INFLUENCE OF VOID’S SIZES AND LOCATIONS ON THE CONCRETE COMPRESSIVE STRENGTH

This paper evaluates the reduction in concrete strength due to the presence of voids. Twenty-one (6*12 inches) concrete cylinders are made with various void sizes and locations. The cylinders are divided into seven groups (three specimens each). A first group is a control group while the other six groups have internal voids. The voids are made by cubical foam with 3 different sizes, 1, 2 and 3-inch cubes. The cubes are placed at two different depth locations from the top, 3 and 6 inches respectively. A 3D- Ein-Scan-Pro Camera is used to map the surface conditions of each cube before testing. The images produced by the scan is used to identify the correlation between the failure loads and the surface conditions. Furthermore, the Impact Echo (IE) nondestructive test devise is used on the top of the cylinder. The NDT results are used for comparison between the destructive and nondestructive evaluation. Cylinders are tested under compressive pressure until failure. As anticipated, the testing results indicate that the larger void size reduces the compressive strength more than the smaller voids. In addition, when the void is located closer to the testing surface (top), the reduction in the strength is more than those located far from the tested surface. At the conclusion of this study, a strength reduction factor can be proposed for given void sizes and/or locations.