This study proposes a method of estimating the distributions of voids and strength within concrete by contrast X-ray [1-3] using cores 100 mm in diameter drilled from actual concrete structures. Contrast X-ray is characterized by its capability to detect cracks…
This study proposes a method of estimating the distributions of voids and strength within concrete by contrast X-ray [1-3] using cores 100 mm in diameter drilled from actual concrete structures. Contrast X-ray is characterized by its capability to detect cracks and voids within concrete by radiographic imaging after impregnating specimens with a contrast medium. The detected values were then quantified and related to the strength. This technique was also applied to small diameter cores to examine if similar measurement is possible by slight destruction. Also, cores were drilled from concrete structures damaged by alkali-silica reaction (ASR). These were subjected to contrast X-rays to investigate the image characteristics of cracking, with which the feasibility of this method for judging ASR was confirmed. The test results demonstrated that the strength of concrete can be accurately estimated from specimens 10 mm in thickness. This method also enables to determine the strength distribution in drilled cores from the surface inward. In regard to tests on cores of different sizes, smaller cores led to greater scatters of void and strength distributions, but these scatters were found to be attributed to scatters of concrete as such. Measurement of void distribution in ASR-affected concrete revealed great changes in void properties when compared with sound concrete. Early ASR may therefore be evaluated by monitoring these void characteristics.