This research is dedicated to the estimation of the effective elastic modulus of polymer concrete by a new micromechanical model. The capability of the equivalent inclusion methods have been proved by numerous researches. The Mori-Tanaka (M-T) model is the most used homogenization scheme for two-phase composite materials. The M-T model provides good estimates of the stiffness tensor for two-phase composites with low to moderate volume fraction of inclusions. However, when the volume fraction of reinforcing phase is high, M-T model is unable to predict the stiffness tensor accurately. The major disadvantage of M-T model is that when volume fraction is high, in the associated isolated inclusion medium (AIIM), the properties of the reinforcing phase does not affect the matrix properties. The idea of the proposed model is that in high volume fraction of the associated isolated inclusion medium, the matrix phase must be affected by the reinforcing phase properties. In order to evaluate this model, twelve components with two different compositions were manufactured and tested. Also, the results from other researches were used to evaluate this model. The validation of the proposed model with the experimental data and results by other researchers shows the remarkable predictive capability of this model.