This work aims to introduce a methodology for the determination of the effective properties of random heterogeneous materials. Specifically, focus of this study are the effective properties of two phase porous material containing spherical voids which are investigated both experimentally and numerically. To this end, three-dimensional porous structures, with non-overlapping porosity, are first generated by means of a random sequential algorithm. Numerical simulations are conducted on a representative volume element, whose size is first determined. Specimens are fabricated by 3D-printing of the computer-generated microstructures and tested under uniaxial loading. Good agreement of Young modulus data is found, in the case of spherical monodisperse porosity.