Clay bricks

Deflocculation and Slurry Thinning. Sihcates are used as deflocculants, ie, agents that maintain high sohds slurry viscosities at increased sohds concentrations. Soluble sihcates suppress the formation of ordered stmctures within clay slurries that creates resistance to viscous flow within the various sytems. Laboratory trials are necessary, because the complexity of the systems precludes the use of a universal deflocculant. Sihcates are employed in thinning of limestone or clay slurries used in the wet-process manufacture of cements and bricks, clay refining, and petroleum drilling muds (see also... 

Ziegel-erde, /. brick earth, brick clay, -erz, n. tile ore. -fachwerk, n. brick checkerwork. -farbe, /. brick color, brick-red. 

Ziegel-sorte, /. grade or sort of brick or tile, -stein, m. brick, -ton,/, brick clay, tile clay. 

Brick clays (plastic, containing iron oxide)... 

In the drying of materials such as wood or clay, the moisture concentration at the end of the constant rate period is not uniform, and is more nearly parabolic. Sherwood has presented an analysis for this case, and has given experimental values for the drying of brick clay. 

Kaolinite (theor.) Kaolin (washed) Refractory day (fireclay) Earthenware Stoneware clay clay Brick clay... 

Borosilicate glass, 60, 63, 203—207 Breunnerite, 378 Brick clay, 34, 313 Brickmaking, 313 — 314 Brookite, 21 Bubble drilling, 368 Bulk density, 291 Bushing, 162... 

A temperature resistant binder is necessary to bond SiC-bricks (carborundum bricks). Clays or other silicates are usually used, the particles being bonded by a glass phase. The bricks must be fired at ca. 1500°C in an oxidizing atmo.sphere to reduce the reduction of bonding clay to silicon and thereby prevent the bricks becoming brittle. The resulting oxidation of silicon carbide is limited by the formation of a passivation layer of Si02 on the SiC particles. 

Chrome brick Clay Coal tar oils Coal tars Coke... 

Brick clays tend to be high in alkalis and iron, but low in alumina [14], The clays usually have moderate to high plasticity, which facilitates forming [25], Often, brick clays are actually shales [14], These clays fire at moderate temperatures (cone 1-5) and the resulting fired bodies are dark red. Clays with similar properties but different colors upon firing can be used to produce other products such as sewer tile and roofing tile [6], Nearly any red burning clay can be classified as brick clay. 

Salt crystals, rock salt, sand, wool Brick clay, kaolin, crushed sand Pigments, paper, soil, worsted wool fabric Several foods, copper carbonate, sludges Chrome leather, vegetables, fruits, gelatin, gels... 

The kaolin group includes kaolinite, nacrite, dickite and halloysite halloysite can also exist in a hydrated form having the formula Al2Si205(0H)4.2H20. Of all these, by far the most important is kaolinite, since it is the principal constituent of china clay, ball clay, fireclays, and many brick clays the other kaolin minerals are somewhat rare in Britain. 

Fortunately this description covers most of the commonly-used British clays—ball clays, fireclays, china clays and some brick-clays. For clays containing a montmorillonite or a chlorite, rational analysis presents a much more difficult problem, requiring special analytical methods. 

Fireclays are extracted by open-pit methods, as described for brick-clays. If the seam is a deep one, and sufficiently valuable, it may be extracted by deep mining, as for coal, particularly if the coal can be extracted at the same time. 

Since brick-clays constitute a great variety of sedimentary deposits, ranging from the Devonian to the Recent Period of geolo-... 

The principal minerals in brick-clays are kaolinite and chlorite, with illite, quartz, and organic matter many brick-clays contain considerable amounts of iron oxide and calcium carbonate. Because the composition of the minerals, particularly chlorite, is uncertain, it is difficult to calculate a rational analysis for brick-clays, as has been done for ball clays. 

Some of the more important properties of some brick-clays are given in Table 16. 

The size distribution of particles in brick-clays ranges from 2.5 mm. down to 2fx but, as pointed out under ball clays, it is the distribution of particles below 2(jl that is the most important. The values in Table 16 refer to the latter size, which is usually said to consist entirely of clay this is not strictly true, because some nonclay impurities as small as this do exist, but identification of the less than 2 l range with clay is a fair approximation. 

The response of a brick-clay to deflocculants is of little technological interest, since such clays are not cast deflocculants are used, however, in determining the size distribution by sedimentation methods, and it is of interest that, for the Etruria Marls, a mixture of 5 parts by weight of Calgon to 1 part of NaOH was a more effective deflocculant than sodium oxalate. All the other clays mentioned were deflocculated well with this mixture. This behaviour is probably related to the exchangeable ions of the clays. 

Since the oxides of sodium, potassium, calcium and magnesium act as fluxes and promote vitrification, brick clays containing a good deal of CaCOg are readily fusible, and have to be fired at a comparatively low temperature for building-bricks the range of firing-temperatures is from 950° to 1200°C. 

Brick-clays are mostly extracted in open workings, but if they outcrop on the side of a hill, with an extensive overburden, the most convenient method is to tunnel into the side of the hill at the level of the seam (drift or tunnel-mining). If the seam is not more than 20 ft. below the surface, the overburden is stripped off by means of skimmers, power shovels, bulldozers or shovel-dozers, and the underlying clay is removed with a dragline scraper or skimmer (Figure 31). Sometimes shallow pits are dug out and the clay is stripped from the sides of the pit with a bucket-type mechanical excavator (Figure 32) or a shale planer (Figure 33). 

Table 16 Physical Properties of some Brick-clays... 

Fillipi C (1980) Lamination in Clay Extrusion - Causes and Correction. Part I Clay Mineralogy provides the first clue to lamination. J Brick Clay Record vol 177 No 8 pp 28-30... 

Seanor JG (1963) Laminations - Causes and Cures. Part I What causes them in clay products J Brick Clay Record vol 142 No 4 pp 80-81, 113-114... 

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