Efflorescence: The Definitive Guide to Pathology (2024)

Now, more technically...

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We know that efflorescences are whitish deposits that form when the substrate comes into contact with water, but how does this process take place?

First of all, we have to understand that the main cause of efflorescence in brickwork is the presence of free lime on any substrates that include cement in the composition, such as laying mortars, which are placed on the sides, plastering, Chapisco and concrete blocks.

This is because cement contains the chemical compounds calcium hydroxides and magnesium hydroxides, which when they react with carbon dioxide in the air, are transformed into free lime, a process called carbonation. The chemical reaction that explains this is the so-called “Free Lime cure”, which can be:

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Calcium Hydroxide + Carbon Gas from Air → Calcium Carbonate (or “Free Lime”) + Water

or

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Magnesium Hydroxide + Carbon Gas from Air → Magnesium Carbonate (or “Free Lime”) + Water

So, the initial condition for efflorescence to appear is the existence of free lime and it is found in everything containing cement. Therefore, it is good to be aware because the range of surfaces that can be affected by this pathology is enormous, although there are some prevalence rates that we will explain later!

Thus, when free lime comes into contact with water, whether it comes from rain, from wells, washes, or any other sources, the dissolution of the free lime occurs. This solution, due to different levels of salt concentration, migrates, through an osmotic process, to the surface and the evaporation of water results in the formation of whitish salt deposits, the so-called efflorescence. It was easy, wasn't it?

So, now let's understand other processes that, many times, people confuse with efflorescence, but they are not the same thing, although there is a relationship between them. To clear up confusion and answer questions, read the next topics!

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Efflorescence or Carbonation?

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Since we've talked a bit about efflorescence, how about knowing a little more about carbonation, which I mentioned earlier through chemical equations?

There, I showed that calcium or magnesium hydroxides present inside the concrete or that have been leached to its surface undergo a process when they react with carbon dioxide in the air, forming calcium or magnesium carbonates, salts soluble in water.

In the case of concrete, which has a high pH (alkaline), this reaction lowers its pH significantly, making it more acidic, leaving the reinforcements more exposed and susceptible to corrosion.

I'll explain it to you in more detail, follow along with me. After the calcium or magnesium hydroxides react with CO2 in the air, carbonates, Ca (CO) 3 or Mg (CO) 3, precipitate, and a layer with lower alkalinity of the area that did not undergo the reaction is formed.

Thus, carbonation advances from outside to inside the concrete and when it reaches the depth of the reinforcements (hardware), the corrosive process begins. The first signs of carbonation are manifested by white deposits on the concrete surface and are more evident when cracks appear and the dislocation of the coating layer.

In addition to the corrosive process that the concrete hardware will undergo, over the years, there will be a volumetric expansion of the affected point, increasing the size of the crack, crack or “bug”, which will contribute to the degradation of the concrete. If you want to know more, keep reading, and I'm going to do a chemical analysis about it.

When we think about molecular weight, we have:

Ca (OH) 2 = 74 grams/mol
Ca (CO) 3 = 100 grams/mol

This means that when calcium hydroxide reacts with carbon dioxide, through the carbonation reaction, resulting in calcium carbonate, we can notice an increase of more than 35% in mass and, consequently, in volume.

As two bodies do not occupy the same place in space at the same time, successive microexpansions will occur in the concrete at this location, leading to the degradation of the system.

You may have seen concrete undergoing this corrosion process, as it is very common, but know that prevention is very simple! Concrete carbonation is more frequent in regions with relative air humidity and higher temperatures, regions with a high concentration of CO2, among other factors, and is aggravated by the higher incidence of these factors.

Then, if done correctly, waterproofing helps combat carbonation and the corrosive process of concrete reinforcements, since keeping the covering layer intact and with low permeability and, consequently, high alkalinity, promotes better protection for the reinforcements against corrosion.

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Efflorescence or Leaching?

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Leaching: What does it have to do with efflorescence? You may not be familiar with this term, but I'm sure you know what I'm talking about! Leaching is part of the process of efflorescence, because it consists of the accumulation of calcium hydroxide on the surface.

But how does that happen? A leaching It is the phenomenon of water entering the concrete, dissolving the Ca (OH) 2 and Mg (OH) 2, present in the cement, and bringing them to the surface.

