Erratum to “Utilization of aluminum sludge and aluminum slag (dross) for the manufacture of calcium aluminate cement” [Ceram. Int. 35 (2009) 3381–3388] (original) (raw)
Related papers
Ceramics …, 2009
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.
Synthesis of Calcium Aluminates from Non-Saline Aluminum Dross
Materials, 2019
The present work examines the synthesis of tricalcium aluminate (for use as a synthetic slag) from the non-saline dross produced in the manufacture of metallic aluminum in holding furnaces. Three types of input drosses were used with Al2O3 contents ranging from 58 to 82 wt %. Calcium aluminates were formed via the mechanical activation (reactive milling) of different mixtures of dross and calcium carbonate, sintering at 1300 °C. The variables affecting the process, especially the milling time and the Al2O3/CaO molar ratio, were studied. The final products were examined via X-Ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy. The reactive milling time used was 5 h in a ball mill, for a ball/dross mass ratio of 6.5. For a molar relationship of 1:3 (Al2O3/CaO), sintered products with calcium aluminate contents of over 90% were obtained, in which tricalcium aluminate (C3A) was the majority compound (87%), followed by...
Synthesis of Calcium Sulfoaluminate Cements From Al2O3-Rich By-products from Aluminium Manufacture
claisse.info
Calcium sulfoaluminate (CSA) cements are special hydraulic binders, very interesting from both technical and environmental point of view. They contain calcium sulfoaluminate (4CaO•3Al 2 O 3 •SO 3 ), dicalcium silicate (2CaO•SiO 2 ) and calcium sulfates (CaSO 4 •2H 2 O and/or CaSO 4 ) as main components together with tetracalcium-iron aluminate (4CaO•Al 2 O 3 •Fe 2 O 3 ), calcium sulfosilicate (5CaO•2SiO 2 •SO 3 ), calcium-aluminates (3CaO•Al 2 O 3 , CaO•Al 2 O 3 , 12CaO•7Al 2 O 3 ) and -silicoaluminates (2CaO•Al 2 O 3 •SiO 2 , CaO•Al 2 O 3 •2SiO 2 ). Upon hydration, calcium sulfates, belonging or added to CSA clinker, react with 4CaO•3Al 2 O 3 •SO 3 and generate ettringite (6CaO•Al 2 O 3 •3SO 3 •32H 2 O) which, depending on the conditions of its formation, regulates the technical properties of CSA cements (shrinkage compensation or self stressing behaviour or rapid-hardening associated with dimensional stability) [1-11]. 2CaO•SiO 2 can add strength and durability at medium and long ages, while 4CaO•Al 2 O 3 •Fe 2 O 3 and calcium aluminates contribute to ettringite formation; on the other hand, 5CaO•2SiO 2 •SO 3 and calcium-silicoaluminates display a poor hydraulic activity. The distribution of the secondary components is mainly influenced by the synthesis temperature as well as the nature and proportioning of raw materials. Compared to Portland cement production, the manufacturing process of CSA cements has a pronounced environmentally friendly character [4; 12]. In this regard important features are: 1) synthesis temperatures 200°-300°C lower than those required by ordinary Portland cement clinkers; 2) clinkers easier to grind; 3) reduced amount of limestone in the kiln raw mix and, consequently, reduced thermal input and CO 2 generation; 4) greater usability of wastes and by-products. Several industrial residues were successfully experienced as raw materials for the synthesis of CSA cements . The industrial by-products generated by coal-fired power plants can play a very important role ; in particular, pulverized fly ash (PFA, as a source of SiO 2 and Al 2 O 3 ), fluidized bed combustion (FBC) waste (as a source of lime, calcium sulfate, silica and alumina) and flue gas desulfurization (FGD) gypsum (as a source of calcium sulfate) are worthy of consideration because their present utilization degree is still unsatisfactory. PFA generally has a good pozzolanic behaviour and other useful characteristics which can be exploited in a variety of applications, but its unburnt carbon content (generally expressed as loss on ignition, l.o.i.) must be relatively low in order to meet the requirements of the ordinary cement and concrete industry. Ashes originated from either old, poorly efficient plants or modern, environmentally friendly pulverized coal combustors (operating at reduced temperatures) can display unacceptably high l.o.i. values. The utilization of FBC waste, mainly composed by exhausted sulfur sorbent and coal ash, is generally made difficult by its chemical and mineralogical composition. The fairly high amount of lime and calcium sulfate is responsible for exothermal and expansive phenomena during hydration; moreover, the pozzolanic activity of FBC ash is poor, due to its reduced glass content . FGD gypsum can replace natural gypsum in its main application fields (plaster and cement
Use of Industrial Byproducts as Alumina Sources for the Synthesis of Calcium Sulfoaluminate Cements
Environmental Science & Technology, 2011
Calcium sulfoaluminate (CSA) cements are useful hydraulic binders from both a technical and an environmental point of view. The most important properties of CSA cements are regulated by their key component, 4CaO 3 3Al 2 O 3 3 SO 3 (calcium sulfoaluminate). This compound is able to hydrate in three different ways: (a) only with water to give monosulfate and aluminum hydroxide, eq 1; (b) combined with calcium sulfate and water to generate ettringite and aluminum hydroxide, eq 2; and (c) together with lime, calcium sulfate, and water to produce ettringite alone, eq 3
An Experimental Investigation on Use of Secondary Aluminium Dross in Cement Concrete
In the production of Aluminium production, Aluminium dross is a by-product. At present, dross is processed in rotary kilns to recover the Aluminium. Aluminium dross in the form of salt cake is sent to landfills, although it is sealed to prevent from leaching. Leaching of Aluminium dross could harm the environment as it contains fluorides and other salts. Furthermore, much energy is consumed to recover the Aluminium from the dross, this energy can be saved if the dross could be diverted and utilized as an engineering material. The objective of present work is to utilize the Aluminium dross in the natural cycle (closed loop) by using it as an engineered material and to investigate the mechanical properties of new concrete type obtained by adding Aluminium dross, which is an impure Aluminium mixture, obtained from metals melting and mixing with flux. The main advantage of this type of concrete over the conventional ones is the reduction in the quantity of raw materials. 5%, 10%, 15%, 20% and 30 % by weight of cement is being replaced by dross. Then using this concrete, concrete cubes are casted. The casted cubes are tested for compressive strength for 3 days, 7days, 28 days. It is found that 7 days compressive strength has been increased when compared with 3 days compressive strength for 5% replacement. But for rest of the replacements (10%, 15%, 20%& 30%), 7 days compressive strength has been decreased when compared with 3 days compressive strength. Hence, 5% replacement is preferable. The results of this study indicate that Aluminium dross can be used as an ingredient up to 5% to improve expanded concrete/mortar.
