Calcium limes

Limestone and marble have been mined as building materials and the oxide of calcium, lime [1305-78-8], has been used ia the manufacture of mortar for centuries (see Building materials, survey Lime and limestone). Lime-burning was one of the first iadustries ia the American colonies, where calcining of limestone was accompHshed ia kilns dug out of the sides of hills. 

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. 

With regard to chemical use -diluted ferric chloride solutions (10% to 20%) usually give better results in the conditioning of the sludge. A high calcium lime is preferable or sludge filtration work. One should avoid excessive use of chemicals. The quantities of chemicals used for conditioning can be frequently reduced by careful control of the... 

Z44 In every monovariant system there may be two modir-fications, the inverse of each other, which change the masses of the phases without changing their composition.— In certain monovariant systems only two modifications can be observed, the inverse of each other thus, in a system which encloses a liquid and its vapor, only the vaporization of the liquid or the condensation of the vapor in a system containing a solid and the liquid resulting from its fusion, only the fusion of the solid or the freezing of the liquid can be observed in a system containing carbonate of calcium, lime, and carbonic acid gas, one may observe only the combination of carbonic acid with lime or the dissociation of the carbonate of calcium. 

If young leaves are pale and growing tips die, the problem may be calcium deficiency. Add high-calcium lime, dolomitic lime if magnesium is also low, wood ashes, or gypsum to the soil. 

EN 12485 Chemicals used for treatment of water intended for human consumption — calcium carbonate, high-calcium lime and half-burnt dolomite — Test methods (in preparation). 

Nevertheless, it is believed that a significant quantity of high-calcium lime-stone/calcium carbonate is used for this purpose. A two-stage neutralisation process may offer the best overall economics. In the first stage, calcium carbonate is used to neutralise the greater part of the acid under acidic conditions. In the second stage, an alkali is used to neutralise the residual acid and to raise the pH to the required level. For more details of the chemistry involved, see section 28.3. 

Above the dissociation temperature of calciiun hydroxide (ca 540 °C), and below the dissociation temperature of calcite (ca 800 °C), equation (15.1) (see section 15.2.1) can proceed to the left with evolution of heat. Porous high-calcium limes can absorb over 50 % of the theoretical amount of CO2, whereas dense limes may only absorb 3 to 5 % of CO2 [15.8]. 

Average long-term values, for high calcium limes, excluding use for heating or drying fuel. 

Some very light-burned dolomitic limes are hydrated at atmospheric pressure in a similar way to high-calcium limes. They use maturing bunkers to provide 12 to 24 hours of residence at 80 to 90 °C in the presence of excess water. 

A wide variety of lime products have been used in lime treatment. In general, however, calcium limes are recommended [26.4, 26.5], which meet the requirements for building lime [26.18]. Dolomitic and hydraulic lime products are less suitable, as indicated below. 

The binder can be calcium lime, dolomitic lime, a hydraulic lime, a lime-cement mix, or cement. When calcium lime, or Type S dolomitic lime is mixed with sand to produce a sand-lime mortar, its initial role is that of a void filler. It subsequently causes the mortar to harden slowly, as a result of carbonation of the calcium hydroxide (N.B. when the term lime is used in connection with mortars, it refers to fully slaked lime with a low expansion potential. This includes Type S dolomitic times, which are widely used for mortars in the USA). 

Limes for building purposes are specified in CEN Standard EN 459 [26.18]. They are divided into the 8 groups listed in Table 26.7. Calcium limes (CL, which may be in the form of quicklime, powdered hydrated lime, or putty) are sub-divided into three - CL 90, CL 80 and CL 70 — on the basis of their chemical analysis. Dolomitic limes (DL) are sub-divided into DL 85 and DL 80, also on the basis of their chemical analysis. Hydraulic limes (HL) are described in section 26.9. 

Tables 27.3 and 27.4 summarise typical specifications for high-calcium lime [27.11] and calcined dolomite [27.12] used as fluxing agents in the BOS process. Both products should be ...

High-calcium limes, which include lump and pulverised quicklime, hydrated lime and milk of lime, are categorised in [28.3] into three Types (Table 28.1), depending on the levels of the major and minor components, namely ... 

Table 28.1. High-calcium lime for use in water treatment grading (proposed limits)...

Ground" refers to pulverised high-calcium quicklime, lump" refers to granular high-calcium quicklime, hydrate" refers to hydrated high-calcium lime and milk" refers to milks of lime % values are by mass. 

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