Exogenous healing in concrete with pH-sustained internal carbonation

Abstract

In this study, experimental investigations were conducted on enhancing the crack-healing potential of concrete using the internal carbonation process. The objective is to overcome one major limitation of autogenous healing (limited carbonation) by using Sodium Carbonate (Na2CO3) solution as a healing agent. To replicate the different types of damages and internal cracking that could arise during the service life of concrete structures, the effects of drying shrinkage and mechanical stresses on the crack-healing proclivity of cement-based materials were explored. A novel technique to measure crack-healing under constantly applied stress is also introduced for better assessment of healing in real-world situations. Results show a significant improvement in healing by using 0.95 M Na2CO3 solution over plain water. Moreover, permeability observations under stress revealed that the potential for healing by the proposed mechanism is strongly dependant on the stress level in samples. In the later part of the paper, Service Life Predictions were also undertaken by utilizing chloride ion diffusion coefficients extracted from the measured permeability coefficients and service life models available in the literature. Results from comparison of predicted service life indicate that at least in qualitative terms, healing with internal carbonation using the Na2CO3 solution led to an increase in the service life of concrete composites.