Non destructive assessment of in situ concrete strength: comparison of approaches through an international benchmark

Breysse, Denys; Balayssac, Jean-Paul; Biondi, S; Borosnyói, Adorján; Candigliota, E; Chiauzzi, Leonardo; Garnier, Vincent; Grantham, Michael; Güneş, Oğuz; Luprano, V.A.M.; Masi, Angelo; Pfister, Valerio; Sbartaï, Zoubir Mehdi; Szilágyi, Katalin; Fontan, Maxime

doi:10.1617/s11527-017-1009-7

Cited by 34 publications

(17 citation statements)

References 10 publications

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“…The study examines the effects of internal stress on cubes and the shape of the impact area of a cylindrical test specimen on the measurement results using rebound hammers for HSC testing. [31]). Three cube test samples of concrete were used to determine the compressive strength of concrete for each given age and class of concrete.…”

Section: Test Specimen Shapementioning

confidence: 99%

Rebound Hammer Tests of High-Strength Concrete: Effects of Internal Stress and the Shape of the Impact Area of the Test Specimens on the Measurement Results

Bodnárová¹,

Brožovský²

2019

Period. Polytech. Civil Eng.

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This study examines the factors affecting the results of non-destructive testing of high-strength concrete performed on cubes and on cylinders and examines the processing of calibration relations. Tests were performed with both a type N and a type L Schmidt impact hammer (with a standard impact energy of 2.205 Nm and 0.735 Nm respectively). The assessed factors were internal stress in a specimen and the shape of the impact area. Test specimens were loaded by a force corresponding to the stress in specimen 0%, 10%, 20%, 30%, and 50% from the expected compressive strength. Rebound numbers of the unloaded test specimens were significantly lower than those of the loaded specimens. Therefore, calibration relations and/or correction coefficients processed by measurements of unloaded specimens can be assessed as unsuitable. To process calibration relations, we recommend exerting internal stress in amounts of 15% to 20% of the expected compressive strength of the tested HSC samples. During the determination of the effect of the shape of the test area on the cylindrical test specimen, it was assumed that the rebound numbers on the plane and the round test area would be the same. However, the test results revealed that the rebound numbers in the differently shaped test areas were different. For Schmidt impact hammer type N, the rebound numbers in the round test area were lower by 0.7 units on average, and for Schmidt impact hammer type L, the rebound numbers in the round test area were lower by 1.7 units on average compared to the plane test area rebound numbers.

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Section: Test Specimen Shapementioning

confidence: 99%

Rebound Hammer Tests of High-Strength Concrete: Effects of Internal Stress and the Shape of the Impact Area of the Test Specimens on the Measurement Results

Bodnárová¹,

Brožovský²

2019

Period. Polytech. Civil Eng.

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“…It was shown that the disagreement between "true" strengths and estimated strength can vary, because of: (a) some well-known driving factors defining the strategy (number of cores, repeatability of the measurements), (b) additional variables (i.e. like the fact that core locations are predefined or depend on information delivered by NDT), (c) chance (the same strategy repeated several times on the same structure will not lead to exactly the same results, for several reasons, including the measurement errors) [18], synthetic simulations which enabled to compare different strategies and to quantify the role of all most relevant driving factors [19], the shared analysis of real datasets which had been provided by experts.…”

Section: Recent Research Progress and Rilem Tc 249-isc Workmentioning

confidence: 99%

“…When some attention is paid to what happens during the full process, it is easy to understand that uncertainty (or errors) can impact the process at many stages. Significant research efforts have been recently devoted for a more systematic analysis of all the degrees of freedom of the non-destructive investigation and assessment process [18,[20][21].…”

Section: Recent Research Progress and Rilem Tc 249-isc Workmentioning

confidence: 99%

Reliable non-destructive strength assessment in existing structures: myth or reality?

Breysse

Balayssac

2019

RILEM Tech Lett

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The non-destructive assessment of concrete strength in existing structures is a complex issue which has been analyzed by a recently closed RILEM committee (TC 249-ISC) whose Guidelines and Recommendations are to be released soon. This committee has considered the state of practice, the yet existing standards and most recent innovative research results, in order to write recommendations that would improve the reliability of strength assessment with non-destructive techniques (NDT). These recommendations are based on a paradigm change: the challenge is not that of finding the true local strength, but that of estimating its value with a controlled tolerance interval and a limited risk of being wrong. Three levels of requirements are defined which correspond to different tolerance intervals on the assessed parameters and to a different amount of resources devoted to the investigation. While most of research has been devoted until now to the identification of relevant conversion models between NDT test results and strength, we have shown that the priority had to be put on other items, including the assessment of the NDT test results repeatability, the relevant definition of core locations and the checking of the final predictive error. This paper briefly describes the main innovations included in these recommendations.

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“…When determining the strength of the concrete "in situ" as indicated by Balayssac et al, 14 the combination of NDT methods is currently considered one of the most important techniques to improve the quality of diagnosis of concrete structures. However, according to Breysse et al, 15 there are no rules that establish the relationships among the amount of NDT information, the evaluation methodology, the processing of the results, and the precision in the strength concrete estimations. This is not the case as to the determination of strength by means of core drilled from the structure as it is strictly defined in the mentioned standards, referring to the quantity of cores, the diameter, correction factors, and humidity status.…”

Section: Coresmentioning

confidence: 99%

Variations of in situ concrete strength by European Standard and American Code

Gavilán

Filho

2017

Structural Concrete

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Europe and United States exert a worldwide influence in the field of concrete control, proof of this is that many countries adopt their regulations, due to lack of own regulations. When there are problems with concrete strength, cores are used, and this situation usually involves two or more parties with different views on the proper interpretation of the core results. An experimental study was carried out, with five lots of prototypes concrete slabs of 20, 30, and 35 MPa specified strength, 210 cylinders of 10 × 20 cm, 296 cores of 10 cm diameter, and slenderness 2, as well as temperature and maturity control. Estimated strength of cores and cylinders was compared according to the criteria of European standards UNE‐EN 13791 and the American code ACI 318. Tests were performed at 3, 5, 7, and 28 days. It is concluded that the European and American regulations present similar results for concretes with specified strength between 30 and 35 MPa, whereas in the range of 16–30 MPa, the European standard is more rigorous than the American Code, being the latter more favorable to the concrete producer.

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Non destructive assessment of in situ concrete strength: comparison of approaches through an international benchmark

Cited by 34 publications

References 10 publications

Rebound Hammer Tests of High-Strength Concrete: Effects of Internal Stress and the Shape of the Impact Area of the Test Specimens on the Measurement Results

Rebound Hammer Tests of High-Strength Concrete: Effects of Internal Stress and the Shape of the Impact Area of the Test Specimens on the Measurement Results

Reliable non-destructive strength assessment in existing structures: myth or reality?

Variations of in situ concrete strength by European Standard and American Code

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