Utilization of aluminum sludge and aluminum slag (dross) for the manufacture of calcium aluminate cement E.M.M. Ewais a, * , N.M. Khalil b , M.S. Amin c , Y.M.Z. Ahmed a , M.A. Barakat d a Refarctory & Ceramic materials Lab (RCML), Central Metallurgical Research and development Institute (CMRDI), P. O. Box 87 Helwan, 11421 Cairo, Egypt b Chemistry Department, Faculty of Science, Sebha University, Libya c Chemistry Department, Faculty of Science, Ain Shams University, Cairo, Egypt d Chemical & Electrochemical Metallurgy Laboratory, Research and development Institute (CMRDI), P.O.Box 87 Helwan 11421Cairo, Egypt Received 19 March 2009; received in revised form 28 April 2009; accepted 6 June 2009 Available online 7 July 2009 Abstract Four calcium aluminate cement mixes were manufactured from aluminum sludge as a source of calcium oxide and Al 2 O 3 and aluminum slag (dross) as a source of aluminum oxide with some additions of pure alumina. The mixes were composed of 35–50% aluminum sludge, 37.50– 48.75% aluminum slag (dross) and 12.50–16.25% aluminum oxide. The mixed were processed then sintered at different firing temperatures up to 1500 8C or 1550 8C. The mineralogical compositions of the fired mixes investigated using X-ray diffraction indicated that the fired mixes composed of variable contents of calcium aluminate (CA), calciumdialuminate (CA 2 ), calciumhexaaluminate (CA 6 ) in addition to some content of magnesium aluminate spinel (MA). Sintering parameters (bulk density, apparent porosity and linear change) and mechanical properties (cold crushing strength) of the fired briquettes were tested at different firing temperature. Refractoriness of the cement samples manufactured at the optimum firing temperature was detected. Cementing properties (water of consistency, setting time and compressive strength as a function of curing time up to 28 days of hydration) of pasted prepared from the manufactured cement mixes at the selected optimum firing temperatures (1400 8C or 1500 8C) were also tested. Cement mixes manufactured from 45 to 50% aluminum sludge, 37.50–41.25% aluminum slag (dross) with 12.50–13.75% alumina were selected as the optimum mixes for manufacturing calcium aluminate cement since they satisfy the requirements of the international standard specifications regarding cementing and refractory properties as a result of their content of CA (the main hydraulic phase in calcium aluminate cement) and CA 2 (the less hydraulic but more refractory phase). Although the recognized high refractoriness of CA 6 , its formation affect badly the cementing properties of the other non-optimum mixes. # 2009 Elsevier Ltd and Techna Group S.r.l. All rights reserved. Keywords: Aluminum sludge; Aluminum dross; Calcium aluminates; Refractory cement 1. Introduction Since its discovery at 1908 by the French scientist Paid several research works were interested with calcium aluminate cement ‘‘refractory cement’’. Calcium aluminate cement is one of special cement characterized among others with developing about 80% of its ultimate strength after only 24 h of beginning of the hydration [1]. This feature enables its use as a very rapid hardening structural material in the busy locations such as factories and military places [2]. Other applications of calcium aluminate cement include industrial flooring products (such as cast house floors), chemical resistant mortars and concretes, sewer applications, expansive grouts, floor screeds, tile adhesives, protective coatings and in building chemistry products (whereas ordinary Portland cement is combined with it to give desired setting times) [3,4]. In addition, pure calcium aluminate technology has been used to rehabilitate dam spillways and structures affected by biogenic corrosion, such as manholes and pipes [4]. However the most important feature of calcium aluminate cement is its capability to withstand high firing temperatures up to 2000 8C depending on the type of the cement and its content of impurities [5]. In the field of high temperature applications, the type of cement used is determined by the required refractoriness [1]. Calcium aluminate cement is becoming the binder of choice for refractory formulators as the properties of monolithic refractories approach, and in some www.elsevier.com/locate/ceramint Available online at www.sciencedirect.com Ceramics International 35 (2009) 3381–3388 * Corresponding author. Tel.: +20 2 38621782; fax: +20 2 38621782. E-mail address: dr_ewais@hotmail.com (E.M.M. Ewais). 0272-8842/$36.00 # 2009 Elsevier Ltd and Techna Group S.r.l. All rights reserved. doi:10.1016/j.ceramint.2009.06.008