Materials and Structures

, 52:71 | Cite as

Recommendation of RILEM TC249-ISC on non destructive in situ strength assessment of concrete

  • Denys BreysseEmail author
  • Jean-Paul Balayssac
  • Samuele Biondi
  • David Corbett
  • Arlindo Goncalves
  • Michael Grantham
  • Vincenza A. M. Luprano
  • Angelo Masi
  • Andre Valente Monteiro
  • Zoubir Mehdi Sbartai
RILEM Technical Committee


This recommendation is written to improve the assessment of the in situ. Compressive strength of concrete in existing structures by combining core strength values and non-destructive measurements. Both average strength and its scatter are considered. Deriving a characteristic strength from the assessment results is not considered here. The recommendation applies for most common techniques (ultrasonic pulse velocity, rebound hammer, pull-out) but also for less common techniques (penetration test, etc.). The recommendation does not apply to situations in which no core has been taken from the existing structure and is limited to situations where NDT is combined with cores. The recommendation introduces the concept of Estimation Quality Level, corresponding to the target of assessment, and which is put in relation with the means and strategy developed for assessing concrete. The text details all steps that must be followed from the data gathering to the checking of the quality of the final estimations. For more clarity, an illustrative example is described for each step of the assessment process.


Concrete strength Model calibration Non-destructive techniques In-situ investigation Rebound hammer Strength assessment Ultrasonic pulse velocity 

List of symbols

a, b

Conversion model parameters


Calibration factor


Calibration factor (scaling calibration)


Coefficient of variation (= standard deviation/average value)


Coefficient of variation of test results (for test result precision)


Calibration factor (shift calibration)


Estimation quality level


Index for estimated values


Concrete compressive strength


Estimated concrete compressive strength


Estimated and calibrated concrete compressive strength


Prior estimated concrete compressive strength


Index for measured values (from 1 to NTL for NDT test results, from 1 to Nc for core strength) or assessed values


Index for conversion model parameters (from 1 to Npar)


Index for NDT techniques


Conversion model (fc,est = M (Tr))


Index designating the mean value of measured (test results, core strengths) or estimated properties (strength)


Number of cores


Non-destructive testing


Number of parameters of the conversion model


Number of readings (repetitions of individual measurements) in order to derive a test result


Number of repetitions of a test in order to derive the test repeatability


Number of test locations (= number of NDT results)


Value of the j-th conversion model parameter


Determination coefficient


Rebound hammer (for technique or test result)


Root mean square error


Fitting root mean square error, estimated on the identification set


Prediction root mean square error, estimated when the conversion model is applied to new data


Standard deviation


Standard deviation of test results (for test result precision)


Test location


Test region


Test result


Value of the i-th NDT test result (when a single NDT is used)


Value of the i-th test result of the k-th NDT method (when several NDT are combined)


Test result precision


Ultrasonic pulse velocity (for technique or test result)



The authors of this RILEM TC 249-ISC gratefully acknowledge all contributors who are cited above and do not appear as full authors of the recommendation for administrative reasons.

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.


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Copyright information

© RILEM 2019

Authors and Affiliations

  • Denys Breysse
    • 1
    Email author
  • Jean-Paul Balayssac
    • 2
  • Samuele Biondi
    • 3
  • David Corbett
    • 4
  • Arlindo Goncalves
    • 5
  • Michael Grantham
    • 6
    • 7
  • Vincenza A. M. Luprano
    • 8
  • Angelo Masi
    • 9
  • Andre Valente Monteiro
    • 5
  • Zoubir Mehdi Sbartai
    • 1
  1. 1.University Bordeaux, I2M-UMR CNRS 5295TalenceFrance
  2. 2.INSA ToulouseLMDCToulouseFrance
  3. 3.University Chieti-PescaraChietiItaly
  4. 4.ProceqSchwerzenbachSwitzerland
  5. 5.LNECLisbonPortugal
  6. 6.Leeds UniversityLeedsUK
  7. 7.Sandberg LLPLondonUK
  8. 8.ENEABrindisiItaly
  9. 9.University BasilicataPotenzaItaly

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