Study on the Synergistic Effect of Superabsorbent Polymer and Crystalline Admixture on Self-Healing Performance of Mortar Based on Image Binarization Method

Abstract

Concrete self-healing technology is an effective method for autonomously repairing cracks, which can reduce the maintenance costs of concrete components and prolong their service life. This study investigates the mechanical properties and self-healing abilities of mortar with internally mixed superabsorbent polymers (SAPs) and crystalline admixtures (CAs). The compressive strength and recovery rate of the specimens were evaluated, and the self-healing performance of concrete specimens was assessed through water absorption tests and optical microscopy observation of healed cracks. Microscopic analysis of the crack fillings was conducted using SEM-EDS and XRD tests, revealing the mechanism of the synergistic effect of SAPs and CAs on self-healing. The results indicate that the physical filling effect of SAPs’ water absorption and expansion almost completes the healing action before the 7-day healing age, with a weakened healing ability after this age. The chemical action of CA activation continues to heal cracks up to the 90-day healing age. When SAPs and CAs are incorporated together into the concrete matrix, the mortar specimens exhibit the best healing ability before the 7-day healing age. As water is released from the SAPs, the ongoing activation reaction of CAs shows the most effective healing result at the 90-day age. SEM-EDS analysis confirmed that the addition of CAs increases the Ca/Si ratio of calcium silicate hydrated, transforming it from an amorphous cluster structure to a needle-like structure. Furthermore, the internal curing effect of SAPs promotes the activation reaction of CAs, resulting in a greater quantity of more densely structured calcium silicate hydrated.