Extensive statistical analysis of the variability of concrete rebound hardness based on a large database of 60 years experience

• Repeatability of rebound hammer test depends on type of cement, w/c-ratio and age.
• Repeatability parameter distributions have positive skewness for rebound hammer test.
• Rebound index coefficient of variation cannot estimate that of compressive strength.
• Repeatability and precision claims (ACI 228.1R-03; ASTM C 805) need reconsideration.
• Basic curve and assessment method of EN 13791 need reconsideration for rebound test.

Non-destructive testing methods for concrete structures require statistical validation of reliability model parameters. Present paper studies a comprehensive database of several thousand test locations for the better understanding of the statistical characteristics of rebound hardness of concrete and highlights that several gaps are found both in current technical literature and standardisation. Detailed evaluation is provided on repeatability and influencing parameters. Results of statistical analyses are presented for the within-test standard deviation, coefficient of variation, range and studentized range of rebound indices. Indications for the reconsideration of particular statements in the technical literature and standards are given.