de Sousa Coutinho, A
Chief of the Building Materials Department, National Civil Engineering Laboratory, Ministry of Public Works, Avenida do Brasil, Lisboa,
This paper discusses three aspects of sulfate attack on concrete that are important in understanding the development of sulfate-resisting concretes. These are: the importance of a precipitated layer of reaction products at the surface of the concrete, the role of aggregate type in the formation of ettringite, and the importance of the alkalinity of the medium in which the ettringite is formed. It is shown that alumina of kaolinized feldspar react with sulfates in a supersaturated lime medium, giving rise to expansive ettringite. It is also shown that lowering the concentration of lime in the medium inhibits expansion; this is accomplished by replacing 40% or more of the cement with pozzolan.
Paper ID: CCA10167J