Volume 38, Issue 5 (September 2010)
The Application of Various Indicators for the Estimation of Carbonation and pH of Cement Based Materials
Carbonation decreases the pH of the concrete and breaks the passivity of reinforcing steel. Therefore, carbonation is related to potential rebar corrosion even though carbonation itself does not directly damage the integrity of the concrete. The phenolphthalein method, which is the most often used method of determining carbonation, however, has a reliability problem. Therefore, this research mainly focuses on the use of various indicators to find the possible substitutes for phenolphthalein. The early carbonation and pH of the carbonated specimen was also investigated using various indicators. It was found from the results that thymolphthalein was the best substitute for phenolphthalein, and a combination of phenolphthalein and thymolphthalein, tropaeolin O, and indigo carmine enabled us to estimate the early carbonation. This research also reported the successful application of various indicators which can be extended for the pH estimation of solid mortar specimen.