Do you know the common protective measures for Sichuan landscape stone?

2021-11-02 11:58

Wet pasting natural stone walls and floors during the construction process, the Sichuan landscape stone slabs will appear like "watermarks" patches. As the pasted mortar hardens and dries, the "watermarks" will shrink slightly, or even disappear, and become isolated and scattered. The land appears in the plates, but as time goes by, especially when the outdoor is repeatedly encountered with rain or wet weather, water invades from the joints of the slab or the surface of the stone, the water spots of the natural stone gradually become larger and connect into pieces in the joints of the slab. The plate is partially deepened, the gloss is dim, and white crystals are precipitated concurrently between the plate seams, which will not fade for many years, which seriously affects the appearance. This phenomenon is called efflorescence.


Two, analysis of the cause of returning alkali


1. Effusion caused by stone material:


①Natural stone has relatively coarse crystals, and there are many capillaries invisible to the naked eye. The granite has a pore rate of 0.5 to 1.5% and marble has a pore rate of 0.5 to 2.0%. Its impermeability is not as good as ordinary cement mortar and the water absorption rate of granite. 0.2~1.7% is low, and water can still be transmitted to the other side through the capillary immersion surface in the stone. This characteristic of natural stone and the existence of pores provide a channel for the penetration and precipitation of water, alkali, salt and other substances in the bonding material and the formation of efflorescence.


②The main component of stone is calcium carbonate, which accounts for more than 58%. When it is exposed to sulfur dioxide and moisture in the atmosphere, its surface chemically changes and transforms into gypsum, which quickly loses its luster and becomes loose and porous.


2. The bonding material causes efflorescence


① The bonding material produces substances containing alkali, salt and other ingredients. It is mainly used to paste the mortar to precipitate Ca(OH)2 (calcium hydroxide) and follow the excess mixing water to freely invade the plate along the pores of the stone. The more mixing water, the more Ca(OH)2 that moves to the surface of the mortar. After the water evaporates, Ca(OH)2 is stored in the plate.


②Additional additives containing sodium Na+ are added to the cement. The yellow sand used for paving contains Na+, Mg2+, K+, Ca2+, C1-, So42-, C032-, etc., which will dissolve in water and penetrate into the pores of the stone. , The formation of "white hua" and other phenomena.


③The alkali, salt and other constituent substances produced by the bonding material are the direct source of substances that penetrate into the pores of the stone to produce efflorescence.


Sichuan Landscape Stone


3. Water seepage causes efflorescence


Because the external wall joints are jointed with cement fine mortar, the waterproof effect is poor; ground water (or moisture) penetrates the stone slab along the wall or mortar layer; excessive water spraying on the stone during installation causes water to invade the stone slab. And dissolve Ca (OH) 2 and other salt substances into the capillary of the stone to form efflorescence. It can be seen that water is the solvent and carrier of efflorescence substances.


3. Preventive measures (control before and during the event)


1. Preparation before construction


①In the design, consider eliminating efflorescence, and design as dry hanging form as possible; consider the waterproof treatment of the structure; choose stone slabs with water absorption and other physical properties that meet the requirements.


②Before construction, we must fully consider the various construction process links that may occur efflorescence, and take preventive measures in advance. If you are not sure, make a model first.


③Relevant materials should be inspected before use. Not only the appearance and size are required to be qualified, but also the physical performance indicators are also qualified.


④Six-sided protection must be done before construction of all incoming materials.


2. Use anti-alkali back coating agent


①Before the stone slab is installed, apply a special treatment agent on the back and side of the stone. The solvent will penetrate into the stone and block the capillary, preventing water, Ca(OH)2, salt and other substances from entering, cutting off the path of efflorescence.


②Spread resin glue on the bottom of the stone slab, and then paste the chemical fiber mesh cloth to form a tensile and waterproof layer, but you must not forget to paint on the side.


3. Reduce the generation of Ca(OH), salt and other substances, and use special adhesives, such as mortar, etc., to reduce the Ca(OH)2 component of the bonding material.


4. Prevent water intrusion


① Do not spray large amounts of water on the stone and wall before operation, and wait for the stone to dry before paving.


②After the paving is completed, the outdoor stone can use a professional jointing agent to block the communication between the back of the stone and the outdoor air, and avoid the internal Ca (OH) 2 components from leaking out.


Sichuan Landscape Stone


5. Control and processing of materials


①Protect the interface of the stone, protect the back and sides of the stone, and apply the protective agent to make the applied protective agent penetrate into the surface of the stone to form a closed barrier to prevent the precipitation of moisture and alkali in the mortar. The specific method is: first clean up the five interfaces, and then apply the anti-seepage sealant twice. When painting, the surface should be dry and evenly painted. After painting, it should be dried in the shade, and then can be painted after drying in the shade. Brushing direction should be vertical once or twice.


②Surface protection For marble or outdoor matte granite, surface protection agent is used. Its function is to seal the gaps between stone structures, so as to achieve the purpose of waterproof, pollution prevention and erosion prevention. The construction method is the same as above.


③Control of cement related indicators: the content of sulfur trioxide must not exceed 3.5%, and the content of alkali must not exceed 0.6%.


4. Treatment measures for alkali reversion after the completion of construction (post-incident treatment)


Once efflorescence occurs in natural stone paving, the soluble alkali (or salt) substances have penetrated into the stone along the pores (the exuded slab surface can be removed), and it is difficult to remove it. Therefore, we should focus on prevention. The following remedies can be made.


1. Waterproof the surface of the board as soon as possible to prevent the intrusion of moisture and prevent the expansion of efflorescence.


2. Available stone efflorescence cleaning agents on the market can be used. The cleaning agent is a colorless and translucent liquid made of non-ionic surfactants and solvents. It has a certain effect on the cleaning of some natural stone surfaces. . But before use, be sure to make a sample test block to test the effect and decide whether to use it.


3. At present, there is a kind of back alkali that can be solved by using the back alkali scavenger SINO306. The method of use: a. Clean the back alkali part b. After it dries, apply the product one line c. Wait until the treatment agent is dry. Do one painting.