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| 6. - EFFLORESCENCES |
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"Efflorescences" are salt crystals, usually white, that lay on the surface of bricks, roof tiles and ceramic or concrete floors.
Although the efflorescence formation process is complex, we can simply say that some water-soluble salts can be transported by capillarity through porous materials and remain on the surface when water evaporates as a result of sunlight and/or air action (see fig. 4C).
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6.1. - Salts origin
a) Mortars and added materiales are the main source of salts and cause the apparition of most efflorescences.
b) Soil. The terrain can contain salts. Direct contact between terrain and walls or floors added to ground humidity is another frequent cause of efflorescences.
c) Construction elements. Bricks, floor and roof tiles could contain some salts. However, due to the chemical composition of raw materials used in the manufacturing processes and high temperatures of the processes themselves, these elements seldom cause efflorescences.
Nevertheless, as spots appear on bricks, roof or floor tiles surface, they are frequently and erroneously blamed to cause efflorescences.
6.2. - Water origin
a) Wind and rain make water go inside ceramic materials and mortars - thus dissolving salts.
b) Condensation water. Sometimes water results from inner condensation inside walls, in spite of insulation.
c) Water used in the work. In some locations, water can contain a high salts concentration.
d) The ground the construction is built upon is usually humid.
6.3. - Masonry or counter floor should not allow contact with sales and water
Design is important. Contact with salts and water is to be prevented by means of waterproof barriers, fissures and filtrations avoidance, etc.
6.4. - Efflorescences prevention
As a consequence of what has been explained above, contact among masonry, salts and water is to be avoided as long as possible.
We suggest you should follow these advises:
• Use mortars and waterproof material of acknowledged quality.
• If floors are positioned upon the ground, place a polyethylene layer between the ground and the counter floor in order to prevent steam from going through and humidity from condensing.
• In walls, take special care when you build the insulating layer.
6.5. - Efflorescences cleaning
You have to find out the causes of efflorescences before cleaning them up.
Some efflorescences are brushed once and they do not appear any more.
Sometimes just rain and time make them disappear. This happens when salts are contained in mortars, cement materials or ceramic pieces.
Another situation is when salts are found in the area's ground or water and there is no barrier impeding them emerging to the surface (v.g.: a basement brick wall in direct contact to the ground). In this case a more complex solution leading to impermeabilize the wall should be analyzed.
Washing is a simple way to clean up efflorescences. However, it should be done only in warm or dry weather. Otherwise water could dissolve more salts inside ceramic pieces.
Use of acid for cleaning is not advisable because acid can go through joints and affect the cohesion of bricks or floor tiles.
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DIMENSIONAL STABILITY (LESS MATERIAL MOVEMENT)
Most construction materials change their size as time passes due to humidity absorption, temperature variations and cargo action. These apparently light movements cause tensions inside materials and can eventually produce fissures.
Designs minimizing, accomodating or preventing these movements should be produced. Systems such as joints, fixations and steel reinforcements are usual solutions to these problems.
The thermal dilatation coefficient of red ceramics is nearly half of the concrete and plaster ones and a third of metals ratio.
After red ceramics are abundantly dampened before their positioning they do not change volume any more - although they can get dry or dampened again later. Other materials (v.g.: concrete) change their volume due to the humidity contained in them. Creep effect is irrelevant in red ceramics.
THE EXCELLENT DIMENSIONAL STABILITY OF RED CERAMICS MAKES SIMPLE, RESISTANT AND HARDLY REINFORCED CONSTRUCTIONS POSSIBLE!
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