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Reuse of woody biomass fly ash in cement-based materials: leaching tests

pubblicazioni - Presentazione

Reuse of woody biomass fly ash in cement-based materials: leaching tests

Nel presente studio è stata presa in considerazione una bio-cenere proveniente dalla combustione di cippato di legna. In una prima fase tale cenere è stata caratterizzata dal punto di vista delle proprietà fisiche, della composizione chimica e mineralogica e delle proprietà di lisciviazione di metalli pesanti.

Woody biomass fuels represent one of the most interesting categories of renewable energy resources. Woody biomass fly ash (bio-ash) is the fraction of residual ash that is trapped in filters/or precipitators of the combustion plants of such fuels. The content of heavy metals in the bio-ash may be a very important factor in preventing or limiting its valorisation. Decontamination techniques of such a waste could be requested prior to its reuse in agricultural and industrial applications. In the present study, a bio-ash coming from the combustion of virgin wood chips was first characterised for its physical properties, chemical and mineralogical composition, and heavy metal leachability. Two different leaching tests, the Italian leaching test using deionised water as leachant and the USA-EPA TCLP leaching test using acetic acid solution, were used in order to evaluate the leaching behaviour of the bio-ash under different environmental scenarios. In a subsequent phase of the experimentation, the feasibility of using woody biomass fly ash as a mineral admixture in cement-based materials was investigated. In particular, a blended cement with 70 wt. % Portland cement and 30 wt. % bio-ash was formulated and used for the preparation of cement pastes with a water/binder weight ratio of 0.50. Cubic specimens were made and, after 28 days of curing at 20 °C and 100% RH, these specimens were tested for heavy metal leachability through the use of a sequential leaching protocol, at a constant pH of leachant (deionised water; pH=4.0)..

 

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