Hydration calcium formate

A diagram for one implementation of this process (61,62) is shown in Eigure 11. Recovered potassium sulfate is converted to potassium formate [590-29 ] by reaction with calcium formate [544-17-2] which is made by reacting hydrated lime, Ca(OH)2, and carbon monoxide. The potassium formate (mp 167°C), in hquid form, is recycled to the combustor at about 170°C. Sulfur is removed as soHd calcium sulfate by filtration and then disposed of (see... 

The way in which salts such as calcium chloride and calcium formate operate is not fully understood, but it is clear that the mechanism involves an acceleration of the C2S and C3S hydration. It has been proposed [23] that... 

It was stated that hydrated calcium monohydrogen phosphate in amorphous or cryptocrystalline form is a potential precursor in the formation of hydroxyapatite because the structural position of Ca2+ on (010) and (110) crystal planes of both minerals essentially correspond to one another492. These planes of calcium ions could easily serve as transition boundaries with little distortion of crystal structure the same holds true for octacalcium phosphate or defect apatites. Thus apatite may form from amorphous or microcrystalline calcium monohydrogen phosphate possible via octacalcium phosphate or defect apatites. This process may already start inside the matrix vesicles and continue during extravesicular activities. 

Francis, M. D., and Webb, N. C. Hydroxyapatite formation from a hydrated calcium monohydrogen phosphate precursor. Calc. Tiss. Res. 6, 335-342 (1971). 

The dry product is ground to a powder and then a little calcium sulfate (CaS04) is added to slow down the setting rate of the cement. When water is added to the mixture, slow complex chemical changes occur, resulting in the formation of a hard interlocking mass of crystals of hydrated calcium aluminate and silicate. 

The reactions occurring with calcium formate, nitrate and thiosulfate have not been widely studied, although it seems likely that calcium formate and thiosulfate [6] react with C A in a similar manner to calcium chloride to form C A3.Ca(HCOO). xH O and C A.Ca(S O ). yH O, respectively. In the case of calcium nitrale there is a difference m bdhaviour and the C A hydration is promoted to the cubic C AH form. 3... 

The way in which salts such as calcium chloride and calcium formate operate is not fully understood, but it is clear that the mechanism involves an acceleration of the C S and C S hydration. It has been proposed [23] that the initial products of cement hydration form a sort of membrane which acts as a restraint to the diffusion process which in turn leads to the dormancy period . It seems likely that the chloride ion, by virtue of its small size and high mobility, is able more easily to penetrate the pores of the restraining layer allowing the diffusion process to proceed more rapidly. The resultant tobermorite gel has a higher lime-silica ratio and a more open, accessible structure, based on a crumpled foil morphology rather than the usual spicular. The considerable reaction with,... 

Kano L, Yamashita H., Saito F. Effect of heat-assisted grinding of a calcium hydroxide - gibbsite mixture on formation of hydrated calcium alummate and its hydration behavior. Powder Technology 1998, 98 279-80. 

Francis MD, Web NC (1971) Hydroxylapatite formation from hydrated calcium monohydrogen phosphate precursor. Calc Tissue Res 6 335-342... 

Dicalcium phosphate dihydrate (CaHP04 2H2O, or hydrated calcium hydrogen-phosphate) is precipitated by reacting phosphoric acid with slaked lime. The reaction mixture is cooled to avoid the formation of the anhydrous phosphate [31.6]. 

It has been stated that water like ammonia can be added in two ways in the formation of addition compounds such a the hydrates, calcium chloride hexahydrate, etc., similar to the ammonia in the hexa-ammoniate of platinic chloride, PtCUGNHs. When platinic chloride is dissolved in water, the aqueous solution does not contain chloride ion as would be expected if the water combined with the chloride as the ammonia does. The platinic chloride combines with the... 

Carbonic acid formation decreases local pore solution pH from 14 to 8. This fall initiates passive hydrated ferric oxide film destruction and hydrated calcium carbonate formation ... 

