Performance Evaluation of Interface of Reinforced Concrete and Repair Mortars by Microscopy

Concrete structures submitted to the action of the environmental hazards can produce deterioration, mainly the corrosion of reinforcing steel. The structural repair can be an efficient solution for this problem. Then, the technological know-how of the materials and repair techniques used are very important. The adherence of the repair mortars on the old concrete is a decisive requirement of performance and durability of any repair. On the other hand, methods of analysis of images are being used more and more to evaluate and to understand, in a more precise way, the behavior of the materials. The objective of this work is the evaluation of commercial mortars of repairs by microscopy. In this study, four types of mortar were utilized: 1) high-resistance shrinkage-compensating mortar, 2) polymer-modified mortar, 3) high-resistance shrinkage-compensating with fiber- and polymer-modified mortar, and 4) epoxy coating with a similar mortar to the substratum concrete. The experiment was made in two concrete blocks of each type of material repair. In this research, 247 micrographs were analyzed from 24 samples. The typical morphologic characteristics of those materials were studied by optic microscope (OM), by dark field technique, with magnifying lenses of 50, 100, 200, and 400 times, and the scanning electron microscope (SEM) by secondary electron. The main result was to characterize the linking form and extension of the adherence among the repair materials mentioned and the concrete evaluated by comparison of images.