Efficiency of the saturation of concrete with liquid under vacuum conditions

The saturation of concrete with liquid under vacuum conditions is commonly recognized as the most efficient saturation technique. Therefore, this technique is recommended to be performed in porosity measurements (to determine the water-accessible porosity) and in chloride diffusion/migration tests (to ensure that the diffusion/migration the only transport mechanism of chlorides during the test). The efficiency of vacuum saturation was analyzed in this study by saturating concrete samples with a chloride solution (chloride is used as a tracer). After performing the vacuum saturation, the chloride penetration depth in several split samples was detected using a colorimetric indicator for chlorides, while in other samples the chloride concentration was measured at different depths. The observed chloride penetration depths indicate that the external chloride solution could not access the entire volume of the saturated samples. The measured chloride concentration profiles show that the chloride concentration gradually decreases from its maximum at the surface to lower concentrations in the deeper layers of concrete. From the results presented in this study it may be concluded that the vacuum saturation does not ensure a complete liquid-saturation of concrete, regardless of the quality (permeability) of the latter or thickness of the sample in the investigated range (of 15 up to 50 mm).