United States Department of Transportation
i
Beneficial Reuse of Landfilled Fly Ash in Transportation Infrastructure
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2024-05-01
[PDF-4.30 MB]
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Edition:Final Report
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Abstract:This research explores the influence of thermo-mechanical beneficiation methods on the physicochemical characteristics and reactivity of fly ashes disposed of in landfills (LFAs) obtained from power plants in Wyoming and Colorado, USA. An in-depth assessment was conducted on the mechanical and performance aspects of mortar samples incorporating these LFAs, including reactivity, compressive strength, electrical resistivity, resistance to alkali-silica reaction-induced expansion, water absorption, and chloride permeation. The findings indicate that the beneficiation processes effectively enhanced the properties of the substandard ashes, ensuring that all beneficiated ashes met the rigorous standards set by ASTM C618. Thermo-mechanical beneficiation notably improved the physicochemical properties of LFAs, resulting in a reduction in loss on ignition (LOI) and an increase in fineness. The results demonstrated enhancements in the strength activity index of all LFAs post-beneficiation, surpassing the minimum requirement of 75% at 28 days. Furthermore, beneficiation increased heat release and calcium hydroxide consumption, indicating improved pozzolanic reactivity. In most instances, the mortar samples exhibited comparable or superior mechanical and durability performance compared with ASTM C618-compliant fly ash. These findings underscore the potential of beneficiated and reclaimed LFAs as practical alternatives in concrete production, particularly in light of the expected shortage of fly ash in the U.S. and globally.
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