SCC with Ground Bottom Ash from Municipal Solid Wastes Incinerators

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Title: SCC with Ground Bottom Ash from Municipal Solid Wastes Incinerators

Author(s): Silvia Collepardi, Mario Collepardi, Giacomo Iannis, and Alessandro Quadrio Curzio

Publication: Special Publication

Volume: 289

Issue:

Appears on pages(s): 1-12

Keywords: Durability. Fly ash. Ground bottom ash. Municipal Solid Wastes Incinerators. Self-compacting concrete. Shrinkage-reducing admixture. Silica fume. Superplasticizer.

Date: 9/14/2012

Abstract:
Ground bottom ash (GBA) from Municipal Solid Wastes Incinerators (MSWI) does not perform as well as other mineral additions -such as silica fume or fly ash produced by coal burning- due to the presence of aluminium metal particles which react with the lime formed by the hydration of portland cement and produce significant volume of hydrogen in form of gas bubbles which increase the porosity of concrete and reduce its strength. Due to this drawback, a new process was developed to separate the aluminium metal particles through a mechanical removal of metals and a wet grinding of bottom ashes. At the end of the process, GBA was used as aqueous slurry to replace portland cement. In the present work GBA with a maximum size of 1.7 mm (0.07 min) was used to replace about 10% of portland cement in self-compacting concretes (SCC). Mixtures with shrinkage-reducing admixture (SRA) and a CaO-based expansive agent were also manufactured to reduce the drying shrinkage and the related cracks. Moreover, an alternative way to reduce both number and length of cracks was adopted by using SRA combined with polyvinyl alcohol (PVA) macrosynthetic fibres. Corresponding mixtures with silica fume or fly ash were also manufactured. GBA performed as well as silica fume in terms of mechanical properties, durability and crack behavior, and much better than fly ash.