Role of Expansion on Mechanical Behavior of Concrete

The collective experimental evidence from standard uniaxial, biaxial, and triaxial tests of plain concrete is examined to identify the essential governing state variables for the benefit of three-dimensional constitutive modeling of the material. It is shown that the volumetric expansion that develops in mechanically loaded concrete due to progressive microcracking is an important measure of the extent of damage in the material microstructure, and can be used to consistently estimate the changes effected on the resistance of concrete as damage accumulates. Within this framework, the degree of restraint against expansion, such as is provided by arbitrary boundary conditions, can be used to completely determine the residual strength and deformability of concrete under these conditions. These concepts provide the tools for the development of a simple but general constitutive model for concrete and offer an opportunity for unification of the existing interpretations of various aspects of the observed mechanical response of concrete. Example problems are included demonstrating that with a limited number of physical variables it is possible to reproduce the sensitivities of an array of benchmark experiments.