The re-swelling behavior of superabsorbent polymers (SAPs) in hardened cement paste with an artificial crack

Re-swelling capacity is a key factor affecting the contribution of superabsorbent polymers (SAPs) to sealing cracks in concrete. In this paper, a new parameter (η), the ratio between the volume of the crack filled with the expansive SAPs and the volume of dry SAPs, is given to evaluate the re-swelling capacity of a single SAPs particle. Moreover, the influences of paste composition, solution properties, and crack width on the η value are studied by an innovative immersion test. The results show that the swollen volume ratio, the ratio of the swollen volume of SAPs during mixing to their dry volume, decreases with the reduction of the water-to-binder ratio and the addition of mineral admixtures. Furthermore, the swollen volume ratio, the solution properties, and the crack width have significant impacts on the η value. The η value rises with an increase in crack width (0.25–1 mm), revealing the restricting effects of cracks on the re-swelling capacity of SAPs. These results indicate that the paste composition, solution properties, and crack width should be considered when designing the self-sealing concrete containing SAPs.