Carrageenan-based superabsorbent biopolymers mitigate autogenous shrinkage in ordinary portland cement

We report the synthesis and characterization of biobased superabsorbent copolymers from κ-carrageenan and poly(acrylic acid) that mitigate autogenous shrinkage in ordinary portland cement paste. Synthesized via free radical graft polymerization, the biobased superabsorbent polymers (SAPs) were characterized with regard to their thermochemical properties and swelling behavior in both aqueous and ionic solutions. The biobased SAPs were incorporated into cement paste to investigate their ability to mitigate autogenous shrinkage cracking in high-performance concrete. Results demonstrate that the biobased SAPs absorb up to 438 and 94 [g/g] (by mass) in aqueous and ionic solutions, respectively, after 24 h. Furthermore, the biobased SAPs were successful in mitigating shrinkage in low water-to-cement ratio pastes. While the control paste exhibited negative strain and ultimate shrinkage cracking, the samples containing biobased SAP experienced net-positive expansion during cement hydration.