Resistance of two different types of concrete pipes used in sewer systems under sulfuric acid and sodium sulfate attacks

The behavior of two concrete used in sewer pipes was studied by immersion tests in acid and sulfate solutions at 25°c and 40°c,in order to study the influence of production method,cement and aggregate types used for each concrete. the gain of weight for concrete aged in na2so4 at 25°c which had been oven dried is explained by the absorption of solution into the empty pores of matrix. the delay in weight gain for concrete aged in na2so4 at 40°c is due to the fact that pores were initially filled with air,and the incoming solution had to compress/dissolve/diffuse air to allow the diffusion of solution into specimen. the mass loss for concrete aged in h2so4 at 25°c and 40°c is due to acid reacting with alkaline substances. the weight gain for concrete aged in 50g/l na2so4 at 25°c result from water that fills the cracks and a mass of water used to precipitate a hydrated phase. these results allowed to obtain that: centrifugation method with a low w/c ratio,gave a dense and less porous concrete,characterized by a rapid diffusion of solution,that can be attributed to the disappearance of finer element's concrete during centrifugation (remove with water),which will facilitate the diffusion of solution into concrete. portland cement with limestone and portland cement with fly ash,limestone and dolomite aggregates,which were used,are sensitive to acid attack. these results prove that concretes' behavior mainly depends on the production method,cement and aggregate types and w/c ratio.