Effect of type and particle size of superabsorbent polymers on the hydration mechanism of pavement concrete

Superabsorbent polymer (SAP) has been accepted as a novel internal curing component in pavement concrete because of its superior water absorption and retention capabilities. The effect of the characteristics of SAP on the hydration of pavement concrete and the understanding of the internal curing mechanism are crucial. In this paper, modified cement-based materials were prepared by incorporating non-ionic and ionic SAPs (SAP-AM and SAP-SA) with different size distributions. The influences of SAP type and particle size on the hydration kinetics, strength and internal relative humidity of pavement concrete were investigated. The results show that SAP-AM and SAP-SA improved the mechanical strength of specimens at 28 d by about 9.7% and 0.3%, respectively. SAP-AM lengthened the acceleration duration, and the delay effect of SAP-AM with the particle size of 80-100 mesh was greater. SAP-AM(200) decreased the conversion rate of capillary water to chemical bonding water, thereby reducing the hydration reaction at 1 d. Non-ionic SAP with a smaller particle size is an ideal internal agent for the effective curing of pavement concrete. These new findings may help to understand the hydration mechanism and provide suggestions for the selection of SAP type and particle size in internally cured concrete.