To achieve a satisfactory level of safety and stability in the construction of structures in weak soils, one of the best solutions may be soil improvement, the recycling and reuse of construction and demolition materials results in the preservation of natural resources and the reduction of environmental pollution. Therefore, this experimental study proposes to evaluate the mechanical properties of soil for surface foundations incorporating recycled demolition material. The mechanical behavior of a clayey soil improved with recycled concrete from demolition (CRD) was analyzed by means of a series of compaction tests, unconfined compression of soil specimens and direct shear in mixtures with 10 %, 15 %, 20 % and 25 % CRD by weight. As a result, the highest compressive strength of the soil is obtained with 16.67 % CRD according to UCS tests; and an improvement in cohesion and friction angle for all CRD percentages. Thus, it can be demonstrated that CRD has a positive influence on the mechanical properties of a soil with clayey characteristics.