Abstract
Solidified flowable fill comprising of Type I portland cement, Class F fly ash, fine sand and water, is a porous monolith. In the case of excavatable fill, material mix proportions in the ash must be such that adequate but inexcessive strength is developed. For non-excavatable fill, maximization of fill strength is the primary objective. Furthermore, being that heavy metals are typically present in fly ash, physico-chemical interactions among mix components must mitigate against leaching out of metals. Herein, flowable fill monoliths containing class F fly ash in weight fractions of 0, 5, 10, 15, and 20, were subjected to unconfined compressive strength (UCS) tests and the American Nuclear Society’s ANSI 16.1 leaching test, using de-ionized (DI) water and acidified water (pH = 5.5) as leachants. The results show that comprehensive strength is directly proportional to ash content, reaching 834 kN/m2 for excavatable fill and 3,753 kN/m2 for non-excavatable fill. The diffusion coefficients of arsenic (As) and selenium (Se) from samples decrease sharply with increase in ash content from 5% to 10% and stay relatively low at higher ash content. The leachability indices which are inversely proportional to the quantity of material leached, indicate that the effects of reduction in monolith internal permeability exceed the effects of increasing As and Se content introduced by higher ash content in the monoliths.
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Gaddam, R., Inyang, H.I., Ogunro, V.O., Janardhanam, R., Udoeyo, F.F. (2009). Strength and Leaching Patterns of Heavy Metals from Ash-Amended Flowable Fill Monoliths. In: Yanful, E.K. (eds) Appropriate Technologies for Environmental Protection in the Developing World. Springer, Dordrecht. https://doi.org/10.1007/978-1-4020-9139-1_27
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