SETTING TIME STUDY OF ROLLER COMPACTED CONCRETE BY SPECTRAL-ANALYSIS OF TRANSMITTED ULTRASONIC SIGNALS

The setting time of roller compacted concrete (RCC) is determined by studying the increase in the propagation velocity of ultrasonic waves transmitted through a sample. In the case of a quick setting binder, this method proves unsatisfactory. Concrete setting is modelled by dissociating the chemical kinetics related to the volume transformations from those related to the surface transformations. Calculations show that the latter, and hence the percolation phenomenon, are prevalent in wave propagation and concrete setting. As a result we assume that concrete acts as a time-varying spectral filter. We are developing tests and software to show that the energy and the frequency spectrum of the transmitted ultrasonic signal makes it possible to analyse the setting process and determine the setting time.