The application of synthetic aperture radar imaging technique to measure moisture content of concrete structures

The presence of free moisture inside concrete is a significant cause of deterioration (e.g. alkali-silica-reaction-ASR, steel rebar corrosion, freeze-thaw) in reinforced concrete structures. A 10 GHz synthetic aperture radar system was used to scan five concrete specimens with water-to-cement (w/c) ratios ranging from 0.35 to 0.55 and at moisture contents varying from dry (0.25%) to saturated (4.8%). The experimental data were used to develop a regression model, which illustrates an important relationship between the SAR image and moisture content at a specified w/c ratio. The model indicated that integrated SAR amplitude increases non-linearly with the moisture content of concrete at a given w/c ratio. The study concludes that the inverse of the developed model is adequate for estimating in-place moisture content of concrete using SAR imaging techniques and that the w/c ratio has a significant effect on the developed relationship. (C) 2019 Elsevier Ltd. All rights reserved.