Non-destructive evaluation of eco-friendly cementitious materials by ultrasound (original) (raw)

Ultrasonic methods have been developed in the past to study properties of cement based materials in the fresh and hardening state. However, most of the methods only consider a certain type of ultrasonic waves. To derive elastic parameters of fresh concrete like the Poisson's ratio and elastic modules it is required to obtain shear waves as well as compressional waves. It is certainly much more difficult to establish a setup to transmit and record shear waves in a way that the onset of these slower waves (compared to compressional waves) can be detected as clear as necessary to calculate shear wave velocity values with the required accuracy. A test setup for testing cement paste with different ultrasonic waves is presented. Tests have been conducted that show reasonable ultrasonic compressional and shear wave transmission right after mixing. Thus ultrasound is found to be suited for the characterisation of paste mixtures and the determination of changes in the rheological properties already before setting. Test results from different cementitious mixes with a special focus on eco-pastes are presented. These eco-pastes show optimized packing density (using micro and eco fillers as replacement of Portland cement clinker).