Inside the room, on a brick wall, dark joints are marked between the wall blocks.
What is a cause of it?
There are so-called. thermal bridges. Due to the insufficient thermal insulation properties of the wall, mortar joints are visible on it. Due to the increased heat transfer through the joints and the strong diffusion of water vapor, more dust is deposited in these places.
The dried-up water stain on the plastered ceiling has visible yellow-brown fringes. What could be their cause? The water penetrating the plaster washed away the soluble iron salts from the mortar sand, which, along with water, got to the surface of the plaster layer. The water evaporated, and the iron salts remained as colored fringes.
What salts appear in the form of efflorescence on plaster?
Carbonates appear in the form of efflorescence, sulfur, nitrates and chlorides. Chlorides show up as wet spots, because these salts are highly hygroscopic.
How sulphate effluents are formed due to environmental pollution?
Sulfur dioxide is formed in the polluted air (SO2), oxidizing to sulfur trioxide (SO3), which, when combined with water, forms sulfuric acid (H2SO4). Because sulfuric acid is stronger than the carbonic acid contained in the plaster binder, the latter is displaced from calcium carbonate and sulphate is formed. Sulphates can also precipitate from capillary-pulled groundwater with insufficient horizontal insulation; they can also arise during the firing of the binder.
What effects on plaster can the presence of sulfates cause?? Sulfates are easily soluble in water, thus it is possible to decompose the binder, which in turn leads to a decrease in the strength of the plaster.
Sulphates may crystallize as efflorescence. Plaster spattering is possible due to the stresses caused by the hydration and crystallization of the salt.
Please describe the effect of chlorides on plasters. Chlorides are strongly hygroscopic (hydrofilowe). Therefore, in plasters containing them, light moist spots appear in high air humidity. Otherwise, plaster may fall off due to stresses caused by hydration and crystallization.
Please explain, how dangerous-looking nitrate blooms can appear on plasters.
Nitrates are formed in livestock buildings, in which nitrogen-containing compounds are released (ammonia and urea). These compounds, in combination with oxygen, act on calcium-containing materials according to the following reaction:
That(OH)2 + 2NH3 + 4THE2 → Ca(N03)2 • 4H2THE
hydroxide + ammonia + oxygen = hydrated calcium nitrate
Strong blooms appear on the plastered facade.
How can you confidently determine their nature?
1. Evidence of carbonates:
The grated mass of plaster containing efflorescence should be mixed with a 10% solution of hydrochloric acid.. If there are carbonates in the plaster, as a result of a strong reaction (effervescence) carbon dioxide will be released as an odorless gas.
2. Evidence for the presence of chlorides, sulfates and nitrates:
These salts can be identified by various indicators, available at chemical reagent stores. Usually, these indicators also make it possible to determine the concentration of these salts. The second option is to conduct a chemical analysis.