Use of cement dust in the manufacture of vitrified sewer pipes S.A. El Sherbiny a , N.F. Youssef b, * , O.A. Ibrahim a , M.F. Abadir a a The Chemical Engineering Department, Faculty of Engineering, Cairo University, Giza, Cairo, Egypt b Housing and Building Research Centre, 87 Tahreer Street, P.O.B 1770, Dokki, Cairo, Egypt Accepted 23 January 2004 Abstract Waste by-pass cement dust was added in different percentages ranging from 2% to 10% to a standard mix for sewer pipes manufacture, as a substitute for expensive feldspar. It was found that a mix consisting of 45% kaolin, 36% ball clay, 9% grog and 10% by-pass dust and fired at a temperature of 1300 °C for 4 h yielded samples that meet the standards. It was possible to reach a water absorption of 4%, a modulus of rupture of 7.8 MPa and a resistance to acids and alkalis conforming with standard values. A test pipe was fabricated by vacuum extrusion using the suggested composition and was found to withstand a hydraulic pressure of 14 MPa for one minute without the appearance of any cracks. Ó 2004 Elsevier Ltd. All rights reserved. 1. Introduction and objectives Vitrified clay pipes used for sanitary drainage are un- ique in their corrosion and abrasion resistance, for they do not rust, shrink, elongate, bend, erode, oxidize or deteriorate (Eng. Manual Nat. clay pipe Inst, 1998). Besides, their life expectancy exceeds 100 years and the raw materials used in their production are cheap and available (Shawa, 1965). These pipes are usually manu- factured by mixing together different types of clays, to- gether with a non-plastic addition such as flint or grog and a fluxing agent, commonly feldspar (Kepco, 1987). The raw mix is first water agitated, extruded in a pug mill, then dried and fired at temperatures usually exceeding 1200 °C. A variety of clay types can be used ; it is common to use a blend of plastic clay (of the ball clay type) to- gether with a less plastic component of the kaolin type. In Egypt, Aswan ball clay is usually blended with any other type of local kaolin. Recently, El Kholi et al. (1994) have used a South Sinai kaolin (from Khaboba region) which, because of its high alkali content gave a suitable vitrified body by firing at 1220–1250 °C, with- out the use of any fluxing agent. Table 1 shows the requisites that have to be fulfilled by vitrified pipes ac- cording to ES 65 (1986) These standards are also com- patible with BS/EN 295-91 (1991) and ASTM C-700–83 (1983). On the other hand, cement dust is a hazardous solid waste that is produced by the cement industry. It is produced in two forms: either as kiln dust, which leaves the kiln with the flue gases or as by-pass dust which is associated with part of the flue gases that are made to leave the kiln near its upper end in order to eliminate as much as possible alkali salts (essentially NaCl and KCl) which can negatively affect the properties of the pro- duced cement. Duschene and Readon (1998), in their attempt to study the leaching behaviour of this dust, have stated that it consists of extremely fine particles (few microns in particle size) constituted mainly by calcium, sodium and potassium salts. The possibility of using cement dust as an alkaline waste together with other spent wastes has been studied by Glasser (1999) who concluded that the leachate of this dust could be incorporated with inert wastes such as fly ash to form potential cementitious materials. In the clay industry, on the other hand, cement dust was incorporated, as a fluxing agent, with clay bricks (Elwan et al., 1999) and recently, as a partial re- placement of feldspar in the manufacture of wall tiles Waste Management 24 (2004) 597–602 www.elsevier.com/locate/wasman * Corresponding author. Tel.: +202-7493046; fax: +202-3351564. E-mail addresses: dr_n_youssef@hotmail.com, n.youssef@hbrc. edu.eg (N.F. Youssef). 0956-053X/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.wasman.2004.01.007