Application of cross-linked poly(acrylic acid)-poly(styrene-alt-maleic anhydride) core-shell microcapsule absorbents in cement mortars

We synthesized core-shell microcapsule absorbents with crosslinked poly(acrylic acid) (PAA) as the core and poly(styrene- alt -maleic anhydride) (cPAA-PSMA) as the shell by the precipitation polymerization method for delayed absorption of excess water in cement mortar. To control the shell thickness, cPAA-PSMA capsules were synthesized with the core-to-shell monomer mass ratios of 1: 0 (cPAA #1), 1: 0.5 (cPAA-PSMA #2), 1: 1 (cPAA-PSMA #3), and 1: 1.5 (cPAA-PSMA #4). The viscosity of the cement paste with cPAA-PSMA #4 absorbent increased slowly until 90minutes after absorbent addition, beyond which it increased rapidly. This suggests that mortars with cPAA-PSMA #4 absorbents can secure up to 90 minutes of working time. Incorporation of 1.0 wt% cPAA-PSMA #4 into cement mortar increased the compressive and flexural strengths by approximately 35% and 22%, respectively, compared to those of cement mortars without absorbents.