Use of bottom ash additions in the production of concrete with recycled aggregates

• Autor(a) principal: Raposeiro Da Silva, Pedro
• Data de Publicação: 2021
• Outros Autores: Silva, Rui V., Brito, Jorge de
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10400.21/14340
• topic: Biomass; Bottom ash; Coal; Concrete; Recycled aggregates; Sewage sludge

This paper provides a literature review on the use of bottom ashes in the production of concrete with recycled aggregates. Three types of bottom ash were studied, namely: biomass bottom ashes, coal bottom ashes and sewage sludge bottom ash. The characterization of these ashes focused on the analysis of their physical, chemical, and mineralogical properties. The effect of these ashes was subsequently studied on the fresh, mechanical, and durability-related performances of concrete. Bottom ashes generally present lower pozzolanicity than that typically observed, for example, in coal fly ashes. Their use as partial cement replacement normally leads to some loss in performance of the resulting cementitious composites. Also, using them as aggregates or in combination with recycled aggregates of other sources similarly causes an overall loss in performance. Nevertheless, such decline is still acceptable and often within manageable limits for the production of concrete under specific conditions including some structural applications. The use of these by-products including recycled aggregates may assist in solving a two-fold problem. Firstly, it reduces the consumption of cement and, consequently, the extraction of natural resources, also including the decrease of the consumption of natural aggregates to produce concrete. Furthermore, it solves the problem of the final destination for the significant quantities of bottom ashes produced by different industrial processes. In general, it is possible to conclude that, in moderate contents and when adequately processed, bottom ashes can be considered as viable substitutes of cement with manageable losses in terms of mechanical and durability-related performances. The use of coal bottom ashes was also found to significantly reduce the drying shrinkage strain of concrete.