(1),hydration gelatin type
After the cement hydration, it's primary product has the alkali - silicic acid gelatinous matter and so on. The natural stone micropore's capillarity causes the gelatin class to migrate along with the surface water volatility to the surface layer and coagulates.
The cement gelatinous matter is level (net) shape structure, its surface achieves to the area 200~600㎡/g, the gelatin hole's size is 1.5~3nm, is only a number magnitude bigger than the Water molecules, has very strong hygroscopicity, moreover, with method of simple heating cannot cause these gelatinous matter to be decomposed. Adsorb with the moisture, the gelatinous matter present to be translucent shape, causes the change of light reflection index, glanced at it, is looks like that the stone is been moist by the water.
When the stone not so density use the method of direct aqueous glue, often will have this kind of water stain to appear.
(2),water absorbability salt alkali type
it include high salt alkaloid contained in cement and also the Soluble salt alkaloid kind of absorption of moisture which the cement additive bring itself, These salt alkaloid kind of absorption of moisture is extremely easy to take up water, forms the hydrate to produce the water stain. When serious it may also cause the stone surface to present the obvious salty alkaline spots.
A,In the cement aggregate itself brings salt alkaloid: the oxide compound in the cement fine aggregate including Na2O, K2O and so on, its alkali content is 0.6~1.5%, after water mix, it produces NaOH, KOH this kind of water-soluble alkali etc. a Part react with active silicon dioxide (SiO2) and in the aggregate and form alkali - silicic acid gelatinous matter, a part react with calcite powder in aggregate and produce sodium carbonate and the calcium hydroxide and so on, unnecessary part will separate out from the stone pore.
B,the use of cement admixture bring soluble salt alkaloid the kind of absorbing moisture: like NaCl (antifreeze), CaCl2 (early strength agent), triethanolamine (early strength agent) and so on in cement admixture.
In actual situation, often water stain formation is not sole type, what is most common is the hydration gelatin and the water absorbability salt alkaloid supplement each other, because the easy deliquescence salt alkaloid having the low steam pressure, they will adsorb in the air the moisture content until to achieve balanced which presses with the outside steam, but the stone micropore and the hydration gelatinous produces the additional pressure (pore capillarity phenomena) which enable the balance to be more advantageous in adsorbs more moisture contents, therefore no matter what the outside weather like, the stone surface layer's water always is very difficult to dry. Because the water absorbability salt alkaloid is being wrapped by the gelatinous matter, if wants to clean this kind of water stain it is not soeasy.
As for the construction decoration stone , the water is the root of all evils, after the stone forms the water stain, often other illness also one after another will appear, like water stain, water stain + rusty stain and so on.
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