Utilization of ferrosilicium plant gas scrubbing dust (FPGD) in hydroengineering concrete: A case study

Abstract

At the concrete plant of the Krapivin Hydroengineering System, a plant has been built for introduction of FPGD into the concrete mix (Fig. i). The plant is operating effectively. FPGD is transported in special containers (i) of 6.5 m 3 (1.3 tons) each. A drop-side KAMAZ truck with a trailer carries six containers with a total pay cargo of 8 tons, covering a distance of 235 km from the Kuznetsk Ferroalloy Factory, which is equipped with an installation for dry removal of gas scrubbing products.The containers are unloaded by a telpher into i00 m ~ vessels 2 by hydraulic washing to prevent dusting.The vessel is furnished with heating system 3 and bubbler mixer 4. After loading the suspension, brought to a calculated concentration level, flows by gravity through a pipe with a steam satellite into water dispenser 5. It is then sent into mixer 6.The mortar water dosed for the mixer is fed as a suspension with a certain quantity of FPGD.The amount of this water depends on the amount of water in the fillers, which is subtracted from the specification-required water content when the mix is adjusted for moisture level.The lower the moisture level of the fillers, the larger the quantity of mixing water and, therefore, the greater the amount of FPGD additive.The optimal density of the suspension is 1080 kg/m 3, which corresponds to a 20% concentration, or 200 kg of FPGD per I000 kg of suspension.At a high moisture content of the fillers, the amount of FPGD that can be added to the concrete with this process is limited.In the Krapivin Hydroengineering System, where the moisture content of the fine filler is quite high, a preliminary study was conducted to determine the general efficiencv of introducing a small amount of FPGD.The results are presented in Tables 1 and 2. The efficiency factor K was calculated from Ceq = C I-~A'~ C I, (I)where Ceq is the content of cement in a composition of equivalent strength without FPGD; C I is the lowered content of cement in the composition of the same strength with FPGD; K is the equivalence (efficiency) coefficient when cement is substituted by FPGD; ~ is the content as a fraction of Cz. Equation (i) holds for conditions of equal water demand of the mixes.Ceq can be calculated from actual strength for a given cement grade.The values of C I are given in Table i.The experiments indicate that, by adding a small amount of FPGD, large cement savings can be achieved.With increasing amount of FPGD added, the air content becomes lower but not to an extent where it would affect molding convenience and durability.