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 s tudying the increase in the propagation velocity of ultrasonic waves t ransmitted through a sample. In the case of a quick setting binder, th is method proves unsatisfactory. Concrete setting is modelled by disso ciating the chemical kinetics related to the volume transformations fr om those related to the surface transformations. Calculations show tha t the latter, and hence the percolation phenomenon, are prevalent in w ave propagation and concrete setting. As a result we assume that concr ete acts as a time-varying spectral filter. We are developing tests an d software to show that the energy and the frequency spectrum of the t ransmitted ultrasonic signal makes it possible to analyse the setting process and determine the setting time.