Rebound Hammer Test: An Investigation into Its Reliability in Applications on Concrete Structures

Abstract

The issue of concrete strength often arises in civil engineering practice, either due to quality control of new constructions or due to the assessment of existing structures. To this aim, one of the most widely spread techniques is the rebound hammer (Schmidt hammer) test, for which calibration is still related to the original Schmidt curve dating back to the early 50’s. In spite of the large amount of research work performed in the last decades, the uncertainties of the rebound test are still not clearly quantified and open to further insight. This paper presents and discusses a wide research campaign on laboratory specimens and on third-party specimens delivered to the Laboratory for Building Materials of the University of Genoa, Italy, for standard quality controls. While it is well known that moisture content, surface finishing, and concrete maturity strongly affect the test result, the effect of the stress state has not yet been studied and is found in this research to be a further parameter affecting the test reliability. The final outcome of all the uncertainties is variability in estimated concrete strength as large as ±70%; additionally, some issues are discussed on the intrinsic uncertainty of this test. As already demonstrated by many authors, the results of this research also show that a universal calibration curve to be used for any concrete, in any condition, conceptually does not exist.

Comparison of Nondestructive Testing Method for Strength Prediction of Asphalt Concrete Material

“…After 7 days the rebound hammer work more consistent due to surface hardness development in concrete. This finding is in good agreement with literature [14,30].…”

“…An excellent review of nondestructive testing method for concrete material could be found in work collected by ACI 228 report [12] and handbook on nondestructive testing of concrete [13]. Examples of these methods are surface hardness methods [14], penetration resistance method [15], pullout method, break-off method [16], maturity method, pull-off method, resonant frequency method, and ultrasound pulse velocity method [4][5]17]. But it has not been adopted by engineers and institutions specialized in developing standard specifications to determine the compressive strength of concrete [18][19].…”

“…The factors affecting RN could be classified according factors related concrete mix proportions such as aggregate type, water/cement ratio, admixtures, and cement type. Other factors classified according concrete conditions such as moisture content, curing condition and age, concrete maturity, and surface carbonation [14].…”

Experimental Study on Special Testing Strength Curve for Compressive Strength Evaluation by Rebound Method

“…Rebound method plays a vital role in not only the quality control of new concrete construction but also the strength evaluation of existing concrete structures [1]. e rebound hammer test is primarily used in common engineering practice among the nondestructive technique's procedures because of its simplicity, speed, and low equipment price [2][3][4][5]. Currently, the most widely used rebound hammers were developed by the Swiss scientist Ernst Schmidt [6,7].…”

“…Kumavat et al [11] considered that the regression models based on the laboratory test might be valid within their implementation boundaries for estimating the compressive strength of concrete. Brencich et al [4] suggested that the conception of a universal calibration curve for any concrete does not exist under any conditions. us, some research had been devoted to studying the special testing strength curve for regional engineering or special projects.…”