When on the surface, calcium and magnesium hydroxides react with CO2 in the air, undergoing the carbonation reaction, becoming salts, which, with the evaporation of water, form the white spots that we call efflorescence. In other words, leaching makes it possible for efflorescence to occur.

In addition, the entry of water through concrete, leaching, can cause more serious problems for concrete pieces, such as reduced mechanical strength due to the loss of solids in the concrete, in addition to opening paths for the entry of harmful substances to the reinforcements and to the concrete itself. Therefore, the ingress of water through the concrete can cause concrete failures (“bugs”), cracks, cracks, cracks, openings caused by the lack of hydration in the curing process, leading to a loss of mass, oxidation of the hardware and future loss of mechanical properties.

Did you stop to think that if we avoid the occurrence of leaching in concrete, we are also preventing the onset of efflorescence? This is because without the hydroxides on the surface, the carbonation reaction is not possible and thus, the salts, essential for the appearance of efflorescence, are not formed.

If we prevent the occurrence of leaching in concrete, we will also be preventing the appearance of efflorescence

And how to create a barrier so that the leaching process does not happen? For the salts to dissolve, it is necessary for the concrete to have contact with water, so avoiding the penetration of water is already sufficient to block the development of the process, thus also preventing efflorescence. And how to prevent the passage of water, you know, right? There's no secret: it's just waterproofing the right way! I'll tell you how to do it later!

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Factors for the Emergence of Efflorescence

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I think it has already been possible to understand which factors that cause the appearance of efflorescence, but now, I will summarize everything in this topic to make it easier to understand.

Since efflorescence occurs due to the dissolution of salts in water, which, when evaporating, form whitish deposits, do you agree that preventing contact of water with the surface would prevent this pathology?

If there is no water available, the salts will not dissolve and, therefore, the salt deposits and whitish spots will not appear. Is it that simple? YES!

Oddly enough, preventing the contact of water or moisture on the surface prevents efflorescence!

But if you've ever heard that there are other causes, let's go! I will explain a bit about the best known, but note that in all of them, the problem is closely related to the contact of the surface with water or moisture:

• Excess water: a greater amount of water in contact with the substrate facilitates the transport of salts to the surface;
• Materials with a high content of soluble salts: materials that have more calcium and magnesium hydroxides in their composition are more likely to develop efflorescence. Therefore, it is more recommended to use CP III and CP IV cements, which have a lower concentration of hydroxides, reducing the occurrence of the pathology;
• Hot and humid environment: moisture is water vapor, which can penetrate the surface, making it possible for salts to dissolve, and the high temperature works as a catalyst to accelerate reactions;
• Impurities in sand: if the sand used to prepare the concrete contains impurities, it can make the material more porous, which makes it easier to transport soluble salts through water;
• Cracks in the grout: The fissures are not grout they are empty spaces that facilitate the penetration of water into the concrete, making efflorescence more likely. That's why it's important to cover any cracks as soon as possible.
• Expansion joints: as well as in cracks in the grout, if there are flaws in the sealing of expansion joints or seals compromised due to lack of maintenance, infiltration will occur. So sealing expansion joints are also super important.

These were some examples of factors causing efflorescence, but there are many others, since anything that facilitates the contact of water with the material can be a determining factor for the onset of the pathology. Therefore, as long as the passage of moisture and contact with water does not cease, the appearance of efflorescence will remain.

as long as the passage of moisture and contact with water does not cease, the appearance of efflorescence will remain

So, to block the passage of water or moisture to a substrate, there is nothing better than using a suitable waterproofing agent. That's what I'm going to talk about in the next topic!

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How to Stop Efflorescence?

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As I just said, the best thing to do is waterproof the surface that is susceptible to efflorescence, that is, materials that contain calcium and magnesium hydroxides in the composition, such as mortars, ceramic and concrete blocks, grouts, and floors.

By preventing the passage of water or moisture, the entire process of pathology formation is broken right from the start. Therefore, waterproofing, in addition to being a very simple procedure, also helps to clean and conserve the material, keeping the aesthetics impeccable and with low maintenance requirements.

With that in mind, Blok developed countless waterproofing agents which are highly recommended to prevent the appearance of efflorescence, in addition to contributing to easier cleaning, long-lasting conservation and low maintenance costs. Therefore, avoiding this pathology is simpler than you imagined, isn't it?

But what if you didn't do the waterproofing in the correct way and did those white spots appear? And now? Is there a solution? Rest assured because I say yes!

