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The Friable structure of hydroaluminates worsens frost resistance, and also firmness against chemical corrosion. It is one of the reasons of restriction of quantity trehkaltsievogo aluminate in special portlandtsementah, applied to cold-resistant concrete. мас моторс автосалон отзывы
The Stable form - the six-water hydroaluminate crystallising in the cubic form, is formed as a result of quickly proceeding chemical reaction.
For delay shvatyvanija at a grinding klinkera add a small amount of natural plaster (3-5% from weight of cement). Calcium sulphate plays a role of chemically active component of the cement reacting with trehkaltsievym by aluminate and connecting it in gidrosulfoaljuminat of calcium (a mineral ettringit) in the hydration beginning portlandtsementa
.v the sated solution of Sa (IT) 2 ettringit at first is allocated in kolloidnom tonkodispersnom a condition, being besieged on a surface of particles, slows down their hydration and delays the beginning shvatyvanija cement. Crystallisation from peresyshchennogo a solution lowers concentration gidrookisi calcium in a solution, and ettringit is already formed in the form of long iglopodobnyh crystals. Crystals ettringita also cause early durability of the hardened cement. Ettringit, containing 31-32 molecules kristallizatsionnoj waters, occupy approximately twice bolshy volume in comparison with the sum of volumes of reacting substances (РЎ3Рђ and calcium sulphate). Filling a time of a cement stone, ettringit raises its mechanical durability and firmness.
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