Modeling and predicting the mechanical behavior of concrete under uniaxial loading

Nowadays concrete has become the most widely-employed construction material in civil engineering. But at present stage, not all internal factors’ effects on this material's axial and transverse mechanical behaviors have been comprehensively understood, and highly-accurate formulas to predict its mechanical properties are still lack. This prevents designers and engineers to well construct structural components, and also separates people to better know the failure mechanism and strength rule of other types of concrete materials (such as the recycled aggregate concrete and the recycled lump concrete). Considering such situations, a series of discrete element simulations were conducted in this study. In current works, concrete was at mesoscopic level modeled as composed by coarse aggregates, mortar and interfacial transition zones (ITZs). The influences of each constituted phase's attribution and content (including the shape, size, location, volume content and attribution of coarse aggregates, the mortar's water-to-cement ratio as well as the property of the ITZs) on the concrete's crack development process, failure pattern as well as longitudinal and lateral mechanical responses were analyzed carefully. The factors most important in determining concrete's tensile and compressive strengths together with elastic modulus were identified, and accurate expressions for relating concrete's uniaxial mechanical properties with the attributions of its components were also proposed. The present study showed that mesoscopic discrete element simulation is an ideal tool for expressing the concrete's the development of internal damages/cracks and understanding its lateral deformation features under uniaxial loadings. The compressive strength of concrete is primarily governed by the mortar's strength, the aggregate content and the bonding strength of aggregate-mortar ITZs, and its elastic modulus is notably affected by the mortar's modulus and the aggregate content, while the tensile strength is greatly influenced by the strengths of mortar and ITZs. Expressions are proposed which usefully predict concrete's properties based on its constituents, and they may be further extended to investigate the mechanical properties of other types of concrete.