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Polishing granite mud, i.e. the residue of the polishing process of granite stone blocks, has been studied for its potential use in heavy clay industry. Due to its properties waste stone mud could be used as a filler (an opening agent) in claybased industry, e.g. in the production of clay bricks, blocks, panels, roofing tiles, or facing bricks. Different mixtures of clay of normal use in brickworks and up to 30 wt.% of mud were prepared on the laboratory scale. The influence of the stone mud addition on the drying and firing process, as well as on the properties of finished products, such as water absorption and compressive strength, was studied. From the laboratory results it can be concluded that a substantial amount (up to 10 wt.%) of granite stone mud may possibly be added into the regular production of heavy clay products. In this way a significant decrease in costs could be achieved due to the partial replacement of basic raw materials and due to the fact that the landfilling of waste stone mud may be avoided.
The processing of new waste-based lightweight aggregates is described. Main components are sludges generated from potable water filtration/cleaning operations and clay-based by-products from washing process of igneous rocks. The complete characterization of residues is reported, including physical and chemical parameters, and their thermal behaviour. Several mixtures were designed, prepared, and fired at different temperatures, trying to use the materials such as they are available. First we attempted to reproduce typical properties of common lightweight aggregates based on natural resources, such as clays. Then, a further approach was followed, involving the production of aggregates with improved mechanical strength. In this attempt, the firing cycle seems to play an important role. The bulk density of this new aggregate is somewhat higher but still low due to the formation of an internal cellular structure made of closed pores and an external shell that is partially vitrified. Microstructural evolution was also evaluated (by SEM) while the expansive behaviour of the most promising formulations was studied by hot stage microscopy.
In waterworks large amounts of sludge have to be discarded. This waste is usually destined to rivers, lakes and landfills, resulting in economic and environmental problems. This work reports on the use of waste (sludge) of a waterworks from South-Eastern Brazil as a raw material in red ceramic. The waste sample was characterized regarding crystalline phases, chemical composition, morphology, cation exchange capacity and particle size. In addition, leaching and solubilization tests were performed. Ceramic pieces containing up to 15 wt.% of waterworks waste powder were prepared by uniaxial pressing and sintered at 950 ºC. The effects of the waste addition on linear shrinkage, water absorption, apparent density, and flexural strength have been determined. The sintered microstructure was evaluated by scanning electron microscopy. The results showed that the municipal waterworks waste could be used for red bricks production, resulting in a new possibility for the recycling of this waste as well as natural resources conservation.
The Egyptian refractory raw materials available for application in the production of acidic and basic refractories are reviewed. Egyptian quartz and quartzite raw materials can be utilized in the production of shaped and unshaped silica refractories for lining coke ovens and ductileiron induction furnaces, respectively. Also, the semi-silica and fireclay bricks currently produced from the available kaolinitic clays can be economically applied for lining steel ladles and tundishes, beside the aluminous fire clay bricks. On the other side, dense and hydration resistant shaped and unshaped lime, dolomite and MgO-dolomite refractories for lining and repairing of steel and cement furnaces can be produced from their available raw materials. In addition, shaped cordierite bodies can be produced as furniture for tunnel kilns used in firing white ware ceramics and forsterite bricks for lining the lower courses of the glass tank heat exchangers from varieties of serpentinite rocks.
The modulus of rupture of four different refractory mixtures for coke ovens repair by hot gunning was determined. The materials were characterized by chemical, granulometric and phase analyses, optical microscopy and apparent density measurements. MOR values were determined by three points flexural test using prismatic specimens obtained by ramming of aqueous mixtures of the monolithic materials and firing. These values were related with the aggregate and bonding phase characteristics of the refractory materials and with the fired bar microstructures. MOR values were also considered to analyze the cohesion of each fired material and correlated with hot adhesion of mixtures on silica bricks. Results show that even though the refractory behavior at working temperatures cannot be directly derived from the modulus of rupture at room temperature (MOR), this value may give some useful indication to make a first selection of hot gunning refractory mixtures.
Capillary ceramic filters were prepared from a quartz-natural zeolite-lead borosilicate glass mixture by uniaxial pressing and sintering at various temperatures. Sintered specimens were characterized by their bending strength, apparent porosity, pore size distribution, and microstructure. The filter sintered at 960 °C shows promising engineering properties for the capillary-system: maximum pore size, bend strength and porosity being 0.6 mm, 30 MPa and 33.45%, respectively.
Weathered granitic rocks from Al-Madina Al-Munawwarah area were experimented for the preparation of cheap technical glassceramic materials. The weathered granitic rocks were about 53.17 wt% of the batch constituents, depending on the composition. The batches were melted and then casted into glass, which was subjected to heat-treatment to induce crystallization. The resulting glass-ceramic materials were mainly composed of diopside, anorthite and wollastonite and mullite, exhibiting fine grains and uniform texture. It has been found that an increasing content of the weathered granitic rocks in the batch constituents, results in increased bulk crystallization.
Mullite-zirconia-silicon carbide composites were synthesized from zircon flour, reactive alumina powder and a-SiC grains with Al powder and CeO2 additives with variable proportions of SiC and reactive alumina. The different physico-mechanical properties of the powder compacts after firing like, firing shrinkage, apparent porosity, bulk density and true density along with the phase composition and microstructure varied with the change in composition and the firing temperature. Al powder influenced the sintering of the composites positively and the proportion of mullite in the fired compacts increased with the increase in firing temperature.
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