Sand occupies a great proportion of the cementitious matrix product and in particular mortars. Hence, the study of fine aggregates used for concrete and mortar in general, deserves to be objects of research including sand which has always been considered as inert material, the role of which is related exclusively to its physical appearance in the development of mechanical responses. The main objective of the present experimental research work is to study the effect of the type and rate of substitution of mineral additions pozzolan and blast furnace slag of a natural sand fine fraction (sieve diameter less than 0.16 mm) on the mechanical responses and durability. The study here in focused on these particular characteristics of formulated mortars to be assessed to evaluate mortars performances. Mixtures were prepared (mixed sands) by varying the dosage of the two factors related to additions (Slag and Pozzolan) introduced separately from 0% to 10% at 2, 5% step increment. The substitution of the finest fraction of the particle size composition of the natural sand as well as the ordinary Portland cement (CEM I / 42.5) were used for studied mortars. The results obtained show a significant improvement of the mechanical properties for the mortars based on the new activated sand. With regard to durability tests of HCl and H2SO4 acids chemical attacks, the substitution of the quartz by active mineral additions in the sand-size skeleton allows a reduction in resistance loss of up to 50% and a mass gain up to 75%.