Prediction of Self-Compacting Concrete homogeneity by ultrasonic velocity

To evaluate the filling capacity of self-compacting concrete SCC without segregation, a technique based on the ultrasonic velocity has been adapted in order to estimate homogeneity and quality of concrete at very young age.To monitor local change in ultrasonic velocity, the process consists of using a pair of transducers at different depths of the concrete. The aim of our experimental study was to establish the relationship between ultrasonic velocity measured by sensors of 50 mm diameter and of 54 kHz frequency, and homogeneity of fresh concrete. Measurements of wave propagation velocity are carried out every half an hour on a vertical channel whose dimensions (in mm) are 160 × 160 × 700. These measurements have been determined with three modes of transmission: direct, semi-direct and indirect. The different mixtures were prepared with the same Water/Binder ratio (W/B) of 0.28. The amount of binder is in the order of 520 kg/m3.Comparison between ultrasonic velocity and empirical tests such as sieve stability test, slump flow test, air content, and compressive strength, at 1 day, shows that the ultrasonic velocity can also be very useful to evaluate homogeneity and quality of fresh concrete.