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Abstract

The influence of fly ash (FA) fineness and a high cement replacement ratio on concrete properties was investigated. Class F FA with an original fineness of 3,150 cm2 /g (3F) and a high fineness of 5,690 cm2 /g (5F) was used; high cement replacement ratios of 30%, 40%, 50%, and 60% by FA with different levels of fineness (two groups: 3F30, 3F40, 3F50, 3F60, and 5F30, 5F40, 5F50, 5F60 by weight of cement) were selected to produce the blended cement concrete. Tests regarding the heat of hydration, compressive strength, water absorption, rapid chloride penetration, and Mercury intrusion porosimetry were performed. The FA with fineness of 5,690 cm2 /g improved concrete properties more effectively than did the FA with fineness of 3,150 cm2 /g. The compressive strengths of concretes with FA of 40% or less (3F30, 5F30, 5F40) were higher than that of ordinary Portland cement at 91 days. This indicates that the cement replacement ratio by FA should not exceed 40%. The incorporation of FA reduced the maximum heat of hydration, total charge passed, and capillary pores of concrete. Based on the results, FA concrete with fineness of 5,690 cm2 /g and a cement replacement ratio of 40% had the most influential properties.

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