As a kind of high-grade decorative material, stone is loved by everyone. But the more you love, the more you will be troubled by some of its flaws.
“Return to alkali (alkali)” is one of the most talked about in stone caregivers, and it has also become one of the most concerned issues. Standing on the cusp of the cusp, let us come to the popular science and other "back to alkali (alkali)" what is it?
This article originated from the landscape state
One: Why does the stone return alkali?
Return to alkali and moisture symbiotic, stone returned to the three basic factors: the porous nature of water, cement, stone.
The three elements of returning alkali
The return of alkali to stone, these alkaline substances do not come from the stone itself, but from the cement behind the stone. Therefore, the majority of return alkali problems occur on the surface of stone that is cement bonded. The use of adhesives, or dry hanging, etc. installed stone, return alkali is rarely possible.
The composition of cement is complex, but sodium hydroxide, calcium hydroxide, etc., are the main substances that form back-alkali.
2 Porous porosity
The material characteristics of natural stone are densely covered with nanometer and micron micropores and microcracks. These structures are channels for basic materials, water, etc., into and out of the stone.
3 water, moist
Water, which appears as a solvent, is the most important “pushing hand” that causes return-alkaline problems. It can also be said to be the “culprit.”
Return alkali in humid environment
II: The process of returning alkali
The stone used for the bonding material using cement as a bonding material, under the premise of long-term contact with water and moisture, alkaline substances such as sodium hydroxide and calcium hydroxide in the cement are dissolved in water, and along the micropores and micro-stones throughout the stone. The fissure structure, driven by the capillary action and the transpiration of water, is carried to the surface of the stone and precipitated. When these alkaline substances precipitate out of the stone surface. Two changes will occur over time:
1 change 1: condensation
After the water brings the alkaline substance to the stone surface, it quickly evaporates. Alkaline substances will condense and precipitate on the surface of the stone, forming a powdery substance.
This is the initial stage of the entire return alkali process. The return alkali at this stage is easy to wash away.
2 change two: deterioration and curing
Sodium hydroxide and calcium hydroxide are active and strong alkaline substances. It is very easy to chemically react with carbon dioxide and sulfides in the air to produce new compounds such as calcium carbonate and sulfides. And it gradually solidifies and becomes hard to clean. Therefore, the subsequent generation of the substance is not the same as the nature of the return alkali in the primary stage. Therefore, we call it "Baihua."
III: Analysis of Causes of Common Landscape Efficient Alkaline Problems
(1) The inner side of the landscape wall is not waterproof, and rainwater flows from the ash seam to the front of the landscape wall to form effluent pollution.
(2) The construction of swimming pool pressure top does not meet the requirements, resulting in pan-alkali phenomenon.
(3) The planting soil is higher than the bottom line of the pressured rock. The construction is not standardized, and panto-alkali phenomenon is easy to occur.
(4) Waterscape stone finish basalt.
Four: stone back to alkali, prevention is greater than governance
1, before the stone installation, full and effective protection, curb the return of alkali stone (alkaline)
1 According to the type and material characteristics of the stone, the stone protection is effectively selected, and the limestone metamorphic rock selection protection agent needs to have anti-alkali function.
2 wet stone bottom and surface separation, protective agent used in stone base must not only prevent alkali and salt, but also does not affect the adhesion (such as: BS H2O, A-16S, etc.), not because there has been "water-proof adhesive" And the stone bottom protection is omitted, and the limestone surface should be waterproof and anti-alkali (such as SOL170);
3 For carbonate stone materials, especially relatively soft marble, avoid the use of methyl sodium silicate as a strong alkaline protective agent (ordinary water-soluble protective agent); be sure to use a mildly alkaline, environment-friendly, high-end water-soluble protective agent. Correctly remove the alkali mist on the residual stone surface;
4 Before the protection, ensure that the stone is completely clean and dry, do not leave water in the stone. If this condition is not met, it is better not to be protective, and not to be barbaric.
5 The implementation of protection must be evenly saturated, and the different dosages should be determined due to the different water absorption rates of the stone;
6 After the protection, ensure the scientific overhead health, avoid drying and grab time.
Granite veneer panthelin phenomenon
2, "a" against "three" blocking
1.1 Prevention of return alkali, protection must be done. The problem of protection, we have already spoken many times, does not need to be repeated here. Mainly to remind two points:
1 Do not use a moisture-proof agent such as sodium methyl silicate as a stone protection agent. This moisture-proof agent not only has poor durability, but it also hydrolyzes alkaline components, and it itself becomes the cause of return alkali. Stones still need to choose professional protective agents containing silicone and silicone components.
2 Brush protection It is meaningless to discuss "doing nothing". Insufficient usage, or random brushing, uneven brushing, and doing no amount of work. Brush protective agent must be "full coverage, no dead ends, the amount of enough."
Protection is also a "plugging" technology, which blocks the main surface of the stone and micro fissures and micropores on the sides.
1.2 Three "blocking"
1 Blocking from the back: The stone adhesive is very important. If you do it well, you can seal it on the back of the stone and separate the bottom alkaline material into the stone channel.
