Properties of Recycled Concrete Manufacturing with All-in Recycled Aggregates and Processed Biomass Bottom Ash

Abstract

Recycled aggregates (RA) have been extensively studied in the production of concrete. Normally, the coarse fraction of recycled concrete aggregates (RCA) is the most commonly used to manufacture recycled concretes. The manufacturing of concrete with fine fraction of RCA and/or recycled mixed aggregates (RMA) (from a mix of concrete, asphalt, masonry, etc.) has not been studied in depth. In most cases, the recycling plants produce RA with an ALL-IN particle size distribution. These recycled materials could be named as ALL-IN RECYCLED CONCRETE AGGREGATES (aiRCA) and ALL-IN RECYCLED MIXED AGGREGATES (aiRMA). Applying these aiRCA or aiRMA, limiting the percentage of the substitution of natural aggregates (NA) by the aiRCA, is more beneficial for both the production costs and the environment. In recent studies, other by-products, such as biomass bottom ash (BBA) were used in concretes, substituting natural sand (NS) and improving the mechanical properties in concretes with low quantities of cement. It is possible to improve the properties of the BBA via mechanical processes (like screening or flotation) to reduce the organic matter content and there by obtain processed BBA (Pr-BBA). This study provides interesting data on the mechanical and durability properties of the concretes manufactured with 30% aiRCA and aiRMA, and also by applying different replacement rates (0, 15, and 30%) of NA by BBA and Pr-BBA. The mechanical and durability properties were analysed over different time durations in different mixtures. It was demonstrated that it is possible to apply these recycled materials in non-structural concrete mixtures by limiting the replacement rate. The application of BBA and Pr-BBA reduced the properties of the concrete. However, this reduction was less significant with the use of Pr-BBA.