ON THE DETERMINATION OF CARBONATION IN CEMENTITIOUS MATERIALS

For material testing, qualification and subsequent assessment fast, simple, reliable and economic methods are needed. This paper provides an overview ofdifferent techniques to determine the depth of carbonation in cementitious materials. The easiest and cheapest way is to remove a core or a fragment of concrete cove rand spray a colour indicator on the fresh fractured surface (by splitting). Here, 1% phenolphthalein in 70% ethanol is most widely used. However, this only indicates in which area the concrete has a pH value below 8.2-10, but not the actual carbonation front which is on average about 20% higher. Since phenolphthalein is carcinogenic, alternative colour indicators were investigated in the laboratory. 0.5% Curcumin showed similar colour change to phenolphthalein. In addition, 0.1% thymolphthalein proved to be an alternative. Scattering within one measurement was lower than for phenolphthalein and the results were closer to the carbonation depths determined by different analytical methods (TGA and LA-ICP-MS). Furthermore, the transition pH-value of thymolphthalein is in the area of 9.3-10.5which is closer to the actual carbonation front, allowing a more accurate assessment of the risk of reinforcement corrosion.     «

For material testing, qualification and subsequent assessment fast, simple, reliable and economic methods are needed. This paper provides an overview ofdifferent techniques to determine the depth of carbonation in cementitious materials. The easiest and cheapest way is to remove a core or a fragment of concrete cove rand spray a colour indicator on the fresh fractured surface (by splitting). Here, 1% phenolphthalein in 70% ethanol is most widely used. However, this only indicates in which area t...     »