Investigation Into the Long-Term in-Situ Performance of High Fly Ash Content Concrete Used for Structural Applications

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Title: Investigation Into the Long-Term in-Situ Performance of High Fly Ash Content Concrete Used for Structural Applications

Author(s): M. R. H. Dunstan, M. D. A. Thomas, J. B. Cripwell, and D. J. Harrison

Publication: Special Publication

Volume: 132

Issue:

Appears on pages(s): 1-20

Keywords: alkali-aggregate reactions; carbonation; compressive strength; chlorides; concrete durability; concretes; density (mass/volume); fly ash; marine atmospheres; mix proportioning; permeability; strength; sulfates; water-cementitious ratio; Materials Researc

Date: 5/1/1992

Abstract:
Presents results of investigations carried out on high fly ash content concrete (HFCC) cores removed from several structures constructed in the U.K. since 1979. Structures investigated included a road pavement, a major road viaduct, water-retaining and industrial structures, and a slipway subjected to marine exposure. Concrete properties measured after 10 years of service include compressive strength, depth of carbonation, permeability, and chloride and sulfate penetration profiles. In addition, petrographic analysis of thin sections was also undertaken. The HFCCs studied were designed considering the fly ash to be just a further ingredient in the concrete rather than as a cement replacement. This led to higher fly ash contents and lower cement contents than is generally normal practice. The structures examined were in excellent condition after 10 years. Results show a durable concrete exhibiting increases in compressive strength beyond 28 days, little evidence of carbonation, low to average permeability, and resistance to chloride penetration. In this respect, it is significant that at the marine exposure sites, the chloride concentrations decreased significantly with depth. No evidence of alkali-silica reaction was detected in spite of reactive aggregates being present in some of the concretes.