Carbonation Depth Test
Carbonation of concrete is a process by which carbon di oxide from the air penetrates into the concrete and reacts with calcium hydro-oxide to form calcium carbonates. In the presence of moisture co2 changes into dilute carbonic acid which attacks the reinforcement and also reduces alkanity of concrete.
This test is done or carried out by spraying an indicator on freshly exposed surfaces of concrete broken from the structure. Then carbonation depth is accessed by using a solution of phenolphthalein indicator that appears pink in contact with alkaline concrete with ph value in excess of 9 when the concrete is not carbonized. Colourless at lower levels of pH value when concrete is carbonated and the protective layer gets destroyed and the steel is exposed to corrosion.