Strength brick

Brick linings, like other masonry structures, have low flexural and tensile strength but high compressive strength. Brick linings, especially on vertical walls, must, therefore, be designed so that the bricks and mortar are always under a compressive load-... 

The feeding cavity (hole) is the most abraded part of the furnace. The material of the feeding hole should withstand thermal shocks, mechanical shocks, and abrasion. If material of the feeding hole is worn out, it is a path for the heat flow and instability in the service of the furnace. The lower part of the feeding hole is made from high-strength bricks or castables, while the upper part is made from the castables with sufficient thermal shock resistance (above 30 thermal air cycles). Sometimes metallic fiber is added to castables to increase the abrasion and thermal shock resistance. 

Another measure of refractoriaess is the hot-compressive strength or hot-load test for refractory bricks or formed specialties. The specimen carries a static load from 69 kPa (10 psi) to 172 kPa (25 psi). It is heated at a specific rate to a specific temperature which is then held for 1.5 h, or it is heated at a specific rate until it fads. The percent deformation or the temperature of fadure is measured. The procedure is described ia ASTM C16. 

High Alumina Refractories. The desired alumina content, from 100% to just above 45%, is obtained by adding bauxites, synthetic aluminosihcates, and synthetic aluminas to clay and other bonding agents. These refractories are used in kilns, ladles, and furnaces that operate at temperatures or under conditions for which fireclay refractories are not suited. Phosphate-bonded alumina bricks have exceptionally high strength at low to intermediate temperatures and are employed in aluminum furnaces. High alumina and mullite are used in furnace roofs and petrochemical apphcations. 

After drying, the bricks ate put into a kiln where the temperature is raised slowly to between 870 and 1316°C or higher depending on the temperature needed to fuse the clay. With the clay particles pattiaHy melted and fused together, the brick is a ceramic material with exceHent strength and fire resistance. 

The fundamental goal in the production and appHcation of composite materials is to achieve a performance from the composite that is not available from the separate constituents or from other materials. The concept of improved performance is broad and includes increased strength or reinforcement of one material by the addition of another material. This is the well-known purpose in the alloying of metals and in the incorporation of chopped straw into clay for bricks by the ancient Egyptians and plant fibers into pottery by the Incas and Mayans. These ancient productions of composite materials consisted of reinforcing britde materials with fibrous substances. In both cases the mechanics of the reinforcement was such as to reduce and control the production of cracks in the brittle material during fabrication or drying (2). 

Type of brick Typical composition Approx. bulk density, Ib/fF Fusion point, F. Cbemical nature Deformation under hot loading Apparent porosity, % Perme- abibty Hot strength Thermal shock resistance Cbemical resistance ... 

Compared with brick, castables are less dense, but this does not really mean that they are less serviceable, as their cements can hydrate and form gels which can fill the voids in castables. Extra-large voids do indicate less strength regardless of filled voids and dictate a lower allowable gas velocity. If of the same density as a given brick, a castable wiU result in less permeation. 

The word "composites" has a modern ring. But using the high strength of fibres to stiffen and strengthen a cheap matrix material is probably older than the wheel. The Processional Way in ancient Babylon, one of the lesser wonders of the ancient world, was made of bitumen reinforced with plaited straw. Straw and horse hair have been used to reinforce mud bricks (improving their fracture toughness) for at least 5000 years. Paper is a composite so is concrete both were known to the Romans. And almost all natural materials which must bear load - wood, bone, muscle - are composites. 

Kelly, B.T., The effect of radiolytic oxidation on the graphite moderator brick strength in advanced gas-cooled reactors, Nucl. Energy, 1984, 24(3), 265 272. 

Both our new chemistry building and the science of thermodynamics are functional, but beautiful. The building is a very modern combination of glass, steel, concrete, and brick, set on the edge of a hill, where it projects an image of strength, stability, and beauty. The aesthetic beauty of thermodynamics results from the rigor of the discipline. Thermodynamics is one of the pre-eminent... 

The cell wall of S. cerevisiae, like that of other fungi, is very strong. Despite its great strength, one should remember that the cell wall is a dynamic structure (unlike a brick wall). There are three major components ... 

Silica bricks are manufactured from crushed ganister rock containing about 97 to 98 percent silica. A bond consisting of 2 percent lime is used, and the bricks are fired in periodic kilns at temperatures of 1,500 to 1,540°C (2,700 to 2,800°F) for several days until a stable volume is obtained. They are especially valuable when good strength is required at high temperatures. Superduty silica bricks are finding some use in the steel industry. They have a lowered alumina content and often a lowered porosity. 

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