Taylor & Francis eBooks, 1990
De-icer salt scaling resistance of CAC concretes exposed to various de-icer salts M. JOLIN, F. GAGNON PART SIX-WASTEWATER APPLICATIONS 23 Field investigations of high performance calcium aluminate mortar for wastewater applications
Behaviour of cement mortars containing an industrial waste from aluminium refining
Cement and Concrete Research, 1999
The physical and chemical interaction between a solid industrial waste from aluminium refining and saturated Ca(OH) 2 solution, as well as the effects of substituting siliceous sand for the waste on the physical and mechanical properties of mortars were studied. The waste is a solid that contains reactive alumina capable of combining with the calcium hydroxide. These reactions result in stable and insoluble compounds. This alumina, together with the halite (also present in the waste composition), chemically react with a saturated solution of Ca(OH) 2 , giving as a main reaction product the so-called Friedel's salt (Ca 4 Al 2 Cl 2 O 6 и 10H 2 O). Strätlingite and Si-hydrogarnets were among other products detected. The waste has a high specific surface area. The cement/waste mixtures therefore require a higher quantity of mixing water than cement/sand mixtures. The result is a decrease of the mechanical strengths and an increase of the total porosity. However, a decrease of the average size of the pores occurs, which can have a positive effect on the durability of the final material.
Preparation of Refractory Calcium Aluminate Cement Composed of 70% Alumina
2004
It has been the aim of this project to produce refractory calcium aluminate cement (CAC) with 70% alumina in the laboratory. Pure calcined alumina and lime were mixed and fired at different temperatures and times in a rotary kiln. When the clinker was formed, it removed out of the furnace and cooled rapidly. The presence of optimized amounts of monocalcium aluminate (CA) and Dicalcium aluminate (CA2) as the major anhydrous phases in clinker were examined by X-ray diffraction method, and the hydraulic properties of powdered samples were measured by evolved heat measurement versus time during setting times. Based on the data acquired by various test methods, 1550 °C and 90 min. were the optimized conditions for preparation of this type of refractory calcium aluminate cement.
Production of Cement Based on Calcium Aluminate by Means of Solid State Reactions
Chemistry & Chemical Technology
Through powder techniques and in situ solid state reactions, a refractory cement CaAl2O4-based was fabricated, using CaCO3 extracted from chicken eggshells and Al as precursor materials. To reduce the particle size and achieve a homogeneous mixture, the powders were subjected to high-energy milling in a planetary mill. The powders resulting from the grinding were compacted to form cylindrical tablets. These samples were pressureless sintered in air. A particle size distribution analysis indicates that they were obtained from the grinding particles ranging in size from nanometers to 2 microns. Differential thermal analysis indicates that the decomposition of CaCO3 begins at 953 K and ends at 1073 K, a situation confirmed by X-ray diffraction analysis, the latter also indicating that the formation of the CaAl2O4 crystalline phase is completed at 1773 K. The microstructure observed by scanning electron microscope shows equiaxial grains in the form of flakes and sizes from 1 to 2 micron...
Investigation into Utilization of Bayer- Al(OH)3 in Production of Calcium Aluminate Cements
Key Engineering Materials, 2004
In this study, samples of Calcium Aluminate (CA) cements produced from reactive alumina and calcite were compared with those samples produced from Bayer -Al(OH)3 and calcite. The raw material mixtures were formed under light pressure into cylinders and sintered at 1350, 1400, 1450 and 1500 0 C. The fired samples were ground to 3300-4400 cm 2 /g Blaine in a laboratory ceramic mill. The physical and mechanical properties of the cement samples were determined. The results of this study suggest that the production of CA -cements containing 71 % Al 2 O 3 was possible using Bayer-Al(OH) 3 and calcite as raw materials.