Blok came out ahead and also thought about how to solve the areas already affected by efflorescence! Do you want to know how?

O Blok Eflohard It is a product with immediate action to combat efflorescence present in mortars and concrete, since it is a converter that reacts with the free lime present in the affected substrates, transforming the efflorescence into hardened compounds, eliminating the pathology.

It is good to make it clear that when using Blok Eflohard, the efflorescence will disappear, but if there is still contact with water or moisture and the surface is not waterproofed, the appearance of efflorescence will remain.

And if the efflorescences are not converted with the right product, more serious pathologies may appear. Therefore, we strongly recommend applying a suitable waterproofing agent as soon as possible to avoid having to deal with this problem, right?

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Check Out Some Examples and See If Your Case Fits Any of Them:

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Now, I've separated some examples I found of efflorescence on buildings. Note that they are everywhere and that they are easily identified on various types of substrates.

It also repairs the aesthetic damage they bring, deteriorating and degrading the material. Therefore, read what I prepared to understand more on a case-by-case basis. Of course, each case must be analyzed and treated considering its specificities, but here you will have a good idea of how this common pathology is manifested in various types of coatings. Are you ready?

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Efflorescence in Concrete

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Since the concrete block has a chemical composition that is much closer to the laying mortar, the migration of chemical compounds to the blocks is lower, which indicates that the probability of efflorescence occurring in ceramic blocks is much higher. Despite this, there are many cases of efflorescence on concrete blocks, manifested in a very accelerated and intense manner. That's what we'll see next.

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In this image, we have a brickwork settlement with cement and sand-based mortar. This mortar is rich in cement, which means that it has more free lime than the concrete block itself, and is more susceptible to the occurrence of the pathology.

We see here a classic example where the laying mortar is providing free lime to the concrete block and, on its left side, there is a degradation of the laying mortar. It is possible to verify that there is a failure of waterproofing system and clay is already passing through the spots where the mortar has degraded the most.

We can also observe that the shapes of the efflorescences always culminate close to the settlement mortar and, in some blocks, moving more towards the center. Logically, it is proof that efflorescence always starts from the settling mortar to the inside of the block wall.

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Here, we have a brickwork made of concrete block with a mortar rich in cement. The efflorescence came out of the settlement mortar and side rubbing, passed into the block and crossed the terracotta-colored acrylic paint, managing to make micro-holes and surpass the paint. At some points it has already degraded the paint and the most superficial layer of the block, leaving it more rustic than normal because of the loss of mass of the concrete block. This proves that efflorescence can even surpass paint, displacing it or not.

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Again, we have a brickwork made of concrete blocks with a mortar rich in cement. This mortar, subject to humid conditions, is solubilizing free lime (calcium hydroxide and magnesium hydroxide), transmitting it in every direction to the concrete blocks. We also see an accumulation of calcium and magnesium carbonates, which would be the cured products of hydroxides, which were leached and solubilized by the passage of water from inside to outside. It is also possible to verify the beginning of the degradation of the chemical composition of the laying mortar and lateral rubbing, with flaws and holes already appearing on their surface.

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In this image, we can see a brickwork built with concrete blocks with a mortar rich in cement, moisture through the inner side of the building and the passage of moisture carrying, through the flaws in the laying mortars and lateral rubbing, and bringing the clay to the surface of the expansion joints, especially on the left of the photo and in some places on the right.

The efflorescence is mainly demarcated in the blocks from its ends to the center, demonstrating that the settling mortar and lateral embedding is providing calcium and magnesium hydroxides, which are entering the capillaries of the blocks, exiting to the surface and, as a result, after carbonation, pure white calcium and magnesium carbonate salts are formed, since all the carbonates in group 2A of the periodic table form white salts.

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Here, we have a brickwork made of concrete block with a mortar rich in cement, painted with acrylic paint, whose moisture passes from the inside to the outside. The moisture passed, leached, and solubilized the calcium hydroxide and magnesium hydroxide, present inside the settlement mortar, which it donated to the blocks. This excess of calcium and magnesium hydroxide, with the increase in internal alkalinity, was able to make micro-holes in the paint, reaching the surface of the blocks, and when it came into contact with carbon dioxide in the air, through the reaction of “curing free lime”, salts and, consequently, efflorescence were formed, starting the degradation of the built environment.

