Estimating in situ concrete strength combining direct and indirect measures via cross validation procedure

This paper proposes a new approach, based on the cross validation analysis of data, to establish reliable models for estimating the in situ compressive strength of concrete from the results of indirect tests, including Ultrasonic Pulse Velocity test and compressive test on microcores. The method was validated on a database obtained from an extensive diagnostic campaign performed on an existing building. The reliability of the proposed method was evaluated along with the results obtained by means of the Alternative 1 approach of EN 13791 standard by comparing the mean and the characteristic values of the estimated uniaxial compressive strengths issued from the two methods with the real ones obtained directly from the cores. Compared to the standard approach, the proposed method resulted in a better reliability in estimating the in situ compressive strength, even with a lower number of cores used to obtain the relationships.