Alginate biopolymers: Counteracting the impact of superabsorbent polymers on mortar strength

•CaAlg exhibits a strong moisture uptake capacity especially at air RH.•NaAlg becomes insoluble in mortar due to the divalent cations present in CF.•CaAlg leads to only a small compression strength reduction <15% upon 1 m% addition.•All alginates except NaAlg 1 m% meet the strength demand of 52.5 MPa at 28 days.•Alginate can be considered a very promising material in concrete applications.

Synthetic superabsorbent polymers (SAPs) are used in concrete for various applications. However, the addition of SAPs may lead to a significant decrease in mortar strength. In order to overcome this bottleneck, the present work focuses on the application of biopolymers as SAPs, more specifically polysaccharides including both uncross-linked sodium alginate as well as physically cross-linked calcium alginate. Interestingly, results indicate no or a limited (i.e. < 15%) reduction in strength upon introducing 1% relative to cement mass. Alginate can therefore be considered a promising material, not only for internal curing but even when high SAP amounts are required.