A state-of-the-art review on the carbonation process in cementitious materials: Fundamentals and characterization techniques

Diagnostics of Concrete and Steel in Elements of an Historic Reinforced Concrete Structure

“…Each of them has its own advantages and disadvantages. The advantages and limitations of many methods have been discussed by Qiu [ 22 ].…”

“…The limitations of this method also result from the phenolphthalein specificity, which can evaporate from the concrete surface in the period between the application and the measurement. As a result, the phenolphthalein concentration can change, which may affect the concrete colouration [ 22 ]. Time plays an important role in this type of test because of the individual phases of the cement matrix of concrete colour at different rates [ 66 ].…”

“…Meanwhile, depassivation of steel occurs when the pH drops to 11.5–11.8 [ 10 , 21 ]. For this reason, in colourimetric tests other indicators are also used, e.g., timoloftaleine, alizarin yellow R, alizarin yellow GG, or T F PLPt [ 22 , 67 ]. Thymolphthalein changes colour at a pH of 9.3–10.5, while T F PLPt can be used for pH tests in the range 11.0–13.5.…”

“…In reinforced concrete structures, concrete (if it is tight enough, was made according to the appropriate recipe and has the right thickness) is the basic and best protection for the reinforcement [ 10 , 11 , 13 , 21 , 22 ]. The protective role of concrete is related to its alkaline reaction (pH ≈ 12.5–13.5), giving the effect of passivation at the interface between concrete and steel (formation of a micro-layer with very low ionic conductivity), which for all practical purposes prevents corrosion of the bars.…”

“…Most often the deterioration is the effect of carbon dioxide in the air and changes in temperature and humidity of the environment, which leads to gradual carbonation of concrete and directly affects the loss of the protective properties of the cover in relation to the reinforcement [ 10 , 11 , 21 , 22 , 23 , 24 ].…”