Micro-scale X-ray computed tomography images of UHPFRC are used to construct finite element models for prediction of elastic properties using a two-step homogenization approach. In the first step, the mortar matrix with a large number of small voids is homogenized, and in the second the fewer large voids and steel fibres are modelled with the homogenised matrix. This leads to significant reduction in computational costs over one-step approaches. The results are compared favourably with experimental data. The effects of RVE size are also studied.