Abstract: Despite small thickness, the interfacial transition zone (ITZ) between aggregate and cement paste has remarkable influence on the elastic modulus of concrete with its strong inhomogeneity in microstructure. In consideration of the inhomogeneity of ITZ, a multi-phase prediction model for the elastic modulus of concrete was proposed based on the meso-inclusion theory, in which the matrix phase containing voids and cement pastes was considered as the equivalent matrix, and the inclusion phase consisting of aggregate and inhomogeneous ITZ was considered as the spherical equivalent particles with different diameters, and finally an equivalent homogeneous concrete consisting of equivalent matrix and equivalent particles was formed. The predicted values of elastic modulus agreed well with Stock’s experimental results. In addition, quantitative analysis unveiled that the inhomogeneity of ITZ had a profound influence on elastic modulus of concrete: the higher inhomogeneity level of ITZ, the lower of elastic modulus. The elastic modulus of concrete also declined with the increases of ITZ thickness and the porosity of cement paste, while increased with the volume fraction of aggregates.

Key words: concrete, elastic modulus, interfacial transition zone, inhomogeneity, meso-inclusion theory