Some Aspects of Durability of High-Volume ASTM Class F (low-calcium) Fly Ash Concrete

Low-calcium fly ash, ASTM Class F, is being increasingly incorporated into portaldn cement concrete as a partial replacement for cement. The replacements commonly used are 15 to 25 percent by weight of cement. This paper presents data on several aspects of durability of this new type of concrete. The aspects discussed include freezing and thawing cycling, resistance to chloride ion diffusion, deicing salt scaling resistance, carbonation, and volume stability. Data on the role of high volumes of fly ash to control alkali-silica reaction in concrete are also presented. It is concluded that, in general, high-volume fly ash concrete has excellent durability characteristics. The only exception is the deicing salt scaling tests, in which the above concrete performs poorly.