موضوع مقاله : Retrofitting and Durability Enhancement of Concrete Sewer Pipe Using Pozzolans نویسندگان : مصطفی رستمی ، محمدرضا سهرابی چکیده: Concrete is the most widely used construction material for sewer pipes. Sewage environment creates one of the most corrosive conditions for concrete. The produced hydrogen sulfide gas (H2S), as a result of intractions in the sewer pipe, in the presence of aerobic bacteria and humidity produces sulfuric acid. Sulphuric acid is neutralised by reacting with the hydration products of the concrete matrix to form gypsum and ettringite. Both produce have a larger volume than represented by the initial compounds, which results in cracking. Furthermore, the degraded material can be removed by the sewage flow, which accelerates the corrosion process. The less the cement content, the less the corrosion rate. So replacing the part of cement with pozzolan is the most common method of durability enhacement of concrete being exposed to acidic environment. In this paper first the method through which the acid attack the concrete and behavior mechanism of concrete are investigated, then the role of pozzolan as a part of cement on the durability enhacement of concrete is studied. In this research the concrete cubic specimens containing Besh Aghaj pozzolan, silica fume, and nano- SiO2 are immersed in the sulfuric acid solution with PH of 1. Determining the weight loss and reduction of compressive strength of specimens whithin time steps, the durability of each mixture is investigated.