Internal sulfate attack on precast concrete products has been investigated by the author. The cause for these failures has been identified as delayed ettringite attack, a process whereby the normal formation of ettringite in plastic portland cement concrete is either delayed or is formed and then decomposed, only to destructively reform in the hardened concrete after months or years of exposure to water. Reasons for the apparent newness of the phenomenon, and methods for preventing it, are given on the basis of investigations of incidences during the past several years.
