Advancing the Rebound Hammer Method: A New Concrete Test Hammer

Abstract

The concrete test hammer patented by Proceq’s Ernst O. Schmidt at the beginning of the 1950’s is without a doubt the most widely used NDT instrument worldwide for rapid assessment of the condition of a concrete structure. Despite this fact, the validity of the method remains a hotly debated topic amongst experts in the NDT field. This is largely due to two factors; (a) since the original Proceq patent expired, there has been a proliferation of imitations with widely varying quality. Some are good, others are poor and the unreliability of the poor quality instruments has damaged the method in general; (b) the validity of the method in its primary use, i.e. for uniformity testing, is undisputed; however, incorrect use of the hammer for estimating compressive strength, (i.e. blind reliance on the manufacturer’s conversion curves) is a major cause for concern amongst NDT experts. Furthermore, since its introduction, not much has been done to improve the test method itself. This paper describes how recent advances in rebound hammer technology together with extensive research into the various factors that influence the results can improve the rebound hammer method, providing users with more reliable results and reducing doubts concerning the viability of the method.