Koji Otsuka

Fracture process zone in concrete tension specimen

Abstract Experiments were carried out with X-rays using contrast medium and three-dimensional (3D) Acoustic Emission (AE) techniques to investigate the behavior of the fracture process zone in concrete. The results show that, as the loading increases, a zone consisting of numerous microcracks accompanied by AE events develops ahead of the notch tip in the concrete compact tension specimen. The energy of each individual AE event was calculated and plotted on the (3D) map. The results obtained by the two methods were compared and related to provide a clear view of the fracture process zone of concrete.

Bond Cracking and Tension Stiffening Properties of a Deformed Bar Embedded in HPFRCC

A series of bond tests on a deformed bar embedded in high-performance fiber reinforced cement-based composites (HPFRCC) were carried out. Bond cracks around the reinforcing bar were observed by an X-ray technique and strain distribution along the bar was measured, too. Based on these experimental results, the mechanism to enhance the ductility of reinforced HPFRCC was discussed.