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Non-destructive testing (NDT) techniques are crucial in making informed decisions about reconstructing or repairing building structures. The SonReb method, a combination of the rebound hammer (RH) and the ultrasonic pulse velocity (UPV) tests, is widely used for this purpose. To evaluate the compressive strength, C S , of the concrete under investigation, the ultrasonic pulse velocity V p and the rebound index R must be mapped to the compressive strength C S using a suitable conversion model, the identification of which requires supplementing the NDT measurements with destructive-type measurements (DT) on a relatively large number of concrete cores. An approach notably indicated in all cases where the minimization of the number of cores is essential is to employ a pre-existing conversion model, i.e., a model derived from previous studies conducted in the literature, which must be appropriately calibrated. In this paper, we investigate the performance of Gaussian process regression (GPR) in calibrating the pre-existing SonReb conversion models, exploiting their ability to handle nonlinearity and uncertainties. The numerical results obtained using experimental data collected from the literature show that GPR calibration is very effective, outperforming, in most cases, the standard multiplicative and additive techniques used to calibrate the SonReb models. [ABSTRACT FROM AUTHOR]

Abstract The evaluation of compressive strength in existing concrete buildings poses an engineering challenge, stemming from the development of structural sizing techniques. In this context, the evolution of non-destructive testing equipment and methodologies has allowed for a deeper analysis of the properties of the concrete under study and a reduction in the number of core extraction tests, which are more invasive techniques. Among the various approaches to strength estimation, the emergence of combined methods like SONREB (ultrasonic pulse velocity and rebound number) has stood out due to the comprehensive nature of the properties considered. However, the scarcity of real-world case study data and the challenges of in-situ evaluation hinder the consolidation and subsequent dissemination of this method, especially in Brazil. Thus, the present case study in a 95-year-old building allows the assessment of the effectiveness of different methods in estimating the compressive strength of the tested elements and the overall structure. The obtained results highlight the importance of calibrating the models to the reality of the analyzed structure and considering the effects of carbonation. Furthermore, the analysis of these results reveals the need to evolve the method in order to universalize it, given the low performance of the tested models. Despite this, it is noteworthy that the estimated overall average strength of the building is very close to the actual value, with an absolute error of approximately 2 MPa and a relative error of 8.5%.

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]

El estudio realizado tuvo como objetivo evaluar diferentes modelos SonReb para estimar la resistencia a compresión en elementos de hormigón armado fabricados con cemento y áridos cubanos. Se realizaron mediciones de índice esclerométrico y velocidad del pulso ultrasónico en 9 columnas diseñadas con mezcla de cemento Portland ordinario P-35. Se compararon 8 modelos, de los cuales los propuestos por RILEM y Tanigawa et al. mostraron un error inferior al 4% con respecto al valor de referencia, determinado mediante rotura de probeta. Los resultados obtenidos demuestran la factibilidad de uso de los modelos para la estimación de resistencia a compresión del hormigón, empleando materiales nacionales.

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.

To make the examination of the strength of existing building structures easier, can be done by using the NDT methods. It is therefore a study related to the combination of NDT and DT methods to obtain better accuracy of the results. The research uses PUNDIT PL-200, Silver Schmidt Hammer, Compression Testing Machine with 3 concrete quality types of 12,5 MPa, 18,75 MPa, and 25 MPa. Overall results, UPV and the actual compressive strength have a close and mutually affecting relationship between the variables evidenced by the R2 value of 0,7458. In addition, with the presence of combinations of several variables testing methods of DT and NDT, it can produce a level of accuracy from a compressive strength estimate value.

Ultra-High Performance Fibre Reinforced Concrete is a material which is becoming increasingly popular in structural applications, mainly due to its superior mechanical characteristics. The mechanical properties of this material are of high importance and the development of non-destructive techniques is vital for the evaluation of the mechanical characteristics of existing structures. In the current study, Ultra-High Performance Fibre Reinforced Concrete with different amounts of steel fibres has been examined. Compressive and tensile tests have been conducted alongside with Ultrasonic Pulse Velocity and Rebound Hammer measurements and the development of appropriate empirical non-destructive models has been examined. [ABSTRACT FROM AUTHOR]

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]