Comparison of pulse-echo-methods for testing concrete

Pulse-echo methods (radar, impact-echo, ultrasonic impulse-echo) and simulation of wave propagation are applied for testing concrete specimens with metal ducts. The results of nondestructive testing of the same specimens by nine workgroups are described and compared. The research aims for the experiments are thickness measurement, location of a metal duct and of voided regions inside the duct. The results show the remarkable progress achieved in the past few years: the thickness and location of a duct could be measured for one specimen with great precision. In some cases voided regions in the duct could be located.