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Approximately 22 kg of spent pot lining is generated (SPL) per ton of aluminum produced by electrolytic cells. Untreated SPL is classified as hazardous industrial waste due to its hydroreactive nature and the presence of leachable cyanide and fluoride compounds. After treatment with the Low Caustic Leaching and Liming (LCL&L) industrial process, the refractory portion of the SPL is transformed into an inert material called LCLL. This project analyzed the use of LCLL as a cement binder. The reactivity of LCLL was studied using the compressive strength activity index, and RILEM R³ tests. The results showed that LCLL is composed of stable crystalline phases such as corundum, albite, and nepheline, and contains graphite. The improvement of LCLL reactivity was explored by calcination and the addition of synthetic fluorite, also from the LCL&L process. The results showed a significant improvement in reactivity with the formation of a larger amount of reactive amorphous phases with high silica and alumina content with optimum fluorite content of 10%. Calcined LCLL showed similar reactivity to fly ash, without retarding effect, with compressive strength equivalent to cement at 112 days and the formation of a new phase rich in carboaluminate.

Spent pot lining (SPL) is an industrial waste generated from aluminum electrolysis cells. LCLL-ash is the inert by-product coming from the treatment of the SPL refractory fraction at the SPL treatment plant (Jonquière, Canada). LCLL-ash has been ground to the fineness of the cement to substitute a part of cement in cement pastes. However, LCLL-ash contains higher contents of silica and alumina compared to Portland cement, which can affect the composition, the morphology and the mechanical properties of the binder hydrates (e.g. the Calcium-[Aluminum]- Silicate Hydrates, C-[A]-S-H) with an important effect on the durability. This paper focuses on the investigation of the microstructure and the mechanical properties of LCLL blended cement pastes by applying multiple techniques including scanning electron microscopy, X-ray diffraction, and microindentation at the level of the cement paste. The water-to-binder ratio (w/b) is fixed at 0.35. The effect of the different proportions of LCLL-ash on the microstructural and mechanical properties of blended cement pastes is presented and discussed with relation to the normal Portland cement paste.

Today, in Russia, carbide - silicon and aluminate - silicate packing masses are generally used for lining blast - furnace chutes. They contain re-fractory clay, coal-tar pitch and resins as binders which emit carcinogenic sub-stance dangerous for a human organism. Thirty compositions of chute concrete masses excluding any carcinogenic substance were studied and tested on a chute by the Siberian State University of Industry in conjunction with the Kuznetsk Metallurgical Combine company. The best results were obtained with the following composition: 75 % fused electrocorundum, 20 % refractory clay, 5 % high-alumina cement and 7.3 % water (above 100 %). Thermal resistance in heat changes was above 25 cycles at 800 ‘C, apparent density was 2.54 to 2.75 g/cm3, compressive strength was 76.6 and 79.2 MPa at 110 ‘C and 1450 ‘C, respectively, slag resistance was 0.1 to 0.2 mm at 1450 ‘C, firing shrinkage was 0.2 % with no corrosion observed. The composition developed increased the service life by 10 times compared with the composition generally applied and does not emit any carcinogenic matters. However, in view of the economic crisis and high cost of the electrocorundum, its application is limited. Therefore, we have developed compositions with a high - alumina product (HAP), the waste from the Yurga abrasive works, as a replacement for the electrocorundum. They are as follows: (i) 35 % HAP, 20 % fireclay powder, 15% refractory clay, 30 % waste from the production of silicon carbide; (ii) 48 % HAP, 20 % fireclay powder, 15 % refractory clay, 32 % waste of silicon car-bide with a particle size distribution of 3 to 0 mm. These compositions exhibit < 50 % reduction in strengths (from 80 to 40 MPa) at 1450 ‘C with other indices (slag resistance, iron resistance, apparent density and shrinkage) being the same as for compositions containing pure fused electrocorundum. Their cost is simi-lar to that of the concrete masses generally used but the service life is 4 times longer which was proved by testing in a central chute of a blast furnace.

Recent attempts at restoring the structural use of high-alumina cement are discussed within the framework of the history of the use of this type of cement and the subsequent failures. The author describes his experience in testing this material. The article then reports on recent problems with high-alumina cement use and its durability. While high-alumina cement is a valuable material for use in refractory concrete and other special purposes, its use for structural concrete is a risk that is avoidable.

Studies of slag activation by alkalies have been carried out since 1973 at the Institute of Building and Refractory Materials, Academy of Mining and Metallurgy, in Cracow, Poland. Laboratory tests were followed by production of the activated slag on a large scale. It appeared that the new cementing material composed of the granulated blast furnace slag mixed with an alkaline activator showed high strength and corrosion resistance. The present work deals with the problem of reinforcing steel corrosion in the alkali-activated slag mortar exposed to the attack of concentrated chloride solution. The observations of reinforcement in ordinary portland cement (OPC) mortars, OPC plus silica fume (SF) mortar, or OPC plus limestone flour mortar were carried out simultaneously. The resistance of alkali-activated slag mortar to the attack of a solution of high Cl- concentration was proved previously. The effective, protective action of the alkali-activated slag mortar was confirmed by electrochemical measurements and weight loss determination after 365 days' exposure to a chloride solution. A similar effect was found in the case of silica fume or limestone flour addition to the OPC mortar, but the corrosion of the reinforcement was clearly visible, as shown by corrosion pits in the reference standard OPC mortar samples.