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The example above shows efflorescence on a concrete block masonry plinth, which has a waterproofing flaw in the base. In addition, we can evidence a second pathology of efflorescence, with the salts crossing the acrylic paint and carbonating on its surface.

In view of the examples demonstrated about efflorescence in masonry made with concrete blocks, we must take into account that the presence of moisture coming from the inside out, in addition to causing aesthetic damage to the built environment, is also causing a more serious pathology, which is the degradation of the mortar and lateral rubbing as well as the degradation of the concrete blocks, with loss of mass in both cases.

In addition, in the coming years, we will see the manifestation of an increasing commitment to structures, since the hardware that is inside the concrete blocks, at the grouting points both vertically and in the horizontal channels, will undergo greater oxidation, increasing their volume since rust has a greater molecular weight than the iron contained in steel. Therefore, with greater molecular weight and greater volume, the hardware will expand, which will end up expanding the concrete mass and, finally, the expansion of the block walls will occur, leading to a degradation of the masonry.

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Efflorescence in Painting

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Here, we have the crushed mass moving away from the block and the mortar due to the presence of efflorescence. In this case, the runny mass received paint, which obviously also ended up coming out with the runny mass due to the efflorescence attack.

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In the photo above we can see the efflorescence causing the acrylic paint that is applied to a concrete block to displace.

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Efflorescence in Masonry

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In this image, it is possible to verify some effects that efflorescence caused in the masonry of ceramic brick. The problems identified in this photo are: the beginning of the loss of cement mass from the mortar vertically, the displacement of the mortar with the block, and a cohesive failure of the mortar.

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In this photo, we have a corner of a masonry wall, which was attacked by efflorescence, being expelled from the rest of the ceramic mass of the structural ceramic block. Thus, there was a loss of the block wall, which was caused by the pathology and that, if not treated as soon as possible, serious structural problems will arise.

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This photo makes quite evident the problem of the accumulation of water just above the slab, in its channel or in the first layer of settlement, with the considerably accelerated commitment of the surface layer of the block. There are approximately four blocks in which a thin blade has been completely eliminated from the block.

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Here, we have a completely flawed construction system, the notable of which is a lateral crackling mortar failure in the brickwork, which leads to reckless acoustic comfort. It is also possible to observe some examples of efflorescence, which appear on the brickwork and even on the chapisco. This proves that the efflorescence, in addition to leaving the laying mortar, passes into the block and even exceeds the chapisco layer applied on the masonry.

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Efflorescence in Ceramic Brick

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Many people say that ceramic blocks cause efflorescence, but this photo can prove that's not how it happens. In reality, efflorescence is mainly derived from calcium hydroxide and magnesium hydroxide, which come out from inside the settling mortar and side embed and migrate into the ceramic block, which is quite visible in the image. Therefore, the efflorescence will always come from the laying mortar, having nothing to do with the ceramic block. Some of them, depending on the type of ceramic, will have a more or less affinity for calcium hydroxide and magnesium hydroxide, which cause efflorescence in the settlement mortar.

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This photo, like the previous one, shows, quite clearly, that efflorescence is being generated in the settlement mortar and migrating to the ceramic block.

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Here, we can see an adhesive flaw in the laying mortar vertically, at the bottom with the ceramic block. We also found in the less calcined blocks that the internal presence of efflorescence in the block layers is already beginning to cause a “popping” on the surface. As an expansive matter, we have a small crack in the middle of the block starting and, finally, on the right, a deterioration of the mortar, which is gradually dissolving, which is visible by the lack of a piece of it.

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This photo is quite didactic. In the upper left corner, we found a less calcined spot of the block that has already been delaminated, spots more to the center-left with small spots on the surface layer of the block, which have a lighter shade, drawing to white, still under the upper clay layer of the block. And yet other points where the expansive force has already delaminated a surface part of the ceramic block. In other words, we can notice the beginning of the complete degradation of the ceramic block due to efflorescence.

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We see wear and tear on the mortar, because to have caused efflorescence on the blocks, the mortar had to lose mass. We also have the situation of the ceramic block, which was attacked by the efflorescence of the mortar, showing the almost complete delamination of the block and also a greater fragility in the layer subsequent to the surface of the block. Logically, after the efflorescence attack, due to the loss of mass of the settlement mortar and lateral rubbing, the mortars are more exposed to the attack of acid rain, so common in polluted cities, further deteriorating the construction.

