Test and evaluation method of compressive strength of existing concrete structures

The compressive strength of concrete is a critical parameter that affects the design and evaluation of existing concrete structures. Variations in international testing standards significantly affect the quality-assessment outcomes of similar projects. This study systematically compares the concrete strength testing systems of China and Europe, focusing on two primary approaches: destructive testing (DT) such as core drilling and nondestructive testing by calibration (NDTBC). Using 360 components rebound and 240 core specimens, with concrete strength grades ranging from C30 to C70, from eight large datasets (24 small datasets) of four Chinese typical projects, a comparable database is established through standardized processing. The database includes unified sample quantities, core counts, height-to-diameter ratios, control of statistical dispersion, and statistical analyses. Key findings indicate that both the DT and NDTBC methods generally yield higher estimated strength values under Chinese standards than under European standards. In this study, the mean difference for the eight datasets using the DT method is 2.3 MPa, which represents 4.7% of the actual compressive strength. For the 24 datasets analyzed using the NDTBC method, the average difference is 4.7 MPa, 9.4% of the actual compressive strength. The discrepancy between Chinese and European standards is more pronounced in the NDTBC results than in the DT results. Overall, the Chinese standards show a strong economic orientation, while the European standards show a more stringent risk-aversion orientation.