Physico-mechanical properties of mortars based on the addition of dune sand powder (DSP) and the recycled fines (RF) using the mixture design modelling approach were investigated. This experimental program aims to provide solutions and answers on the use of DSP and the recycled concrete waste in the form of fines for manufacture of the mortar having good properties. For this purpose, both additions are added by substitution of cement up to 25%. Through the results obtained, we have noticed the interest of modelling the response studied by a polynomial which is then able to calculate all the responses of the field of study without being obliged to make all the experiments. The obtained results showed that the introduction of DSP and RF in cement (by substitution) leads to a considerable improvement of mechanical strengths. The dosages of the three factors have optimum values (respectively around 66.66% of cement, 33.33% of DSP, 0% of RF in substituted volume of 112.5kg of cement) for which the compressive strength (Cs) reaches a maximum value. Cs increases when the percentage of additions increases till an optimum (8.33% DSP, 8.33% RF), then decreases for larger percentages. One can observe that after 28days, highest flexural strengths are that of mortars M7 and M9, with an optimum effect for the mortar M7. In addition, the modelling of the workability shows that the presence of DSP improves the workability of the mortars in the fresh state. Recycled fines have a negative effect on the flow time.