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Purity and identification of grey calcium powder, core material of water-resistant putty (simple method)

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[Abstract]:
You may think that gray calcium powder (commonly known as "hydrated lime") why to emphasize a single "pure" word, I will discuss this with you in detail in the following.

First of all, let's talk abo
You may think that gray calcium powder (commonly known as "hydrated lime") why to emphasize a single "pure" word, I will discuss this with you in detail in the following.
 
First of all, let's talk about the origin of gray calcium powder. China is rich in limestone resources, but the difference is only in purity. Hebei, henan, zhejiang, guangxi, hubei and other provinces are all produced.   
 
Different equipment technology, different raw materials, so the quality and performance of gray calcium is not the same.   
 
 
 
The raw material of gray calcium is limestone (main component calcium carbonate, molecular weight of 100), calcined into quicklime (main component calcium oxide, molecular weight of 56) and then
 
The lime is then digested with water and matured (calcium hydroxide, main component, molecular weight 74).
 
 
 
Calcium hydroxide is a kind of high activity gas rigid cementitious material, which can react with carbon dioxide in the air to produce calcium carbonate under wetting conditions.
 
Thus increasing the surface strength. If be used with Portland cement collocation, also can promote cement hydration, so say ash calcium powder is used good it is a kind of very good raw material.
 
 
 
The appropriate amount of water resistant putty in the external wall can promote the hydration of cement, greatly improve the hardness of the surface, plus is the gas rigid material, so the later strength will continue to increase.
 
Pure gray calcium powder in the cup mixed with water into a paste, the state as butter, very smooth, so it can also improve the feel of putty, putty batch scraping smooth.
 
 
 
It is also the main cementitious material of water - resistant putty; Because of the addition of gray calcium, itself is alkaline material, so also can prevent mildew.
 
Before the invention of putty, the old grandparents whitewashed the wall with hydrated lime, which is absolutely environmentally friendly without any VOC.
 
 
 
In the water-resistant putty on the inner wall, we should use high-calcium gray calcium powder instead of high-magnesium gray calcium powder, because the carbonate is also formed,
 
But calcium carbonate belongs to insoluble carbonate in water, while magnesium carbonate belongs to slightly soluble carbonate in water, so you can see the difference in water resistance.
 
(we also measured the difference in water resistance strength is relatively large) (magnesium ash and calcium ash mainly depends on the raw stone, the price of magnesium ash is also cheaper than calcium ash!)
 
 
 
The whiteness of magnesium gray calcium powder is higher than that of calcium gray calcium powder, and the whiteness can even reach 92-93, and feel smoother than that of calcium gray powder,
 
The whiteness of high calcium ash is around 85-90. It is better to use high calcium ash in water - resistant putty.
 
 
 
Above mentioned a word "pure", this is very critical, mentioned above three materials, can be converted into each other, and the appearance of similar,
 
Driven by the interests, in order to compete at a low price, many use gray calcium powder + heavy calcium powder to disguise as pure gray calcium to sell, thus,
 
It will greatly increase the comprehensive cost for the downstream customers (increase the dosage to increase the direct cost, coupled with increased logistics cost, transportation cost and a series of costs) and the utility is far lower than the pure gray calcium.
 
 
 
After gray calcium powder adulterates, admixture increases greatly, and feel bad also, if the digestion of gray calcium powder is not complete, calcium oxide will exceed the standard, after the wall, the first may dry fast, thickening severe, the most serious is the wall blasting ash pit.
 
As shown in figure:
 
 
 
We have tested a lot of gray calcium, with different purity, most of which are 40-60%. The above results were measured in wacker laboratory (manufacturers are not allowed to make them public).
 
Application of gray calcium powder in water-resistant putty: ordinary water-resistant putty putty content in the inner wall of 100-150 kg/ton finished putty.
 
Of course, if your dosage is very high also dedusting, it may be: 1. Gray calcium impure, 2.
 
Grey calcium purchased can be self-tested with density: generally 400-600 g/l. Buy a standard volume liter.
 
The main method is to mix heavy calcium into gray calcium powder. The settlement volume is simple and direct. It is not only qualitative, but also quantitative. The volume of ash calcium deposition was about 1.70-1.75ml/g, and that of heavy calcium was between 1.00 and 1.10. The closer the volume of calcium deposition is to the former, the higher the purity is, and vice versa. If the settling volume of gray calcium is only 1.12ml/g, it can only be called gray calcium mixed with heavy calcium, and its mass can be considered. Ash calcium settlement volume is 1.7ml/g, so the quality is good. I use this method repeatedly, effectively put an end to the interference of fake goods. Specific method: spend a few yuan to buy a 50ml measuring cup, add 30ml of water to the cup, then add 20g of gray calcium to be measured, one hour later to see how gray calcium settlement to scale. If it sinks to 25ml, divided by 20g, the settlement volume is 1.25ml/g, and it is preliminarily judged that this gray calcium has been mixed with heavy calcium by about 30%. Generally, the settlement volume should be greater than 1.35ml/g.
 
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