Highly soluble alkali-containing calcium

Highly Soluble Alkali-Containing Calcium Orthophosphates... 

The potassium or sodium aluminates dissolving in alkaline solution, are transformed in Al(OH)" ions [25], Due to the low permeability of concrete corrosion occurs slowly. Though the experiments show that that the rapid deterioration of calcium aluminate cement concrete occur at pH higher than 13, however, these concretes should not be used in environment of high pH. Aggregate containing soluble alkalis should also be avoided. 

Worldwide, there are no methods for the selective extraction of strontium from substrates containing high concentrations of calcium. An effective method for extraction of strontium from exhaust iodine-lwomine plants consists of the sequential sedimentation of alkali earth elements. For this purpose the solubility of a multi-component system such as Na, k, Mg Ca Sr // Cl, OH -H O Na K", Ca Sr " // Cl, -H O, was investigated... 

Soils that have been harmed by soluble salts are designated as saline or alkali soils. Saline soUs contain excess soluble salts only, whereas alkali soils are high in adsorbed sodium. The chief soluble salts are the chlorides and sulfates of calcium and magnesium either carbonates or bicarbonates and sometimes boron may be present. Extensive leaching with comparatively salt-free water may remove nearly all of the soluble salts from soils and make them suitable for crops, but sodium is held on the exchange complex, and this makes alkali soils very difficult to handle. 

Unlike Portland cement, hydrated aluminous cement pastes are resistant to diluted acid solutions with pH>4. This also includes natural waters containing dissolved CO2. One factor responsible for the good acid resistance of this cement is the absence of free calcium hydroxide among the formed hydrates, a phase that is easily soluble even in dilute acids. At the same time hydrous alumina is not dissolved at pH values down to 4. At very high pH values, such as those existing in alkah hydroxide solutions, corrosion of hardened aluminous cement may occur. Under these conditions AHj is dissolved in the liquid phase in the form of alkali aluminates. 

---