Evaluation of the effectiveness of the use of indicator methods in determining the carbonization of concrete

Abstract

Currently, one of the most important problems is the impact of aggressive environments on reinforced concrete structures, as a result of which the process of their destruction is triggered. One of the reasons for the failure of reinforced concrete structures is the process of carbonization of concrete. In practice, in order to timely eliminate and prevent the problem of carbonization of concrete, an indicator method for determining damaged zones is used. However, the traditional phenolphthalein test method does not allow to determine with high accuracy the boundary zones of concrete that are most vulnerable to carbonization. The article discusses the possibility of improving the phenolphthalein test method by using additional solutions of acid-base indicators alizarin and neutral red. The results of experiments on measuring the surface neutralized layer of concrete with alcohol solutions of acid-base indicators alizarin and neutral red on concrete samples of various ages and sizes are presented. The results of a comparative analysis of the traditional and improved methods for determining the carbonization of concrete are presented. The method proposed by the authors is distinguished by greater accuracy of the results obtained. The solution of neutral red expands the boundaries of the application of the phenolphthalein test method for determining the carbonization zones of concrete at 6 < pH < 10.5. The use of alizarin in addition to the phenolphthalein solution is difficult because the indicator solution is too dull in color, resulting in the definition of zones of highly alkaline concrete not being accurate enough. Due to the fact that the phenolphthalein test method has limitations in its use by examiners at the field stage, it is advisable to continue the search for indicators that can supplement or fully replace phenolphthalein for these purposes.