A. Prof. Jianfeng Wang（王剑锋副教授）
City University of Hong Kong（香港城市大学）
An advanced study on sand particle morphology using Nano-focus X-ray CT and mathematical modeling
This presentation reviews the recent progress in nano-focus X-ray CT characterization of particle breakage behavior of sands and mathematical modeling of 3D morphology of sand particles. The novelty of the study stems from the pioneering application of the state-of-the-art synchrotron CT technology and mathematical methods to the exploration of the fracture behavior of sand particles at the micron and sub-micron scales, the accurate reconstruction and reassembling of 3D sand particle morphology, the assessment of the effects of particle microstructure and micro-morphology on the fracture behavior. The presentation first introduces the nano-focus X-ray CT technique and describes its application to the exploration of particle breakage behavior in typical element soil tests, e.g., single particle crushing test, oedometer test and triaxial test. Typical results from the CT study are presented. Then the spherical harmonic analysis (SHA) method, the image matching techniques and their application to the reconstruction and reassembling of 3D sand particle morphology are presented and discussed.
Prof. Fangyuan Li（李方元教授）
Tongji University（同济大学）
Study on the Mechanical Properties and Application of Directionally Distributed Steel Fibre Reinforced Concrete
The fibre utilization efficiency of directionally distributed fibre-reinforced concrete is better than that of randomly distributed fibre. Directionally distributed steel fibre-reinforced concrete (SFRC) has been proposed as a novel concrete because of its high tensile strength and crack resistance in specific directions. However, controlling the fibre direction is difficult, which limits its applications. In this report, a method in which fibres were artificially directed was used to simulate the feasibility of orienting fibres during 3D concrete printing. Based on artificially directed steel fibre-reinforced concrete specimens, the orientation characteristics of directional fibre-reinforced concrete specimens were studied. The differences between the gravity and the boundary effects in ordinary fibre-reinforced concrete and artificially directed fibre-reinforced concrete were compared. This result demonstrated the feasibility of manually orienting the fibres in steel fibre-reinforced concrete in layer-by-layer casting.
Based on the existing studies of the effect of the fibre direction on the mechanical properties of fibre-reinforced concrete (FRC), the author performed further studies of the mechanical properties of directionally distributed SFRC by conducting split tensile and bending tests. The split tensile strength of the directionally distributed FRC clearly exhibited anisotropy. The split tensile strength perpendicular to the fibre direction was much higher than that parallel to the fibre direction. The split tensile strength perpendicular to the fibre direction was almost twice the tensile strength of plain concrete. The flexural performance of directionally distributed FRC in the fibre direction significantly improved compared to that of randomly distributed FRC.
Directionally distributed Steel Fibre-Reinforced Concrete (SFRC) cannot be widely applied due to the limitations of its construction technology, which also hinder research on its mechanical properties. With the development of new construction technologies such as 3D printing, directionally distributed SFRC has found new developmental opportunities. In this paper, we tested, compared and analysed the basic mechanical properties of ordinary concrete, randomly distributed SFRC and directionally distributed SFRC. We monitored the difference between the damage patterns parallel and perpendicular to the direction of the steel fibres in directionally distributed SFRC.
The test results can be utilized in subsequent concrete designs. The conclusions reached in this paper provide comprehensive mechanical design parameters for the application of directionally distributed FRC.
A. Prof. Xinzhi Zheng（郑新志副教授）
Henan Polytechnic University（河南理工大学）
A. Prof. Christian Gänshirt
Xi'an Jiaotong-Liverpool University
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