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  • Separability studies of con...
    Ulsen, Carina; Kahn, Henrique; Hawlitschek, Gustav; Masini, Eldon A.; Angulo, Sérgio C.

    Waste management (Elmsford), March 2013, 2013-Mar, 2013-03-00, 20130301, Letnik: 33, Številka: 3
    Journal Article

    Display omitted ► Reduction of cement paste content on fine recycled aggregates. ► Density and magnetic separation to remove particles with cement paste attached.► Advanced characterization to define liberation of natural aggregates. ► A low-cement paste content recycled sand may be achieved with high mass recovery. ► The change in recycling approach encourages the use of recycled sand. The quality of recycled aggregates from construction and demolition waste (CDW) is strictly related to the content of porous and low strength phases, and specifically to the patches of cement that remain attached to the surface of natural aggregates. This phase increases water absorption and compromises the consistency and strength of concrete made from recycled aggregates. Mineral processing has been applied to CDW recycling to remove the patches of adhered cement paste on coarse recycled aggregates. The recycled fine fraction is usually disregarded due to its high content of porous phases despite representing around 50% of the total waste. This paper focus on laboratory mineral separability studies for removing particles with a high content of cement paste from natural fine aggregate particles (quartz/feldspars). The procedure achieved processing of CDW by tertiary impact crushing to produce sand, followed by sieving and density and magnetic separability studies. The attained results confirmed that both methods were effective in reducing cement paste content and producing significant mass recovery (80% for density concentration and 60% for magnetic separation). The production of recycled sand contributes to the sustainability of the construction environment by reducing both the consumption of raw materials and disposal of CDW, particularly in large Brazilian centers with a low quantity of sand and increasing costs of this material due to long transportation distances.