Influence of water content investigation on GPR wave attenuation for early age concrete in natural air-drying condition

•The relationship between volumetric water content and EM wave attenuation.•Variation of amplitude ratio due to decrease of water content in concrete sample.•Direct and reflected wave ratio provides quantitative info to interpret GPR data.•The method can be applied to aid concrete quality and to control water content. In this study, an efficient application to evaluate water content of concrete in a non-destructive way in natural air-drying conditions by time-lapse Ground-penetrating radar (GPR) measurements is described. This was achieved by carrying out time-lapse GPR measurements on a concrete block with 2 GHz shielded antenna in 24 measurement days between day three and the 150th day of concrete casting. The characteristics of the electromagnetic (EM) wave are directly influenced by the presence of water content in a material. Change in water content results in variations in dielectric properties, including dielectric permittivity and conductivity. The study focused on variation of EM wave attenuation, which is related to direct and reflected wave amplitudes due to decrease of water content in the sample. In order to obtain a reflected wave a reinforced bar was embedded at 10 cm depth. The ratio of the direct wave and reflected wave on each measurement day decreased with respect to the reflection amplitude, due to concrete desiccation. These results are a guide to determining the relationship between volumetric water content (VWC) and EM wave attenuation. The method has significant potential on freshly produced young concrete samples to monitor their quality. The suggested method may also have potential for practical on-site studies to determine possible corrosion risk due to water intrusion.