Cement is a strategic product in the civil engineering for the construction of reinforced concrete structures. But its production generates around 5% of toxic gases such as CO2 responsible for the ecological environmental degradation of the planet; moreover the cement industry is a consumer of non-renewable energy sector. Using natural additions in cement is a solution to reduce the CO2 gas and the cost of production. The purpose of this work is the study of a sustainable building material: natural pozzolan (PN) of Beni Saf (Algeria) which is incorporated into mortars exposed to an attack of 5% sulfuric acid. The loss of mass, monitoring the pH of each solution over time as well as the dimensions of the specimens are the different tests to study durability of mortars made up 0, 10, 20 and 30% pozzolan. The results show that the natural pozzolan improves mortars resistance in acidic environment.