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


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

Author(s): V. M. Malhotra, G. G. Carette, A. Bilodeau, and V. Sicasundaram

Publication: Special Publication

Volume: 126


Appears on pages(s): 65-83

Keywords: alkali-aggregate reactions; chloride-ion contamination; concrete; deicing; fly ash; freeze-thaw durability; scaling; volume change; Materials Research

Date: 8/1/1991

Low-calcium fly ash (ASTM Class F) is being increasingly incorporated into portland cement concrete as a partial replacement for cement. The replacements commonly used are 15 to 25 percent by weight of cement. CANMET has recently developed concrete in which high volumes of low-calcium fly ash are incorporated with slumps in excess of 150 mm being obtained by the use of large dosages of superplasticizers. Typically, in high-volume fly ash concrete, cement content is kept at about 150 kg/m3 and the water-to-cementitious materiaes ratio is about 0.32. The fly ash content is about 56 per cent by weight of the total cementitious material. 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.