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Dissolved Matter
Published in Paul N. Cheremisinoff, Handbook of Water and Wastewater Treatment Technology, 2019
When the pure solvent freezes out of a solution, the concentration of the solute increases and the freezing point of the remaining solution is decreased. Further cooling causes more solvent to crystallize, and as the process continues, the freezing point becomes progressively lower as the concentration of the solute increases. The solution may eventually become saturated with the solute, for example, salt and water solution, and at this point further cooling causes both solvent and solute to crystallize out together in the same proportion as they are in solution. There is then no further change in concentration and hence no change in freezing point. The composition of a solution of such concentration, in which both solvent and solute freeze out together at a constant temperature, is called a eutectic mixture, and its freezing point is called the eutectic point. The eutectic point of a sodium chloride solution is −21°C. Below −21°C, salt added to ice will not cause it to melt, but calcium chloride can be employed, since the eutectic point of calcium chloride solution is −54°C.
Concrete
Published in Ash Ahmed, John Sturges, Materials Science in Construction: An Introduction, 2014
In the past calcium chloride was used as an accelerating admixture. It caused the concrete to gain strength more rapidly so that high-rise buildings could be built more quickly as the supporting formwork could be removed quickly. One serious side-effect of calcium chloride was that if included in sufficient quantities and if oxygen and water were present, reinforcement corrosion commenced. It is now banned, but many buildings still exist with calcium chloride included. Figure 12.7 indicates chloride profiles when salts have entered concrete from the surface and when chlorides were included in concrete during construction.
Deterioration mechanisms
Published in James Douglas, Bill Ransom, Understanding Building Failures, 2013
Manufactured materials may be used as additions to building materials, or as treatments for them, and may have an adverse effect on durability and performance, if not used with care and understanding. Calcium chloride is such a material and is commonly used as an accelerator of the hydration and development of the early strength of cement-based products, for example, mortar, concrete and wood wool. Its use has commercial advantages, in that it facilitates the early demoulding of precast elements and their removal from the factory production floor to storage and, also, the early striking of formwork from in situ concrete. However, it has a corrosive effect on metals and severe damage has been caused to reinforced concretes and to prestressed concrete through its use. This problem is considered in more detail in Chapter 10.
Effect of manganese salts on recovery of potassium from K-feldspar by means of a calcination reaction in the chloride salts-calcium carbonate system
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2023
Yu-Ling Shi, You-Fa Jiang, Cheng-Lin Liu, Jian-Guo Yu
At a calcination temperature of 800°C, calcium chloride is predominantly in a molten state due to its melting point of 782°C. When the temperature increases, the amount of molten calcium chloride increases resulting in improving the potassium extraction ratio. The decomposition rate of K-feldspar improves with an increase in the content of CaCl2 when the temperature and ratio of K-feldspar to CaCO3 are being kept constant at 800°C. With the portion of CaCl2 increases, Zhong et al. (2016) found that the extraction increased gradually and stabilized as the ratio of KAS6:CaCl2 achieved 1:2.5, but a different result observed in this study can be explained by the adhesion occurred between the reactant and porcelain boat which causes difficulties in the pulverization of slags calcined and leads to a decrease in the potassium extraction at 900°C.