Study of interactions between sodium monofluorophosphate and hardened cement paste and their consequences on concrete transfer properties

Surface applied corrosion inhibitors are one of the methods used to protect embedded reinforcing bars from corrosion. This paper presents a study of interactions that can occur between sodium monofluorophosphate (MFP) and concrete during its transport from the applied surface to the steel. Interactions of MFP with portlandite have clearly been observed with X-ray diffraction diagrams. Tests with solutions have been realised, and show that an amorphous gel appears when MFP is in contact with a saturated calcium hydroxide solution. Percolation tests have highlighted the consequences of these reactions on concrete properties. In the last part of this study, quantitative chemical analysis of the percolate is presented: they show that when the concentration of the MFP solution increases, more MFP is found in the percolate even if a large part is kept in the concrete sample.