2 Blocking during grinding: Some stones can be scraped and then ground, blocking the micro-cracks. When grinding, special grinding plates can be used to close the micro-holes on the surface of the stone. Block water and pollutants.
3 Blocking during polishing: Try to avoid using acidic polishing materials to weaken the protective effect and change the surface structure of the stone. Physical coverage with glazing technology can better close the surface micropores.
3, stone repair problem
Even if it is protected, there are a lot of cracks and cracks in the stone. The passage of these moisture and pollutants into and out of the pipeline can not be blocked with the protective agent, and it must be repaired by the glue. Large cracks are well handled. But how do you fill in the tiny cracks that are so small that you can see and see?
Our suggestion is that for some special plates, after the overall squeegee, the special grinding plate is used for grinding.
Squeegee has the effect of filling micro cracks. Filling itself is a kind of "blocking." And special grinding pieces, such as VD easy grinding pieces, can also fill the effect of the resin, blocking the pores of the stone surface, to block the role of water and pollutants.
Nowadays people know more about protective technologies, but the role of glue and grinding tablets has been largely ignored. This link, in fact, is very important. However, in practical projects, few owners are willing to understand such technologies and costs. Few construction teams also have such skills.
Severe back caustic (granite efflorescence)
4, polishing technology is very important
No matter whether it is powder, agent or paste, it contains acidic components, and the effect of light is achieved by chemical etching. However, acidic components on the one hand will damage the protective effect; on the other hand, it will also damage the surface structure of the stone and enlarge the pores of the stone. For marble that is maintained for a long time with powder or agent, there will be chicken paw patterns. This is the reason. The superposition of these two causes will create conditions for the water to enter the stone. With the participation of water, the chance of returning to alkali is even higher.
Therefore, it is better to use the sealing technique when polishing, and use the silica component to directly cover a hard and dense protective layer on the surface of the stone. More completely plugs the microscopic pores of the stone surface, preventing moisture and contaminants from entering and leaving the stone. Without water, it is impossible to return alkali.
This is why some of the stone returned to the alkali, we directly recommend the customer to use the sealed glaze material thrown 4 to 5 times, without protection can also be back to alkali causes.
Back to alkali in the pool (pan-alkali phenomenon of mosaic veneer)
Install stone and try its best to mount it. For grounds that cannot be mounted, reduce the amount of water as much as possible. If necessary, use a bead of cement as a paving base to effectively reduce and prevent the alkaline substances in the cement from evaporating upward with moisture.
Dry hanging technology
Five: Stone has returned to alkali, how to control?
1, the choice of protective agent
Washing or preventing the return of alkali and brushing the protective agent are all necessary and crucial steps. The choice of protective agent, in addition to the well-known oily protective agent, water-based protective agent. In fact, there is a better type of protective agent, that is, an organic fluorine protective agent. In terms of effect:
Organic Fluoride Protectors> Oil Protectants> Water Protectants
This is because the main component of the common oil-based protective agent is silicone, but the organic fluorine-protecting agent is added with fluorine to form a stronger molecular chain, and the protective effect and durability are better. Of course, the disadvantage of the organic fluorine protective agent is its high cost, which has not yet been widely used in China. But owners who have the ability to accept, may wish to try this excellent protective effect.
2, governance methods
2.1 Prevention during renovation
Step one: grind to 150#, dry for more than 24 hours to dry the stone completely.
Step 2: Use high-quality oil protection agent or organic fluorine protection agent, pour it on the ground and spread it with a scraper to a sufficient amount and uniformity.
Step 3: Keep the surface clean for more than 24 hours.
Step 4: Use crystal facer + pad, finely grind to 3000#.
Note: If there is a higher requirement for protection, water-based protective agent can be added to the grinding water during the grinding process to perform basic protection. But in the end this oily protection is essential.
Comments: The key to this method is to dry the stone completely. In addition, good protection can be waterproof and anti-fouling, and sealing technology can also fill the micro-fissures on the surface of the stone to prevent moisture and pollution.
2.2 Polished back to alkali treatment
If it is a return alkali formed after polishing, and is not ready to be refurbished, the following methods can be taken:
Step 1: Use a scrubber, or a crystal noodle machine + a scouring pad, with a stone soap solution, or with a SINO stone cleaner for overall surface cleaning.
Step 2: Drain the water slurry. Allow 24 to 48 hours to dry the stone thoroughly.
Step 3: Pour the penetrant type protective agent or the organic fluorine protective agent on the ground, throw it on the crystal facer + pad evenly, and absorb and dry the protective agent. Do 2~3 times.
Step 4: Keep your health for more than 24 hours. Clean the surface.
Step 5: Use crystal facer + pad to do sealing treatment.
Comments: Even if there is no return to alkali, this method can also be used for early prevention. Deep cleaning removes alkali components. And through the protective agent polishing, infiltrated into the surface of the stone, with the sealing glazing technology, can play a role in blocking moisture and preventing alkali return.