Torsional waveguide sensor system for monitoring the setting and hardening of concrete

A torsional waveguide sensor system that monitors the setting and hardening of early-age cementitious materials during the first twenty-four hours of hydration is presented. The fundamental torsional wave mode is transmitted on the free end of a cylindrical steel rod partially embedded in the concrete and then the reflected signals are received. The method monitors both the reflection from the end of the rod embedded in concrete and the reflection from the location where the waveguide pierces the concrete. The waveguide sensor has the advantage of being able to operate from one side of the specimen, often a necessity for field measurements. The method has previously been shown to be able to monitor the development of the mechanical properties of various mortar mixtures (for example, different water-cement ratios, presence of chemical and mineral admixtures). In this technical note, preliminary results show that the method can be extended to concrete mixtures.