Mitigating Autogenous Shrinkage by Using Recycled Superabsorbent Polymers

Cracks may appear in cementitious materials with a low water-to-binder ratio. These early age cracks during the autogenous deformation have an impact on the durability of structures. Superabsorbent polymers used as internal curing materials may mitigate autogenous shrinkage, and thus may improve durability. In the interests of the circular economy, recycled superabsorbent polymers can be added to building materials, instead of commercially available superabsorbent polymers. In this paper, the influence of the addition of recycled SAPs from the diaper industry on autogenous shrinkage as well as on compressive and flexural strength, and free shrinkage was evaluated. The aim is to verify whether the improvement of the autogenous deformation is not at the expense of the mechanical properties of the cementitious material. Various tests were performed to assess the mechanical properties and shrinkage behaviour of specimens containing recycled superabsorbent polymers compared to reference preparations and specimens with commercially available superabsorbent polymers. The addition of recycled SAPs has a limited influence on the material’s properties compared to the addition of commercial SAPs. By partly mitigating autogenous shrinkage, recycled admixtures postpone the early-age cracking and seem to be a solution to improve cementitious materials durability and sustainability. The same behaviour was observed with regard to the free shrinkage tests.