The present work focuses on the investigation of the mechanical properties of the composite material composed of preliminary modified rubber crumb and a polymer binder. The modification of rubber crumb was realized by means of treatment with water or sulphuric acid, in order to change the degree of polymer crosslinking or to intensify adhesion interaction between rubber particles and polymer binder. The Shore C hardness, compressive stress at 10% deformation and compression modulus of elasticity, ultimate tensile strength and elongation at break of composite material, in correlation with its composition and adhesion between rubber and polymer binder were investigated. Obtained results show possibility of attaining significant changes in the mechanical properties of composite material by selected rubber crumb treatment methods, in correlation with the composite material composition. This gives additional opportunity for meaningful improvement of composite material production technology.