Early Detection of Honeycombs in Concrete Pavement Using GPR

The goal of this research is to evaluate whether it is possible and effective to detect honeycombing of concrete pavement using a ground-penetrating radar (GPR) during construction. The motivation is that identifying honeycombing of concrete during construction would help avoid the spread of consolidation problems in large pavement sections, which are costly and time consuming to repair. GPR has been used as a tool for concrete quality control and detection of delamination in reinforced concrete elements since the 1980s, but it has not been used for the early detection of relatively small air voids. In this project, first, preliminary field testing was conducted to determine the possibility of detecting honeycombs in existing concrete pavement. Then, air voids of different sizes, shapes, and depths were artificially created using spray-foam in several laboratory specimens and detected using a high-frequency GPR antenna at different times after concrete placement. Cores were extracted to validate GPR readings and determine the capability of this technique. Another field testing was conducted to evaluate the efficiency and economy of using GPR as a nondestructive quality control tool. Field and lab test results indicated that GPR could be efficiently used to detect air voids as small as 32 mm (1.25 in.) and as deep as 102 mm (4 in.) from the surface of the concrete pavement as early as the initial set of concrete. These findings suggest that GPR is an effective, efficient, and economic quality control tool for this application.