ABSTRACT
This chapter describes the theoretical and empirical based concepts as well as the history of development of combined nondestructive test methods for hardened concrete.
Of a number of purely nondestructive tests, the rebound (Schmidt) hammer and the ultrasonic pulse velocity combinations are the most commonly used. In the majority of cases, the need for in situ concrete strength evaluation arises as a result of suspect quality of concrete. By developing a prior correlation for a range of concrete grades and types, having only the source of coarse aggregate and a broad age group in common, it is possible to obtain good indication of the in situ strength of concrete, expressed as the value of a test result of a standard laboratory compressive specimen.
