Enhancing concrete durability in chloride-rich environments through manual application of healing agents

Abstract

Concrete structures in chloride-rich environments are prone to deterioration, especially when ions can intrude via cracks towards the steel reinforcement. Self-healing concrete could significantly extend the service life of reinforced concrete. Hence, selecting appropriate healing agents to improve the durability is a critical challenge for the construction industry. This study investigates the use of three potential healing agents: water-repellent agent (WRA), sodium silicate (SS), and polyurethane (PU). The agents are tested separately under two conditions: exposure to a 3.3 % NaCl concentration at 20 °C and exposure to cyclic freeze-thaw conditions. The agents are manually injected into the cracks and evaluated for their healing efficiency using the capillary absorption test and microscopy analysis. Additionally, their resistance to freeze-thaw cycles by monitoring mass loss and chloride bulk diffusion is measured using sprayed silver nitrate, titration, and EDX mapping. The results demonstrate the effectiveness of PU in completely preventing chloride ingress and withstanding the freeze-thaw cycles. On the other hand, WRA showed a significant reduction in scaling, being the only healing agent to keep scaling below the appropriate scaling level of 1 kg/m2. Although WRA had the best performance in the scaling test and prevented chloride ingress, some influence was observed from the freeze-thaw cycles with regard to chloride ingress. Samples treated with SS performed better than the reference samples but did not show the same effectiveness as samples treated with PU or WRA in preventing chloride ingress. Overall, the study highlights the potential of healing agents in improving the durability of concrete structures in chloride-rich environments, with PU and WRA being the most promising for further development and optimization.