Paper by SZTUKIEWICZ RYDZEWSKI from ISCR 7th 1994 Vienna Austria
To determine the concrete strength of a road surface the authors of this paper have used an ultrasonic method. In this method, longitudinal waves are directed to a concrete slab by means of transducers applied to the upper surface of the slab. If the propagation time and the distance between the transducers are given, it is possible to determine the ultrasonic characteristics as the velocity propagation of the longitudinal wave and the velocity wave change coefficient. The relationships between the concrete strength, the homogenity and the ultrasonic characteristics have been established. The method also allows for observing the changes taking place in the concrete slab during a certain timelap. The authors have observed those changes by means of ultrasonic characteristics. The aim of this paper is to present the results of the observation of ultrasonic characteristics in the process of concrete hardening as well as during its 8 years under traffic.