More and more, one needs to prove that the materials do not alter the environment in which they are located. For example, it must be guaranteed that they release none or little substances (such as metals and organic molecules) when they are brought into contact with water. This phenomenon is commonly called « leaching ».
Already published results have established this evidence for the metallic trace-elements in the case of mortar and concrete in contact with potable water. The CRIC-OCCN has been a precursor in this domain and has shown that these traces are very small and in the order of ppb (µg/kg).
Considering organic molecules, studies remain rare. Indeed, existing one show that for usual quantities of admixtures, the leaching rate remains lower than the analytical limit of detection which is about 500 µg/l. However, it could be objected sometimes that a leaching rate smaller than 500 µg/l wouldn’t be a sufficient guarantee regarding the limits for other substances in the order of µg/l.
This PhD-study, initiated by ATILH has been performed at the University of Metz and at the CRIC-OCCN. It has allowed with help of very sophisticated analytical techniques (Time of flight Mass Spectrometer for example) to decrease the detection limits of three types of organic molecules in the leachant obtained by the accelerated leaching of pure pastes in contact with water (manufacturing help agent, TEA; Superplastifier, PCE and its polymerization residue). This study enabled to show that, even with an accelerated leaching process, the molecules traces found in the leachant are extremely small and at the level of the detection limits. This study will continue or by a new ph. D. thesis or by a European sponsored Research.
This study will be continued by a new Ph. D. thesis starting in 2012, that will study the trapping mechanisms of the organic molecules in the cement matrix. A feasibility study is actually performed.