When the interfacial transition zone (ITZ) is treated as a separate phase, the ITZ volume fraction plays an essential role in determining the physico-mechanical properties of concrete. The intention of the present paper is to develop a numerical algorithm for the ITZ volume fraction in concrete with spheroidal aggregate particles. By applying a contact function for two spheroidal aggregate particles and introducing periodic boundary conditions, the distribution of spheroidal aggregate particles with various sizes within a cubic element is implemented. The Monte Carlo method is then adopted to evaluate the ITZ volume fraction. After the validity of the developed numerical algorithm is verified with the analytical solution for the ITZ volume fraction in concrete with spherical aggregate particles, the effects of various factors that affect the ITZ volume fraction are evaluated through sensitivity analysis.It is found that the ITZ volume fraction increases with the increase of the ITZ thickness, but decreases with the increase of the maximum aggregate diameter and the aspect ratio of spheroidal aggregate particles. It is also found that the aggregate gradation has a significant influence on the ITZ volume fraction. The paper concludes that the numerical algorithm developed in the paper can predict the ITZ volume fraction with reasonable accuracy.
The variation of the dynamic modulus of a model electrorheological fluid with strain amplitude is shown to closely resemble that of traditional physical gels. Comparison of the in-phase stress component in each system indicates that the material strength of electrorheological fluids in shear is limited by the small strain amplitude to structural failure. An anisotropic network model is proposed for electrorheological fluids, in which the primary structure consists of chains of particles spanning the electrode gap along the field direction, while many-body interactions form a secondary structure of short chains tilted with respect to the field direction and interconnecting the primary chains. A geometrical argument shows that the tensile strain in the secondary structure can be an order of magnitude larger than that in the primary chains. This nonuniform strain distribution poses an inherent structural limitation on the shear material strength of electrorheological fluids.
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