A Novel Method for Studying the Re-Swelling Capacity of Superabsorbent Polymers in An Artificial Crack

Re-swelling capacity is a key factor influencing the self-sealing efficiency of superabsorbent polymers (SAPs) in concrete. In this paper, a new parameter (re-swelling ratio, η), the volume ratio of the crack which was filled with the expansive SAPs and the dry SAPs, was given to quantify the re-swelling capacity of a single SAPs particle. An innovative immersion test was used to study the η value of SAPs in the hardened cement paste with an artificial crack. Moreover, the influence of the crack width and particle size on the sealing efficiency of SAPs in the cracked paste was investigated by a water permeability test. The results showed that the mass ratios of the expansive SAPs in an artificial crack were less than those in a free state. The η value of SAPs in the hardened paste with an artificial crack increased with the increase of the crack width due to the restricting effects of the crack. The expansive SAPs in the cracked paste could totally seal or partly seal the crack within the original void. Moreover, the sealing efficiency of SAPs slightly increased with the rise of the crack width (0.25 to 0.5 mm) and the reduction of the particle size. This research demonstrates that the crack width in concrete and the particle size of SAPs are the key factors influencing the re-swelling behavior of SAPs which should be taken into consideration when designing the self-sealing concrete containing SAPs.