According to Taylor [160] the mechanism of hydrated calcium silicate phases formation is strongly related to the properties of silicate anion substmcture. The SiO tetrahedra condensate simultaneously with the calcium-oxygen polyhedral, influencing on one another. Alternatively, the calcium-hydroxide layers can be formed firstly, and the condensation of SiO tetrahedra occurs on this matrix. 

The conditions of the calcium silicate hydrated phases formation given in Sect. 4.2.2 are of significant importance from the practical point of view. Depending on the temperature, time of theimal treatment, w/c ratio and the composition of initial mixture there are various intermediate phases produced. The reactivity of many phases, inert in relation to water, is markedly increased in the paste hydro-thermal treatment [216]. 

The chemical reactions of cement paste with zinc (galvanized steel) result in the release of zinc to the solution and the formation of calcium zincate, CaZn2(OH)g 2H2O, covering the surface of metal [49], Simultaneously, there is no portlandite crystals in this transition zone because in the presence of zinc alite hydration is delayed (see Sect. 4.1.3.2). The coating of hydrated calcium zincate crystals on the surface of metal increases the bonding forces between paste and reinforcement by the roughness formation on its surface. 

Simultaneously high cement content in concrete should be maintained, on the level of 400-450 kg/m [19], The curing of concrete could be performed at temperature close to 38 °C or higher, which assures the cubic hydrate direct formation, during calcium alrrminate cemerrt reaction with water [12]. This situation is well presented by the schematic strength development shown by Scrivener and Capmas [20] (Fig. 9.4). 

Erlenmeyer found that the butyl alcohol present in fusel oil yields iso-butyric acid (see below) on oxidation, and is therefore isobutyl alcohol, and he also showed that from isobutyl iodide the same valeric acid is obtained as from the amyl alcohol of fusel oil, which is therefore isoamyl alcohol, derived from dimethylethylmethane. Secondary butyl alcohol was first obtained as hydrate de butylene from erythritol by de Luynes. A. Lieben obtained it from zinc ethyl and dichloroethyl ether, and since he found that on oxidation it gives a ketone he recognised it as secondary butyl alcohol. Lieben and A. Rossi obtained normal butyl alcohol from butyric acid, which was converted into butyraldehyde by distilling calcium butyrate and calcium formate, and a solution of this reduced with a large amount of sodium amalgam. They give structural formulae for the four butyl alcohols, with the boiling-points. 

Calcium formate, of formula Ca(HCOO)2, is a by-product in the manufacture of polyhydric alcohol, pentaerthritol. It is a powder and has a solubility of about 15% in water at room temperature. It is a non-chloride chemical that is used in practice. Many non-chloride accelerating admixture formulations contain formates. Calcium formate is an accelerator for the hydration of C3S at equal concentration, however, CaCl2 is more effective (Fig. 

The rate of hydration of tricalcium silicate in the presence of different amounts of calcium formate (0.5%-6.0%) has been reported by Singh and Abha.i Calcium formate accelerates the tricalcium silicate hydration at 2% addition. It is speculated that in the presence of formate the protective layer on the silicate surface is ruptured, resulting in an acceleratory effect. 

The hydration of C2S is also accelerated by calcium formate. The increase in compressive strength of formate-treated dicalcium silicate samples in relation to the reference sample is evidence of an acceleratory effect (Fig. 

Bensted, J., Early Hydration Behaviour of Portland Cement in Water, Calcium Chloride and Calcium Formate Solutions, Silic. Ind., 45 67-69 (1980)... 

In the hydration of portland cement, although initially larger amounts of heat are developed in the presence of Ca formate, at later ages the heat may be slightly lower or equal to that of the reference material. Calcium formate accelerates the hydration of all types of cement. Figure 18 gives the relative amounts of heat produced by adding 0.18 molar calcium chloride, calcium nitrite, and ealeium formate to Type V cement. Calcium chloride is the best accelerator followed by calcium formate. ... 

Calcium nitrite has been used as a corrosion inhibitor in concrete. It accelerates the hydration of cement. In Fig. 18, its acceleration effect on Type V cement is obvious from the larger amoimt of heat developed compared to that by the reference.It appears to be a better accelerator than calcium formate. 

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