Backfill is a key element in the construction of soil-steel bridges. These types of bridges have been widely used for many years in transport infrastructures in North America, Europe and Australia. The design codes and calculation methods related to soil-steel bridges and culverts specify, among others, the requirements for backfill. The typical backfill should be well-granulated sands and well-compacted gravels of harsh, coarse, or round grains. However, over time and with new/modified uses for these structures, expectations for standard backfill are changing. Materials that contain a certain amount of recycled materials and at the same time have better properties than typical backfills, e.g., vibration damping, are increasingly sought after. It is anticipated that this development direction in infrastructure engineering can also be adopted for backfills used in soil-steel bridges. Therefore, as part of this study, the authors examined the behaviour of a soil-steel bridge model with backfill containing the addition of granulated rubber from end-of-life tires (gravel-rubber mix) under static loads. The tests were carried out in a specially constructed test box with a real bridge structure (a culvert made of corrugated sheets). The finite element method was then used to perform calculations on the bridge model. The analysed soil-steel bridge has the following dimensions: (i) 2.1 m span, (ii) 1.45 m height, (iii) 2.32 m length, (iv) 2.5 mm sheet thickness, and the wave profile is 68 × 13 mm. In addition, the steel box dimensions are 2.32 m × 4.34 m × 2.49 m (width × length × height). The results indicate that the gravel-rubber mix can be used in soil-steel bridges as an alternative to traditional backfill. The proposed backfill (gravel-rubber mix) will ensure the safe transfer of external loads. An additional benefit is the use of tire recycling, which is part of the sustainable development of the construction industry.