The application of an ultrasonic shear wave reflection method for nondestructive testing of cement-based materials at early ages

This book introduces an ultrasonic wave reflection method that measures the reflection loss of high-frequency shear waves at the interface of a steel plate and hydrating cementations materials. The reported investigations are devoted to the fundamental relationships among evolving microstructure, mechanical properties, and reflection loss. A wide range of material properties of different cement pastes, mortars, and concretes was evaluated by starting from phenomenological parameters, such as setting, and then moving to defined physical and physico-chemical properties, such as elastic moduli, degree of hydration, and porosity. To complement the experimental work, two numerical models - HYMOSTRUC3D and CEMHYD3D - for simulating the cement hydration process were employed. The investigations have shown that the measured reflection loss is closely related to setting, compressive strength, dynamic shear modulus, degree of hydration, gel-space ratio, and parameters describing the connectivity of the hydrating cement particles. The obtained relationships were used to develop a constitutive model that allows the determination of the mortar compressive strength from the measured reflection loss only.