Effect of superabsorbent polymers on mechanical strength and cracking of mortar and concrete with water to cement ratios of 0.4 and 0.5

Abstract

Most studies of adding superabsorbent polymers (SAP) into concrete focus on high-strength concrete, while this paper aims to understand the influence of SAP on "ordinary concrete" at a w/c ratio being 0.4 or 0.5. The proposed experiments include the effect of particle size, mixing methods, and dosages on the restrained shrinkage and mechanical properties of mortar and concrete. Mortar with varying dosages of SAP (0.1, 0.2, and 0.3 wt.%) and two types of SAP (type-a of 30-60 mesh and type-d of 300-400 mesh) was studied to evaluate the effect of SAP on mortar's cracking and strength. Two mixing processes of SAP (dry and pre-wetted) were used to examine the effect of SAP on the mortar's shrinkage and mechanical properties. Furthermore, concrete specimens with a w/c ratio of 0.5 were prepared to investigate the cracking performance of concrete using the restrained squared concentric ring test method, a new approach which can predict the cracks location and pattern to evaluate the restrained shrinkage of concrete. The result revealed that the addition of SAP in a prewetted state decreased the mechanical properties at early curing age. The addition of 0.3 wt.% SAP was found to have mitigated the restrained shrinkage while prolonging the time to cracking of cementitious composites. The major finding is that adding SAP to ordinary concrete reduces shrinkage and improves mechanical strength, which should be further looked into and explored in its application in engineering work.