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Determining the compressive strength of concrete is important in all phases of construction and in diagnosing the technical condition of existing reinforced concrete buildings and facilities during their service. In this article, the author presents the experimental results from research conducted over 6 years. The following non-destructive methods were used in the tests—elastic rebound, ultrasonic, SonReb and destructive methods, and the results of the latter were used as a reference. The tests were carried out on specimens prepared on the day of laying the concrete mix in the reinforced concrete beams or cores taken from the beams. The results of the determination of the probabilistic compressive strength using the different methods at concrete ages of 28, 244, 280, 293, 342, 1126 and 1926 days, are presented. The relative error, predicted strength and accuracy were determined and compared. Isocurves were drawn to determine the compressive strength for each point of a reinforced concrete structure based only on measurements obtained using non-destructive methods. The results obtained via SonReb and via the method assessing ultrasonic pulse velocity and its relationship to the dynamic and static modulus of elasticity were the closest to the reference compressive strength values. [ABSTRACT FROM AUTHOR]

This document discusses the results obtained in the estimation of compression strength through the readings of the rebound hammer and ultrasonic pulse velocity on 9 columns of reinforced concrete. The estimation was performed by applying different SonReb models. The objective of the study is to evaluate which of the applied models is more consistent with the compression resistance value of 27.0 MPa obtained by press-breaking assay, for concretes manufactured with Ordinary Portland Cements P-35 (Type I) of domestic production and aggregates from Cuban quarries. The results obtained showed that the models proposed by RILEM and Tanigawa et al. were closest to the reference value with percentage difference below 4%. This research will allow the performance of non-destructive tests with more accurate results, in the restoration processes of the Historic Center of Havana, Cuba. [ABSTRACT FROM AUTHOR]

Determining the compressive strength of concrete is important in all phases of construction and in diagnosing the technical condition of existing reinforced concrete buildings and facilities during their service. In this article, the author presents the experimental results from research conducted over 6 years. The following non-destructive methods were used in the tests—elastic rebound, ultrasonic, SonReb and destructive methods, and the results of the latter were used as a reference. The tests were carried out on specimens prepared on the day of laying the concrete mix in the reinforced concrete beams or cores taken from the beams. The results of the determination of the probabilistic compressive strength using the different methods at concrete ages of 28, 244, 280, 293, 342, 1126 and 1926 days, are presented. The relative error, predicted strength and accuracy were determined and compared. Isocurves were drawn to determine the compressive strength for each point of a reinforced concrete structure based only on measurements obtained using non-destructive methods. The results obtained via SonReb and via the method assessing ultrasonic pulse velocity and its relationship to the dynamic and static modulus of elasticity were the closest to the reference compressive strength values.

Abstract: This paper analyzes why and how nondestructive testing (NDT) measurements can be used in order to assess on site strength of concrete. It is based on (a) an in-depth critical review of existing models, (b) an analysis of experimental data gathered by many authors in laboratory studies as well as on site, (c) the development and analysis of synthetic simulations designed in order to reproduce the main patterns exhibited with real data while better controlling influencing parameters. The key factors influencing the quality of strength estimate are identified. Two NDT techniques (UPV and rebound) are prioritized and many empirical strength-NDT models are analyzed. It is shown that the measurement error has a much larger influence on the quality of estimate than the model error. The key issue of calibration is addressed and a proposal is made in the case of the SonReb combined approach. It is based on the use of a prior double power law model, with only one parameter to identify. The analysis of real datasets from laboratory studies and from real size buildings show that one can reach a root mean square error (RMSE) on strength of about 4MPa. Synthetic simulations are developed in order to better understand the role played by the strength range and the measurement error. They show that the number of calibration cores can be significantly reduced without deteriorating the quality of assessment. It is also shown that the optimal calibration approach depends on the number of cores. [Copyright &y& Elsevier]