous shrinkage. In this study, the impact of hydrogel particle shape on the microstructure and compressive strength of internally cured mortar was experimentally determined. Inverse suspension polymerization was used to synthesize spherical poly(sodium-acrylate acrylamide) hydrogel particles, while solution polymerization was used to create similarly sized angular particles with identical chemical composition. The hydrogels were characterized with swelling tests in water and cement pore solution. Particle shape did not impact the swelling behavior, and micrographs confirmed that the particles maintained their shape during mixing and placement. Despite the introduction of spherical- and angular-shaped voids from the swollen hydrogel particles, there were no significant differences observed between the compressive strengths of the control mortar and the mortars containing either the spherical or angular hydrogel particles.