Characterization of Portland cement concrete microstructure using the scanning acoustic microscope

The scanning acoustic microscope has been applied to investigate several as pects of Portland cement concrete microstructure. This method uses ultrasou nd to image the local impedance at each point of a material. The impedance image highlights microstructural features that are difficult to observe wit h other imaging techniques. The topics investigated so far include the infl uence of aggregate composition on the development of the cement paste-aggre gate interface, the nature of interfacial transition zone, and ettringite f ormation. Several types of gels have been observed, and these can be classi fied by their characteristic impedance values. Future work includes quantif ication of impedance values by first arrival times and the identification o f Portland cement concrete phases by ultrasonic impedance spectroscopy. Pub lished by Elsevier Science Ltd.