Experimental Investigation and Modeling of Sulfoaluminate Cement Preparation Using Desulfurization Gypsum and Red Mud

Abstract

Desulfurization gypsum, the byproduct from wet flue gas desulfurization, and red mud, from the production of aluminum oxide, are two bulk industrial solid wastes that trigger many local environmental problems in China. This study aims to jointly utilize them. Through experimentation and modeling using FactSage, it has been found to be feasible to prepare sulfoaluminate cement using these wastes. The calcination temperature in the preparation was as low as 1250–1300 °C, and the main mineral phases of the cement clinker were 3CaO·3Al2O3, CaSO4, β-2CaO·SiO2, and 2CaO·Fe2O3. The cement clinkers tested showed excellent mechanical strength performances. This process was found to be an efficient way to consume industrial solid wastes, with the total proportion of desulfurization gypsum and red mud over 70–90% by mass in the raw materials. The sulfoaluminate cement products have outstanding cost superiority over Portland cement because of their low material costs, low material pretreatment costs, and low calcination temperature. Moreover, this technology could bring about immense environmental and social benefits in terms of waste consumption, energy conservation, and CO2 reductions. This technology has considerable prospects, and it is worth undertaking further research into its potential applications.

Use of fly ash and phosphogypsum for the synthesis of belite-sulfoaluminate clinker

“…This is also the case for belite, which is usually present in calcium sulfoaluminate cements, as its hydration is also typically slow but provides long-term strength (1). Furthermore, the poor hydraulic ability of gehlenite means that it contributes little to the compressive strength of a cement (11). The slight decrease in compressive strength of the cement pastes based on clinker mixtures B and C heated at 1220°C is thus most probably the result of the higher quantity of phases that do not influence cement strength, such as gehlenite and ternesite.…”

“…Studies investigating the production of BSA cements from waste materials or by-products are increasingly commonplace (9)(10)(11)(12)(13)(14). Gallardo et al (15) reported the fabrication of sulfoaluminate belite clinker containing Ca 4 Al 6 O 12 SO 4 as its main phase from the mixture of aluminium dross, fluorogypsum, fly ash and CaCO 3, with heat treatment applied in the temperature range from 1100 to 1400°C.…”

“…Industrial wastes and by-products are used not only in blended cements or as mineral additives in concrete, but may also be added during clinkerisation itself, partially or totally replacing the virgin raw materials. One solution for recycling NORMs such as fly ash and phosphogypsum is the synthesis of belite-sulfoaluminate cement clinkers (7,11,13,14). Commonly, the concentration of radionuclides originating from such residues is decreased in the resulting products due to the dilution effect (26,27).…”

Effect of Residual CaSO4 in Clinker on Properties of High Belite Sulfoaluminate Cement Based on Solid Wastes

“…The raw materials for production are usually limestone, clay, bauxite, and gypsum [1,2]. However, with the long-term and large-scale exploitation of natural resources, the above-mentioned raw materials are becoming more and more scarce, and all kinds of industrial solid wastes are beginning to be used as alternative raw materials, including calcium solid waste materials such as marble sludge waste [3], steel slag [4,5], lithium slag [6] and municipal solid incineration wastes [7], sulfur solid waste materials such as phosphogypsum [8,9] and desulfurization gypsum [10,11], and aluminum-silicon solid waste materials such as fly ash (FA) [11][12][13][14][15][16], coal gangue [17], red mud [10,18], aluminum anodizing sludge [19], and tailings [20]. C 4 A 3 S is an indispensable component in the hydration of HBSAC, and the main chemical reactions in the hydration process are shown in Equations (1) and (2).…”

Research on the Preparation and Properties of High Belite Sulphoaluminate Cement (HBSAC) Based on Various Industrial Solid Wastes

“…Li et al [17] employed lithium mica slag, whose main components are C and Ca(AlO 2 ) 2 , and low grad bauxite to prepare HBSAC with limestone and bauxite at 1270–1320 °C. Wang et al [18] substituted natural gypsum for desulfurized gypsum, bauxite for red mud partially or fully to prepare HBSAC with limestone and bauxite at 1300 °C, the desulfurization gypsum and red mud can make up 70%–90% by mass of the total raw materials; and red mud as a resource of iron and aluminium in the preparation of HBSAC can also be seen in reference [19]. Tangshan Polar Bear Building Materials Co., Ltd. [20] adopted fly ash and desulfurization gypsum to produce fast-setting and quick-hardening HBSAC with other natural resources, which is popular in the Chinese cement market and has been applied in the Qingdao Airport and oilfields in Dongying, achieving good economic benefits.…”