Silicate calcium

Silicates at about 20-40 p.p.m. are also used in cooling-water treatment although the build-up of protection can be slow. At higher temperatures calcium silicate may be deposited from hard waters. 

Calcium Silicate Brick. Sand—lime brick is used ia masonry ia the same way as common clay brick. The bricks, molded from a wet mixture of sand and high calcium hydrated lime, are heated under pressure ia a steam atmosphere. Complex hydrosiUcates are formed that give the bricks high dimensional stabiUty (6). 

Calcium Silicates. Cements aie hydiated at elevated tempeiatuies foi the commercial manufacture of concrete products. Using low pressure steam curing or hydrothermal treatment above 100°C at pressures above atmospheric, the products formed from calcium siUcates are often the same as the hydrates formed from their oxide constituents. Hence lime and siUca ate ftequendy used in various proportions with or without Portland cement in the manufacture of calcium siUcate hydrate products. Some of these compounds are Hsted in Table 6. 

Calcium silicate Foam glass Mineral wool 

Table 6. Calcium Silicate Hydrates Formed at Elevated Temperatures

Aluminum-jacketed calcium silicate insulation with an emissivity factor of 0.05. To convert inches to miUimeters, multiply by 25.4, to convert dollars per 1 miUion British thermal units to dollars per 1 nulhon kilojoules, multiply by 0.948, = 5/9 ( F — 32). 

L.F. Insulate 4" pipe and fit with calcium silicate, V thick, alum fin. 53.0 

Boron carbide from boron oxide and carbon Calcium silicate from lime and silica Calcium carbide by reaction of lime and carbon Leblanc soda ash 

Some commonly used insulating materials are calcium silicate, mineral slagwool, glass fiber, cellular glass, and polyurethane. 

The calcium oxide formed reacts with impurities in the iron ore to form a glassy material called slag. The main reaction is with Si02 to form calcium silicate, CaSi03  

AfwiUite can also be formed, and appears to be the thermodynamically stable calcium silicate hydrate in pure systems, at room temperature. 

Assume a 3-in. line. Design process temperature 320°F (Tp). Insulation 1 V2 -in- thick calcium silicate. Steam temperature 366°F (TJ. Ambient temperature 0°F (L,). 

Brunauer and co-workers [129, 130] found values of of 1310, 1180, and 386 ergs/cm for CaO, Ca(OH)2 and tobermorite (a calcium silicate hydrate). Jura and Garland [131] reported a value of 1040 ergs/cm for magnesium oxide. Patterson and coworkers [132] used fractionated sodium chloride particles prepared by a volatilization method to find that the surface contribution to the low-temperature heat capacity varied approximately in proportion to the area determined by gas adsorption. Questions of equilibrium arise in these and adsorption studies on finely divided surfaces as discussed in Section X-3. 

Ca +, Fe + etc. which are the cationic species in the slag phase). Fellner and Krohn (1969) have shown that the removal of phosphorus from iron-calcium silicate slags is accurately described by the Flood-Grjotheim equation widr 

Cements are commonly made by heating a mixture of limestone and clay to about 1700 C. The product is ground with gypsum. Chemically cements consist of a mixture of calcium silicates and aluminates with some sulphate present. World production 1976 730 megatonnes. 

Recommended Thickness of Insulation Indoor insulation thickness appears in Table II-2I, and outdoor thickness appears in Table 11-22. These selections were based upon calcium silicate insulation with a suitable aluminum jacket. However, the variation in thickness for fiberglass, cellular glass, and rockwool is minimal. Fiberglass is available for maximum temperatures of 260, 343, and 454°C ( 500, 650, and 850°F). Rock wool, cellular glass, and calcium sihcate are used up to 649°C (I200°F). 

For equivalent particle size the carbon blacks are the most powerful reinforcing fillers. However, fine particle size silicas can be very useful in non-black compounds whilst other fillers such as aluminium hydroxide, zinc oxide and calcium silicate have some reinforcing effect. 

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