How Investigators Can Assess Concrete Strength with On-site Non-destructive Tests and Lessons to Draw from a Benchmark

A benchmark is carried out in order to compare how 13 experts define and can carry out an NDT investigation program and derive strength values from NDT measurements. The benchmark is based on simulations, which reproduces a synthetic data set corresponding to a grid of twenty 3m-high columns defining the structure of a building made up of beams and columns. The experts must assess the mean and the standard deviation of compressive strength. Three levels of assessment are considered corresponding to different quantities of test results (destructive or non destructive) available for the experts. The comparison of the various strategies used by the experts and the analysis of results enables the identification of the most influential parameters that define an investigation approach and influence its efficiency and accuracy. A special emphasis is placed on the magnitude of the measurement error. A model of the investigation strategy is also proposed.