Characterisation of the variations of tint and the adhesion of pigments onto the surface of mortar

A method, coupling Particle-Induced X-ray Emission (PIXE) and colorimetry, is proposed to determine the amount of pigments transferred from the casting mould and to quantify their adhesion onto the surface of coloured mortar about 4 weeks after demoulding. PIXE analyses allow the quantification of the amount of pigments anchored onto the hardened mortars, even if the observations by Scanning Electron Microscopy (SEM) remain necessary to study the near-surface microstructure, especially for the rough samples. The optical parameters deduced from the colorimetry measurements are more interesting to establish the homogeneity of the perceived tint. Indeed, a protocol is proposed to evaluate the adhesion of the pigments by relating the amount of pigments (detected by PIXE analyses) and the coordinates measured in the CIE (L∗, a∗, b∗) colour space, before and after a water washing test.