Thymolphthalein as alternative to phenolphthaleine in concrete carbonation testing
Phenolphthalein is used in carbonation test of concrete. It is however a recognized carcinogen. Thymolphthalein has been used as an alternative with good results.
Thymolphthalein is not included in the harmonized EU classification and is not on the lists with substances currently known to fulfill SUBSPORT screening criteria for hazards of high concern.
See also Further reading.
Carbonation process causes the pH of concrete to drop and affects the passivity of the reinforcing steel, posing a threat to constructions, especially those exposed to environment.
The carbonation is generally tested with phenolphtaleine which gives a colour change indication.
The study consider that phenolphthalein has a reliability problem regarding test results. It is also a carcinogen chemical.
It was find that thymolphthalein was the best substitute for phenolphthalein.
The substitution of phenolphthalein for concrete carbonation determination is easy to implement. Costs of alternative reagent are a bit higher, yet comparable.
For determining the very early carbonation of concrete (before concterte setting), a mixture that still contains phenolphtalein is needed.
MSDS Thymolphtaleine from Sigma Aldich is here
ECHA C&L inventory ( retrieved on 25 February 2012)Further languages available
Type of information supplier
Yu, Myoung-Youl Yu, Lee, Jae-Yong ,Chung, Chul-Woo ,The Application of Various Indicators for the Estimation of Carbonation and pH of Cement Based Materials, SEDL / Journals / Journal of Testing and Evaluation (JTE) ,Volume 38, Issue 5 (September 2010)Type of publication and availability
Publication or last update: 27.02.2012