Investigation of the Spatial Variability and Correlation in Concrete in Structures Using the Rebound Method

The spatial variability and correlation of the physical and mechanical properties are important characteristics of concrete. This study systematically investigates the spatial variability and correlation of concrete in an actual engineering structure by the intensive rebound hammer tests. The test results show that there are significant differences in the probability distributions of rebound numbers among different components, as well as among different blocks. The rebound numbers in the structure exhibit multilevel variability: the hierarchical coefficients of variation of the rebound numbers within components, among different components and among different blocks is 0.054, 0.042, and 0.041, respectively. In addition, the rebound numbers within components also show significant spatial correlation, with a spatial variation ratio of 0.573 and a correlation length of 0.261 m. There is considerable variability in the correlation length among different blocks. To enhance the representativeness of the samples, a spatial sampling scheme for structures and a rebound scheme for concrete components were proposed based on the experimental results. The proposed spatial sampling scheme results in evenly distributed sampled components within the structure. The rebound scheme achieves accuracy exceeding that of the standard method while using only 30% of the sample points. These findings indicate that the proposed sampling and rebound schemes have high practical value in engineering applications, significantly improving the representativeness and accuracy of the rebound method.