In Morocco, waste management is an important subject. According to many proposals, the recycling of construction and demolition waste (CDW) in the form of aggregates replacing natural aggregates for concrete is a solution that merits evaluation. In this study, three samples of concrete are tested, two with different percentages of recycled aggregates. These properties are compared to the concrete with natural aggregates. Concrete is realized and tested in thermal conductivity (cylindrical specimens). We consider quantities of recycled aggregates (0%, 10% and 20%) in different temperatures (20°, 30°, 40° and 50°C). Numerical modeling with FORTRAN program was proposed for comparing between experimental and numerical results. It is shown that the use of recycled aggregate as replacement for natural aggregate in concrete decreases the thermal conductivity. We also see that the value of the thermal conductivity reduces with the elevation of the temperature of the ambient air 20 degrees up to 50 degrees for the three samples normal concrete and concrete with recycled aggregate. For the three samples, the numerical and experimental results were in good agreement. The following conclusion can be drawn from this work: according to the thermal properties, the recycled aggregate concrete will be used in the same operations as normal concrete.