Abstract: The deterioration mechanism of concrete materials with expanding serpentine aggregates subjected to fast neutron radiation (MeV>1.0) was investigated by numerical simulation. Considering the combined effects of temperature and aggregate radiation-induced volumetric expansion (RIVE) on the mechanical behavior and the residual elasticity of concrete, a two-stage numerical model was established at the mesoscopic scale. The residual elasticity of concrete was investigated numerically and validated by comparing with experimental data. Based on the numerical results, the analytical formulas of concrete swelling and the residual elasticities were proposed. The 3D numerical approach can provide an effective tool for assessing the combined effect of temperature and RIVE in the aggregates on the mechanical behavior and the residual elasticity of concrete with application to fast neutron radiation, and for revealing the deterioration mechanism of concrete materials with expanding aggregates. The proposed model serves as a first attempt and provides a theoretical benchmark and can be potentially applied for the life extension evaluation of aging concrete materials.