9 Problèmes et solutions concernant le mastic pour murs extérieurs dans les projets de peinture

With the improvement of people’s requirements for the quality of building decoration and the continuous introduction of coating products, various problems of exterior wall putty in the coating process have attracted increasing attention. This article summarizes 9 major issues and solutions prone to exterior wall putty in construction, hoping to provide application experience for related industries.

Problem 1: The putty strength is weak when applied on a dry surface or in a dry environment

Most of the exterior wall putty is hydraulic materials, and the strength of putty will continue to increase under the condition of moisture. If the exterior wall putty is too dry, the putty lacks moisture, which causes the hydration reaction to stop. When the hydration is incomplete, the performance strength of putty is low, and there may even be serious chalking. In this case, water can be adequately sprayed on the wall before construction, or after the putty is scraped and polished, the water can be strengthened to maintain the putty so that the putty that has stopped hydration can continue to hydrate to increase its strength.

Problem 2: The stirred slurry will harden when stored to the next day

Hydraulic putty has a set time limit. At an ambient temperature of 20°C, the putty will generally reach the initial setting for about five hours in the bucket. It will become challenging to scrape the putty after the initial setting.

Properly control the scraping time to avoid hard putty caused by prolonged storage.

Problem 3: Construction in a high-temperature environment will accelerate the hardening speed of the putty

At high temperatures, the hydration speed of the cement in the exterior wall putty will increase, which will cause the putty to shorten the setting time, and the putty will take longer to harden when it is stirred and placed in the container. Try to reduce the amount of putty mixed each time, and combine the functional ability of the workers, so that the mixed putty can be scraped before the exterior wall putty hardens. Especially when repairing lines, because the amount of putty used is small, the construction time of workers is long, and the amount of putty mixed is less.

Problem 4: The construction of cement paste wall is prone to shelling and peeling

The putty has a high probability of shelling and peeling on the cement paste surface that has just been constructed because the cement paste surface that has newly been constructed is very alkaline. When the dampness is high, the surface of the pure paste will form very loosely structured CaCO₃ crystals. At this time, after the putty is scraped on the wall, the adhesion with the base layer is very weak, and the phenomenon of shelling and peeling in the later period is inevitable.

Try not to apply putty on the cement paste surface because there is a high probability of problems. If construction is required, you must wait for the essential elimination of alkali on the pure pulp surface (more than one month), then wash the wall with dilute hydrochloric acid or dilute oxalic acid to remove most of the calcium carbonate crystals and wait for the wall to dry before proceeding with putty construction.

Problem 5: Special attention should be paid to construction during the rainy season

During construction in the rainy season, the exterior wall putty is soaked by rain before it is dry (usually within 1 to 2 hours) after installed on the wall. Because the putty is not dried to form a film, it cannot produce sufficient structural strength, so it cannot resist rain soaking at all. The soaked putty layer will peel, and the internal structure will be loose. If the paint is applied after drying and sanding, the paint layer will also peel off after several dry and wet cycles.

It is necessary to monitor the weather conditions strictly and arrange the construction time reasonably. If the exterior wall putty is soaked by rainwater, it must comprehensively inspect and thoroughly remove the loose parts soaked and then perform the partial putty repair.

Problem 6: In a damp wall or a wet construction environment, the putty will have excessive early strength

Under the condition of sufficient water, the cement components in the cement-based putty are fully hydrated, and the hardness is very high, which will cause difficulties for later workers to polish.

Try to apply putty in a drier wall environment. The early hardness of putty will not be too high in the state of lack of water, and it will be easier for workers to polish. After the polishing work is completed, the putty will continue to increase in strength by spraying with water and curing and finally meeting the subsequent coating process requirements.

Problem 7: There will be a small bubble problem in the construction of the base surface with damp steam

Some exterior walls putty seem to be dry on the surface, but the internal moisture is very heavy. When the humidity inside the wall is greater than the humidity of the air outside the wall, there will be a pressure difference, and the moisture will diffuse to the outside of the wall. If the exterior wall putty is scraped on the wall at this time, because the exterior wall putty has a large viscosity, dense tiny bubbles will appear immediately.

In this case, you can perform thin batching and compaction for the first time to block the steam holes on the wall and then scrape the second batch immediately before the first pass is dry, which can significantly reduce the number of tiny bubbles.

Problem 8: Pay attention to the problem of cracks on the base surface

When cracks appear on the base surface, the putty layer (if R-type exterior wall putty can resist cracks below 0.6mm) will also be cracked when the crack exceeds 0.3mm. According to the frequency of thermal expansion and contraction of the base layer cracks and the frequency of wet expansion and dry shrinkage, the time when the exterior wall putty is stretched and cracked will be different.

Before construction, carefully check the cracks of the mortar layer (the hardening shrinkage cracks of the mortar layer will appear after about one month, try to wait for the exterior wall putty construction after one month of the mortar layer construction), and choose different types of putty formula and coatings reasonably. It is recommended to use exterior wall putty for walls with more cracks in mortar turtles (the width of mortar cracks is allowed to be less than 0.6mm).

Problem 9: The hardness of putty

The surface hardness of putty is an issue of general concern. Some people in the industry or outside the industry regard the hardness of putty as the standard for judging the quality of putty, which is a comparatively apparent and one-sided j udgment basis.

Surface hardness is not the standard for judging the quality of putty, and putty must have comprehensive performance (under the industry-standard JG/T157-2004 “Putty for Building Exterior Walls” no index of the putty compressive strength in the industry standard. The hardness of the putty is moderate (5Mpa for 28-day compressive strength is appropriate). When the hardness is too high, it is difficult for workers to polish in the early stage, and it will cause fine cracks in the paint finish layer in the later stage.

The engineering quality problems of interior and exterior wall putty of buildings are diverse. In the construction of the project, it is necessary to scientifically grasp the physical and chemical properties and construction rules of the putty under the premise that the putty products on the site are strictly controlled to meet the various indicators stipulated by the industry standard, to prevent the occurrence of related quality accidents. if you have other questions,please contactez-nous.