This thesis investigates the development of sustainable bituminous mixtures for base course applications, with a specific focus on evaluating the influence of recycled plastic on mixture performance. The study aims to assess how the incorporation of recycled plastic affects the volumetric and mechanical behavior of base course mixtures and how these effects can be exploited to support an optimized mix design approach. The experimental campaign was designed to analyze bituminous mixtures characterized by different recycled plastic contents and varying bitumen dosages. Volumetric and mechanical analyses were carried out to identify performance trends and to evaluate the role of recycled plastic within the mixture, supporting the definition of suitable mix design parameters for base course applications.