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We have the very accelerated degradation of the structural ceramic block, caused by efflorescence, which has completely destroyed the first layer of the block, which consists of four layers, one of which has already been extinct by the pathology. Settling mortars also show fairly clear signs of wear, as they are falling apart and becoming porous. As it is a structural block, note that the efflorescence attacked the block so much that the structure of the building may be compromised.

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Here we have the completely degraded settlement mortar from the middle down, already consumed or eliminated from the surface of the lateral wedge of the blocks. It is a mortar failure that may have been eliminated by efflorescence, in addition to causing damage to the block wall, which is already beginning to delaminate in a very rapid manner.

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Efflorescence on the facade

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The image above shows a façade built with structural ceramic blocks, which have a higher incidence of efflorescence, making the blocks less resistant, and therefore more porous and subject to acid rain attacks.

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Here we have a façade heavily attacked by efflorescence, the mortars from the settlement and lateral rubbing have already lost a lot of mass and it is also possible to observe a ceramic block whose wall has already begun to detach from the rest of the masonry. In the future, very intense and serious structural damage will appear in this construction.

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Efflorescence in Coating

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Here, we see the built environment on the inner face of crushed PVA putty applied directly to the ceramic block masonry and a degradation process through the efflorescence of both the block and the lateral rubbing mortar. The efflorescence, after curing, forms calcium and magnesium carbonates, which are the white deposits visible in this photo and also, in this case, there is a reaction with the acidity of plaster. Therefore, we see a fairly thick layer of efflorescence, which is leading to a displacement of the runny mass applied as a coating.

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Here, we have a unique coating system industrialized with projected mortar, applied on a ceramic block surface, with a strong incidence of efflorescence. The complete displacement of the surface on which the coating mortar was applied is very visible.

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In this photo, we were able to observe the runny mass moving out of the brickwork, with efflorescence marks with fairly long crystals and a complete lack of substrate to anchor the runny mass after the occurrence of the pathology.

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With this photo, we were able to notice, in a single built environment, lack of labor training, lack of preparation, disrespect for good construction practices, and haste when delivering the work. Result: the lack of lateral mortar led the wall to a very high deformation modulus, as a result, microcracks and displacements appeared on top of a brickwork with clear signs of efflorescence, which were neither eliminated nor chemically treated. The very high deformation modulus leads to the appearance of microcracks, which facilitate the penetration of water, causing even more efflorescence in the masonry and, consequently, leading to large proportions of displacement in the work. It should be noted that this wall already showed serious signs of efflorescence during its execution process, which were not treated, further aggravating the situation.

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Efflorescence in Grout and Efflorescence in Floor

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This photo proves a construction system that was not well thought out, as there are several problems that could have been avoided. The construction system in which we are seeing is failing, as there is a waterproofing of the slab made with a blanket Asphaltic, followed by an adjustment mortar followed by the installation of the ceramic pieces. Firstly, the grouting system failed, because it was not a grout waterproof and totally flexible, in addition to not having followed the necessary expansion joints with the floor.

Thus, the water penetrates through a grout fault and ends up exiting through the most vulnerable points, where it is easier to escape. When it leaves, it washes away the free calcium and magnesium hydroxides from the cement, which will then carbonate, forming calcareous stains on the ceramic piece. In this case, they are temporary or permanent stains. Therefore, whenever the construction system is not well thought out, the consequences are drastic and inevitable.

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Efflorescence in a Pool

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Here, we have an example of a pool suffering the attack of efflorescence. We can see that this is the same case of efflorescence on the grout and floor, as I said earlier. Basically, water washes away calcium and magnesium hydroxides, which, when carbonated, form salts, which are deposited on the surface, creating the white spots that we see in the photo.

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Wall efflorescence

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In this photo, we see a ceramic block with its surface layers already quite degraded and a latent efflorescence, which caused the dislocation of the coating, of the crushed mass of PVA.

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The image shows efflorescence causing a delamination of the structural ceramic block. We can see that the wall is very aesthetically compromised, giving it an aged and poorly maintained appearance.

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Well, after everything I explained about efflorescence, I believe that the subject has been exhausted and that there are no doubts left, right?

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The consequences of not using the appropriate waterproofing agent and not taking care of the efflorescence as soon as it appears are very serious! Therefore, with the examples I separated, it was possible to see that it causes many problems and compromises, both aesthetic and structural, for buildings. Then, count on Blok for any challenge and discover our specific efflorescence products and have an excellent result in your work!