Lime hardening, 3.18

Synonyms Calcium abietate Calcium rosinate Limed rosin Rosin, lime-hardened... 

Rosin, lime-hardened. See Calcium resinate Rosin, methyl ester. See Methyl rosinate Rosin pentaerythritol ester. See Pentaer hrityl rosinate... 

The hardening of lime is a slow process called carbonation, which is based on the absorption of CO2 from the atmosphere when the lime hardens in the open air. The lime is then transformed again into limestone CaC03 and free water is evaporated. In thick brick walls the joints that are filled with lime mortar harden over several years. 

Hydrated lime is also used to stabilize the calcium sulfite—sulfate sludge derived from thickeners at SO2 scmbbing plants that use limestone—lime. Hydrated lime (2—3%) is added to react with the gypsum sludge and flyash or other added siHceous material. Under ambient conditions the lime and siHca serve as a binder by reacting as calcium siHcates so that the material hardens into a safe, nonleaching, stable, sanitary landfill or embankment fill. 

The reaction is completed after 6—8 h at 95°C volatiles, water, and some free phenol are removed by vacuum stripping up to 140—170°C. For resins requiring phenol in only trace amounts, such as epoxy hardeners, steam distillation or steam stripping may be used. Both water and free phenol affect the cure and final resin properties, which are monitored in routine quaHty control testing by gc. OxaHc acid (1—2 parts per 100 parts phenol) does not require neutralization because it decomposes to CO, CO2, and water furthermore, it produces milder reactions and low color. Sulfuric and sulfonic acids are strong catalysts and require neutralization with lime 0.1 parts of sulfuric acid per 100 parts of phenol are used. A continuous process for novolak resin production has been described (31,32). An alternative process for making novolaks without acid catalysis has also been reported (33), which uses a... 

Bone, or osseous tissue, is composed of osteocytes and osteoclasts embedded in a calcified matrix. Hard tissue consists of about 50% water and 50% solids. The solids are composed of cartilaginous material hardened with inorganic salts, such as calcium carbonate and phosphate of lime. 

A variety of materials has been proposed to modify the properties of asphaltic binders to enhance the properties of the mix (112), including fillers and fibers to reinforce the asphalt—aggregate mixture (114), sulfur to strengthen or harden the binder (115,116), polymers (98,117—121), mbber (122), epoxy—resin composites (123), antistripping agents (124), metal complexes (125,126), and lime (127,128). AH of these additives serve to improve the properties of the binder and, ultimately, the properties of the asphalt—aggregate mix. 

Morta.r, Mortar, principally slaked lime and sand, sets because of the evaporation of water, the deposition of calcium hydroxide, and the absorption of water by the bricks or cement blocks, foUowed by hardening as a result of the absorption and reaction of carbon dioxide. 

In the relatively small Pordand cement 2one almost all modem cements fall in the high lime portion (about 65% CaO). Cements of lower lime content tend to be slow in hardening and may show trouble from dusting of the clinker by transformation of to especially if clinker cooling is... 

Other Phases in Portland and Special Cements. In cements free lime, CaO, and periclase, MgO, hydrate to the hydroxides. The in situ reactions of larger particles of these phases can be rather slow and may not occur until the cement has hardened. These reactions then can cause deleterious expansions and even dismption of the concrete and the quantities of free CaO and MgO have to be limited. The soundness of the cement can be tested by the autoclave expansion test of Portiand cement ASTM C151 (24). 

Frieficements (83), manufactured in Belgium, are produced as a wet slurry of finely ground slag. When activators such as Pordand cement, lime, or sodium hydroxide are added in a concrete mixer, the slurry sets and hardens to produce concretes with good strength and durabiUty. 

Hydraulic limes (84) may be used for mortar, stucco, or the scratch coat for plaster. They harden slowly under water, whereas high calcium limes, after slaking with water, harden in air to form the carbonate but not under water at ordinary temperatures. However, at elevated temperatures achieved with steam curing, lime—silica sand mixtures do react to produce durable products such as sand—lime bricks. 

Basic materials such as lime or magnesium oxide increase the hardening rate of novolak-hexa compositions and are sometimes referred to as accelerators. They also function as neutralising agents for free phenols and other acidic bodies which cause sticking to, and staining of, moulds and compounding equipment. Such basic substances also act as hardeners for resol-based compositions. 

Kalk-haltigkeit, /, calcareousness, -harte, /. hardness due to lime, -harz, n. hardened rosin. 

Soliroc A process for solidifying aqueous wastes, converting them to a solid form suitable for landfill. The waste is initially acidic. Sodium silicate, cement, and lime are added, converting the liquid to a gel which hardens in several days. Used in France, Norway, Belgium, and Canada. 

Hatchett then investigated the composition of shell and bone. When it is applied to the cuttle-bone of the shops. . . , said he, the term bone is here misapplied. .. for this substance in composition is exactly similar to shell, and consists of various membranes hardened by carbonate of lime, without the smallest mixture of phosphate (8). 

Bases also have their domestic uses. The various kinds of soda found in the home - baking soda, washing soda and caustic soda - are all bases. But the widest used base of all is lime. Besides its agricultural use, lime is a vital ingredient in cement, mortar, plaster and concrete. The lime reacts with carbon dioxide in the air and hardens the mixture as it dries out. 

The primary industrial use of calcium metal is as an alloying agent to harden aluminum. Calcium compounds such as lime and gypsum are used for many purposes throughout the chemical and construction industries. Portland cement, for example, contains approximately 70% CaO. In addition, calcium is the primary constituent of teeth and bones. 

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