LAUSR

Abstract Non-destructive testing (NDT) has a vital role in finding surface hardness of concrete members. B-Proceq curve can calculate the concrete strength by providing statistical correlations between the destructive and the non-destructive strength. The regression curve based on the laboratory test may be valid within their implementation boundaries. It is not feasible to extend the validity of these curves to the in-situ test. Factors influencing such curves include the w/c ratio, carbonation effect, exposure to fire, compaction, curing condition, and type of the cement used in concrete, etc. More than 65 years of research data with the Schmidt rebound hammer is used for evaluation. The Authors also addressed the effect of each influencing factor on the performance of the rebound hammer and suggested amendment in the B-Proceq curve. Various factors affect the rebound index significantly and hence their consideration while conducting a rebound test is necessary. The large deviation of curves raised a crucial question of whether the rebound hammer is effective or not in estimating the concrete strength.