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Abstract: In this research, the usability of aluminium dross - an industrial by-product - as an additive for the brick industry was investigated. Brick clay was used to prepare the mixtures, to which different amounts (6-24 wt%) of dross were added. The optimal moisture content (20 wt%) required for forming was determined in preliminary experiments. Volume and weight changes during drying and firing were calculated. Compressive strength, bulk density and water absorption tests were performed on the fired samples. As the most often used additives of the brick industry (e.g. sawdust and petroleum coke) may interact with a possible new additive during firing, mixtures containing 3.35 wt% sawdust and 1 wt% petroleum coke were also prepared. Our results showed that increasing the amount of dross reduced drying and firing shrinkage as well as body density, but increased water absorption. Compressive strength varied inversely to the dross content.
Keywords: additive, aluminium dross, ceramics, fired clay bricks, industrial by-product, recycling
Introduction
In the production of industrial products, almost always a by-product is created, the storage and disposal of which causes many problems for companies. Industrial waste accumulates over time and causes serious environmental and health damage in the long run [1, 2]. Aluminium industry is one of the industries producing the largest amount of hazardous waste - more than 4.5 billion kilograms of aluminium waste per year worldwide [3, 4, 5]. For this reason, it is important to recycle these industrial wastes and to create products that are useful to society and harmless to the environment.
One of the by-products of aluminium production is the slag, which is formed by the oxidation of molten aluminium due to the metal-air contact. The alumina generates a long, continuous layer on the surface of the melt, thus a certain amount of metallic aluminium is also present in this layer. Salt treatment is used to minimize oxidation [6, 7]. Typically, two different types of slag are distinguished: primary or white slag and secondary or black slag. 15-20% and 10% of aluminum can be recovered from white and black slag, respectively. Various methods, such as pyrometallurgy or hydrometallurgy, are developed to use slags as a secondary raw material but the amount of the recovered, usable material is small [8, 9].
The...