Papers »

Micro-macro insights to failure of cementitious materials using granular micromechanics model

Macroscopic behavior of materials is highly dependent on their microstructure. Thus modeling a material without considering the specific microstructure, as it is done in traditional continuum mechanics, invariably leads to neglect of certain characteristic features. In the method of granular micromechanics the material’s macroscopic behavior is defined as the integration of the behavior of particle interactions, whereby material’s microstructure and the corresponding micromechanical characteristics are inherently included in the macroscopic behavior. A thermodynamically consistent granular micromechanics model suitable for cementitious materials has been developed which captures many features of their macroscopic and microscopic behavior. Inter-particle constitutive equations are defined so that they ensure compressive-tensile asymmetry. In the tangential direction, the forces are defined as functions of the tangential displacements and the mean pressures thus incorporating the effects of confinement on shear behavior and shear failure. Normal force components between the particles are also defined as functions of mean stress thus modeling the effects of confinement. In this presentation, the focus is set upon the failure of cementitious materials. From macroscopic view-point, three stages in failure are recognized, namely material instability (or stress uncontrollability), diffuse failure, and localized failure [1]. A detailed investigation of these failure modes has been performed under different multi-axial loading conditions, including: uniaxial, biaxial, and triaxial loading; volume control tests; multi-axial stress paths; and multi-axial strain path tests. Considering the nonlinear nature of the local constitutive equations and the anisotropy that these loading will induce on the material, all different loading scenarios will lead to different failure states and different failure types. Furthermore, the microscopic (grain-scale) origin of the macro-scale failure has been investigated to understand the micro-macro relationships in cementitious materials.
[1] Misra, A., and Poorsolhjouy, P. (2014) “Micro-macro scale instability in 2D regular granular assemblies,” .Continuum Mechanics and Thermodynamics, DOI 10.1007/s00161-013-0330-9

Author(s):

Payam Poorsolhjouy    
University of Kansas
United States

Anil Misra    
University of Kansas
United States