Effect of crack widths and water pressures on crack sealing behavior of cementitious materials incorporating spherical superabsorbent polymers

Although several studies have been conducted using bulk-polymerized superabsorbent polymers (SAPs) with irregular shapes in cementitious materials, studies on the use of spherical SAPs prepared via inverse suspension polymerization are relatively scant. In addition, in terms of crack sealing by SAPs, few studies have focused on the behavior of SAPs with varying hydraulic pressures and crack widths. In this study, we investigated the effect of crack widths and water pressures on the crack sealing behavior of spherical SAPs in cementitious materials. The flow rate through the crack increased as the water pressure increased, but the flow rate reduction (φ) due to rapid swelling of SAPs remained constant at pressure gradients ≤16.667 mm/mm. X-ray computed tomography (CT) measurements showed that almost all spherical SAPs were split by cracking, resulting in a reduced crack sealing efficiency at crack widths over 0.15 mm. However, below this width, the loss of sealing efficiency due to split SAPs was offset. In addition, based on the test data, the accuracy of the existing model for predicting φ was improved. The modified model may be limited to specific types of spherical SAPs, but it is expected to provide highly reliable predictions of φ.