A three-layer built-in analytical modeling of concrete

Abstract

It has been accepted in recent years that concrete can be treated as a three-phase composite, consisting of a cement mortar continuous phase, a coarse aggregate dispersed phase, and interface transition zone (ITZ)– an interphase between cement mortar and coarse aggregates. A large number of experiments have been conducted to investigate the effect of every phase on the mechanical properties of concrete; however, the analytical modeling studies have not been conducted as extensively as experimental studies have. In this paper, a three-layer built-in model was developed by assuming coarse aggregates as spheres and embedding a spherical coarse aggregate coated with an ITZ-like interphase and cement mortar layer with uniform thickness into equivalent concrete media. The preliminary calculation results show that, for the three-phase concrete, each phase has several effective factors for the improvement of the mechanical properties of concrete. For overall evaluations, the effective factors are: 1) reducing the elastic modulus of cement mortar and ITZ-like interphase and increasing the elastic modulus of coarse aggregates, 2) decreasing the coefficient of thermal expansion of each phase, 3) enhancing the tensile strength of cement mortar and reinforcing the deformability of ITZ-like interphase, 4) reducing the volume fraction of cement mortar and increasing the concentration of ITZ-like interphase and coarse aggregates phase, 5) decreasing the maximum grain size of coarse aggregates, and 6) adopting open-graded coarse aggregates.