MARDOBET ash-slag mixture aggregate with the grain size of 0-20 mm, produced by the Raw Materials Recycling Plant Madrohut Sp. z o.o. [Ltd.]. The study aimed at the determination of the shear strength and bearing ratio of the aggregate depending on conditions, moreover, linear swelling was determined at different loadings of the sample. The shear strength tests were conducted in a direct shear apparatus in a box of 10 × 10 and 12 × 12 cm cross section with intermediate frames forming 1.0 cm thick shear zone. The samples were formed at the optimum moisture content and the degree of compaction I_S = 0,97, and then sheared directly after forming and after 3-day water-soaking. Bearing ratio and swelling were determined in a cylinder of a volume of 2.1 dm³. The values of the angle of internal friction and cohesion and bearing ratio at the optimum moisture content were relatively high. Hydration caused a significant reduction in cohesion and bearing capacity, while they were still relatively high. The aggregate swelling was less than acceptable. Based on the obtained results, the possibility of using the aggregate to build road embankments was assessed.