In the environmental field, the valorization of plastic waste has become a primary issue. The approach is achievable by developing ways to use this waste as an alternative to make new building materials. Their reuse can promote the elimination of these wastes and the protection of the environment, as well as the progress in sustainable development. The main objective of this study is to develop the functionality of the thermal properties of concrete by incorporating HDPE waste in an ecological concrete mix. This concrete is characterized by the partial replacement of the sand by HDPE (5%, 10%, 15%, 20%, 25% and 30%). For this purpose, experimental studies were made to determine the thermophysical parameters including thermal conductivity and volumetric specific heat at an ambient temperature of 24°C. The results obtained show that the density in the dry state has decreased by a rate of 13%. This resulted a decrease in thermal conductivity, specific heat and thermal diffusivity by 33.91%, 25.45% and 16.13%, respectively, compared to the reference concrete. This method has improved the thermal performance of a sustainable and environmental-friendly building material.