Currently, most of roads layed on concrete as construction base. But there is still much concrete which has damage or disability, one of which is voids. Voids are damage to the concrete in the form of a fairly deep hole. These voids if left unchecked will undermine structural concrete and will lead to other damage such as corrosion of iron contained in the concrete foundation. Voids occur on the inside of the concrete that is not easily detected. Ground Penetrating Radar (GPR) is a radar system which has capability to detect objects below the surface of the ground. GPRMax is a simulation software that has capability to modelling GPR system which the soil medium can be replace to concrete by changing it to different relative permittivity value. In this research, tests were carried out to detect voids in concrete utilizing simulations using GPRMax software. The results of this study produce an analysis of the signal reconstruction in the simulation that is the identification of the signal produced in the A-Scan process and identification of the depth level and position of voids for the B-Scan.