Evaluation and comparison of traditional methods and Electron Probe Micro Analysis (EPMA) to determine the chloride ingress perpendicular to cracks in self-healing concrete

Abstract

The appearance of cracks in reinforced concrete structures accelerates the penetration of aggressive substances such as chloride ions into the concrete matrix. This leads to durability problems due to the accelerated onset of chloride induced reinforcement corrosion. Chloride ions penetrate the concrete matrix along the crack tip and also along the crack walls in a direction perpendicular to the crack. This research focused on the application of autonomous crack healing by encapsulated polyurethane as a method to reduce (perpendicular-to-crack) chloride ingress. Three investigation methods were applied: profiling by grinding followed by potentiometric titration, visualization of the chloride penetration front using AgNO3 and Electron Probe Micro Analysis (EPMA). The proposed healing mechanism proved to be efficient to reduce the chloride concentrations in the direct vicinity of the crack and to cause a reduction of the perpendicular-to-crack chloride penetration. Furthermore, the results found by the different evaluation methods were comparable to each other. In this sense, the data obtained by EPMA contained most of the information that was obtained by the AgNO3 spray method and the chloride profiling together. This proves that EPMA is a powerful technique for analyzing the chloride penetration in concrete and a valuable tool to determine the crack healing efficiency of self-healing concrete.