EVALUATION FOR DISTRIBUTION OF MATERIAL PROPERTIES IN RCD CORE SAMPLES BY X-RAY CT METHOD

Abstract

On the RCD (roller-compacted dam-concrete) method, very stiff concrete is compacted by vibration rollers after spread in either 75cm or 100cm in thickness. In this method, compressive strengths of upper part and lower part in a lift are sometimes observed to be different, namely strength of upper part is lower than that of lower parts. In this study, compressive strength test and ultrasonic pulse velocity test were carried out for the core samples drilled from the RCD trial embankment. At the same time, X-ray CT (Computed Tomography) method was applied to the core samples to investigate the vertical distribution of material properties such as coarse aggregate ratio, void ratio and mortar density. It is shown that coarse aggregate ratio is uniformly distributed in vertical direction, but voids and average mortar CT value are different between upper part and lower part in the core samples. Furthermore, analyzing the CT images, voids are found on the boundary between coarse aggregate and mortar in upper part. Then it is considered that those voids mainly influence the heterogeneity of the compressive strength of the RCD core samples.