Strength and the Conversion Reaction

The fall in strength has also been attributed to the formation of macrocrystalline alumina hydrate from the microcrystalline alumina hydrate. 

The hydration of CAC does not result in the formation of Ca(OH)2. This contributes to enhanced resistance in the presence of phenols, glycerols, sugars, etc. The formation of aluminum hydroxide gel during hydration provides resistance to dilute acids and sulfates. CAC has many industrial applications. It is used in flues, sewers, effluent-tanks, coal hoppers, ash sluices flues, and in industrial plants, e.g., oil refineries, breweries, dairies, and tanneries. 

CAC concretes are not resistant to alkali which readily attack the protective gels (possibly also iron-containing gels). The alkalis may also affect setting and strength development and accelerate the conversion reactions. 

CAC concretes are resistant to solutions containing dissolved CO2 and sea water. The formation of chloroaluminates is likely to affect the setting and hardening characteristics, and, therefore, the use of sea water as mix water should be avoided. 

CAC concretes can also be used to encapsulate amphoteric metals such as Pb, Al, and Zn due to reduced reaction between the hydrates formed and these materials. 

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