Builders in our country are not familiar with the practice of using mineral additives, as cement substitutes, in cast-in-place and in ready-mix concretes. It thus seemed important to study and evaluate the impact of these additives, as cement substitutes, on the properties of set concrete. The mineral additive used is natural pozzolan found in large quantities in Western Algeria (Béni-Saf); however, it must be beneficiated. To do so, we designed three pozzolan-based concretes (20, 25, and 30%). We measured compressive strengths at various times and produced a reference control concrete for comparison purposes.Key words: pozzolan, dosage, concrete, composition, substitution, compressive strength.[Journal translation]