EFFECT OF TRANSITION ZONE ON ELASTIC STRESSES IN CONCRETE MATERIALS

Concrete or mortar has three phases, namely, aggregate, bulk paste, an d the transition zone. The transition zone is the weakest link in the composite system; its presence may considerably affect the overall ela stic moduli and the stress distributions in a concrete material. The t ransition zone has a relatively more porous structure compared with th at of bulk paste, and it may not be, perfectly bonded to the aggregate . This paper proposes a four-phase composite model for investigating t he elastic stress analysis of concretes materials. The analytical solu tions of a four-phase composite model subjected to uniaxial compressio n are presented in two dimensions (2D) and three dimensions (3D). Mode ling of imperfect shear interfacial bond in a four phase composite mod el is shown. The 3D and 2D uniaxial compression solutions are compared . The effect of an imperfect shear interfacial bond on the elastic mod uli and stress solutions is illustrated. A parametric study is carried out to study the sensitivity of the stress distributions in the trans ition zone due to different aggregate types and due to changes in the elastic moduli of the transition zone. It is shown that the elastic mo duli of the transition zone and its interfacial shear bond with the ag gregate could considerably affect the overall elastic moduli and stres s distributions in a cement composite.