Processing of electron microprobe data from the analysis of altered cementitious materials

The purpose of this paper is to present a method for processing electron microprobe data coming from the analysis of degraded cementitious materials. The application domain is that of cement matrices exposed to attack by aggressive media inducing the leaching of one or more chemical elements from the cement paste — typically attacked by neutral or acid aqueous environments. As raw data obtained from electron probe microanalysis (EPMA) come in the form of relative quantities of elements, the aim of the processing is to obtain the absolute variation of the specimen's chemical composition in the degraded zone and consequently to allow a better understanding of the degradation mechanisms by the aggressive environment under consideration. This method was designed for degraded specimens in which the porosity was not filled with resin before the EPMA. The method uses the titanium content of the cement matrix as a control, this element being stable during attack by neutral or acidic media. The method is described in detail using the example of the attack of cement pastes by a mix of several organic acids (notably acetic acid) at pH 4. The use of EPMA for sound and altered cement pastes is also validated. The application domain of the correction method is discussed.