"Approaching Meihui" Vol. 6 | How to solve the problem of efflorescence, cracking of exterior wall coatings, and hollowing phenomenon appearing on the wall after applying the roller interface agent?
Release time:
2021-10-02
Source:
Q1 Why does the exterior wall coating show efflorescence?
Analysis:
1. The substrate is too alkaline, and the coating is applied without removing the alkalinity.
2. Cracks or water seepage appear in the wall, causing moisture to enter the putty layer and substrate. The moisture brings alkaline substances from the wall to the coating, forming a layer of white substance on the surface. At the same time, due to its high alkalinity, it corrodes the coating layer, leading to discoloration, fading, and peeling of the coating.
Solution:
1. Implement necessary waterproof measures, especially for roof gutters and parapets.
1. Eliminate substrate alkalinity: Mainly for the mortar plaster layer, water curing should be done (3-4 times) to ensure the cement fully polymerizes, which will quickly reduce its alkalinity.
● If watering conditions are not available, relying on natural rainwater and natural polymerization will prolong the drying time, requiring at least 20 days (possibly more than 30 days in winter). Therefore, watering the mortar plaster layer is the best method to reduce alkalinity.
● Qualified cement is the foundation for eliminating substrate alkalinity.
2. Eliminate putty layer alkalinity: The key to eliminating putty layer alkalinity is to choose high-quality putty. This type of putty has good hardness, is water-resistant, and has low alkalinity (pH value less than 10).
At the same time, after the putty is applied, it should be watered 1-2 times promptly to ensure the cement in the putty layer can fully polymerize and harden, thus lowering the pH value.
3. Use a good sealing agent to penetrate and seal the substrate and putty layer, making it difficult for alkaline substances to penetrate into the coating with moisture. This is a symptomatic treatment method. However, if the sealing performance is not good enough or if there are too many alkaline substances in the substrate putty (pH > 10), efflorescence will still occur.
Q2 Why did the Meihui Stone-like paint exterior wall crack?
Analysis:
Many people believe that exterior wall cracking is a problem with the coating application. In fact, it is due to the failure to address wall cracking in a timely manner, leading to a series of subsequent problems.
Regarding exterior wall decoration, the causes of cracks include cracks caused by differential settlement of the building, thermal stress cracks, and shrinkage cracks.
1. Cracks caused by differential settlement of the building:Uneven settlement of the building can cause additional stress within the structure, and the significant differences in the linear expansion coefficients of various materials can lead to the occurrence of cracks.
2. Thermal stress:When there is a large temperature difference, different materials will expand and contract differently due to their varying thermal expansion coefficients, leading to the possibility of thermal stress cracks.
3. Shrinkage cracks:Except for clay bricks, wall materials have a much larger shrinkage rate after drying compared to brick walls. Shrinkage can generate significant stress, and when this stress is strong, combined with insufficient strength of the cement mortar, poor adhesion, or incomplete mortar joints in certain areas, cracks will appear on the wall surface. These cracks are generally quite small.
Solution:
1. Segmented buffering: By segmenting the wall into relatively independent units, the joints in between are treated with special putty to isolate the blocks from each other, thus achieving the effect of segmented buffering.
2. Control of civil construction:During civil construction, control over plaster thickness, cement mortar ratio, and sand particle size is crucial, especially for non-clay brick construction processes, such as fly ash bricks and aerated bricks. Waterproofing before and after construction, and strictly controlling the width of mortar joints between 8-12mm, with a saturation of 100% for mortar joints, should be enforced to eliminate the possibility of cracks.
3. Buffering with crack-resistant mortar layer:Inter-layer buffering is a very important step. Even if the strength of the cracks meets the standards through crack-resistant mortar and fiberglass mesh control, it can still be effectively blocked by inter-layer buffering, preventing cracks from affecting the surface layer.
4. Process control:Control the thickness of the putty during construction to completely eliminate the source of cracks.
Q3 Why does the wall still show hollow spots after rolling on the interface agent during the renovation of the old Stone-like paint?
Analysis:
The appearance of hollow spots on the wall after rolling on the interface agent may be caused by the following reasons:
1. The old substrate was treated with oil-based paint and not sanded;
2. The substrate is not solid or clean enough;
3. Improper application of the interface agent;
Solution:
1. Sand the oil-based paint substrate.
2. Solutions for insufficiently solid and clean substrates:
Check for hollow spots, water seepage, and cracking issues:
a. Remove hollow spots and fill with cement mortar;
b. For cracked areas, tap 10cm wide on both sides until reaching the brick wall layer, and add iron mesh for plastering. (Except for structural cracks)
c. For water seepage areas, treatment should be done from the inner wall, mainly in areas like bathrooms, balconies, and parapets.
3. How to apply the interface agent:
Clean the substrate before application.
a. For tile renovation putty (powder + emulsion), mix thoroughly and apply a coat;
b. Roll on two coats of the interface agent evenly.
Note: The interface must be fully dry.
Common issues with exterior walls.
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TEL /400-995-8827
Address: Quanhui Petrochemical Park, Fujian Province
Website: www.fjhuixing.cn
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