Common knowledge of coating: analysis and Discussion on the causes of cracks in the coating layer of building exterior wall

Abstract: Based on the analysis and discussion of the causes of the cracking of the exterior wall coating of a large residential quarter project in Hangzhou, this paper introduces the control methods and prevention measures to eliminate this quality defect for discussion Key words: exterior wall coating; cracking reason; analysis and discussion Chinese Library Classification No.: tu712 document identification code: B Article No.: 1007-4104 (2014) 02-0064-02 1 General situation of project construction There are 14 small high-rise and high-rise residential buildings in a large residential area project in Hangzhou, with a total building area of 1 Which is the price of Dajin diatom mud Recommended brief introduction: which is the price of Dajin diatom mud? How to buy genuine diatom mud? Guangdong diatom mud agent suggests placing a basin of cold water in the air conditioning room, so that the diatom mud wall can breathe effectively The feature of the breathing wall is obvious When the indoor air is dry, the diatom mud wall will release the absorbed water quickly Put it out to help regulate the indoor dry humidity It is suggested to place a basin of cold water in the air conditioning room, so that the wall of diatom mud can breathe effectively The feature of the wall that can breathe is obvious When the indoor air is relatively dry, the wall of diatom mud will absorb the water Abstract: Based on the analysis and discussion of the causes of the cracking of the exterior wall coating of a large residential quarter project in Hangzhou, this paper introduces the control methods and prevention measures to eliminate this quality defect for discussion Key words: exterior wall coating; causes of cracking; analysis and discussion of classification No in Chinese drawing: tu712 document identification code: B Article No.: 1007-4104 (2014) 02-0064-02 1 General situation of project construction: a large residential community project in Hangzhou has 14 small high-rise and high-rise residential buildings, with a total building area of 170000 m2, frame shear structure residence, basement 1 floor, divided into three construction sections of a.b.c Among them, section a was started on August 8, 2010, and is expected to be completed by the end of December 2013 The other two sections are also started and completed successively during this period 2 General situation of external wall painting and coating construction the main structure works of bid a were all capped at the end of October 2011, and in the first ten days of November, the external wall painting construction was fully carried out As the number of 11 floors is the highest (28 floors), the construction company mainly arranged the internal and external wall painting team in 11 floors, from top to bottom Before entering the large-area painting construction, the construction project department, under the strong demand of the site supervision, first makes the painting sample room in the basement Through the experiment, the construction team was replaced, which made the painting progress slow at the beginning under the strict quality standards and requirements of the sample room 11 When the building is plastered from top to bottom to the 25th floor, when the mortar strength of the external wall is not up to the expected strength, the construction team for coating of the external wall has entered the site for construction, closely following the external wall for coating, and the up and down parallel cross operation As a result, under the strong demand of the site supervision, the painting team was forced to stop work and was expelled to bid B and bid C for exterior wall coating construction 3 Until now, the quality defects were found on the 25th floor of 11 × building in a standard The painting layer of air-conditioning partition had partial cracks (not found on the wall), and then the coating layer also had cracks The cracks were uneven in size and spacing, and the surface cracks were serious No large area cracks were found in 9 × building and 10 × building However, the cracks of B and C exterior wall coatings are serious with the painting layer, with large area, deep crack, many layers and even peeling off 4 Cause analysis and discussion (1) wall cracking is the most direct and main cause of paint layer cracking Wall damage, cracking and water seepage affect the safe use; foundation sinking, foundation subsidence, poor support, too dry demoulding, quality defects of concrete materials and construction quality of external wall are all the direct causes of external wall cracking External wall cracking is the biggest potential safety quality hazard of the main body of frame shear structure, which must be resolutely eradicated in construction (2) The surface flatness of the exterior wall is poor, the thickness of the painting layer is uneven, and the partition board of the air conditioner is thin, which can also cause different degrees of cracking of the painting layer (3) The defects of the material quality and construction quality of the mortar are the main reasons for the cracks of the painting layer Cement soundness is unqualified, strength is low; sand fineness modulus is unqualified, mud content is large; waterproof Unqualified agent performance and poor waterproof effect can cause unqualified mortar quality; improper construction ratio, high cement content, uneven mixing, too long use time, low consistency, poor bleeding, high construction temperature and inadequate maintenance make the surface more prone to crack or even crack (4) Sealing material and construction quality are also crucial What kind of material is used to make the sealing layer, whether it can seal the cracks in the base layer, has a certain impact on whether the coating layer cracks, peels and falls off If the high-quality primer is used as the sealing layer, it is not easy to age and crack, it can effectively seal the cracks in the base layer, prevent the cracks from penetrating, form reflection cracks, and protect the coating layer from cracking (5) The process arrangement and interval of painting construction, sealing treatment and coating application are the main factors that restrict the crack of painting layer Because after the main body is capped, the construction party is eager to do the painting construction from top to bottom in order to rush for the progress At this time, when the concrete age of the exterior wall is less than and the water content of the exterior wall is not enough to evaporate, it will be covered with a thick outer package and sealed In this way, during the early strength formation period, the heat dissipation of the concrete itself is large, and in addition, the maintenance of the concrete itself is not in place, the wall will crack and the surface will crack in high temperature season, which will have a squeezing expansion effect on the paint layer, and the paint structure will crack, without giving the exterior wall structure a A reasonable pre cracking period, forming pre cracking after construction, forming shooting cracks in the painting structure layer If the painting is done and then the sealing layer is painted, the painting layer also has no pre cracking period and pre cracking after construction, and the possibility of surface cracking is greater The external wall painting of bid section a starts from top to bottom, because the number of 11 floors is the highest (28 floors) The construction party arranges this way to balance the overall progress The painting is done below and the coating is done above Not only the process interval is unreasonable, the process arrangement is improper, but also the up and down parallel operation, which has a great potential safety hazard Therefore, our on-site supervision department issued a notice to the supervision engineer, requesting that the coating construction be stopped, and that the painting be done one month after the construction of the outer wall As a result, the painting construction team was sent to bid section B and C for construction, so that bid a was finally painted So up to now, we only found that the paint on the painting layer of the air conditioning partition above the 25th floor of the 11th floor of the a standard cracked partially, which led to the pull crack of the paint No other floor has been found (6) The waterproof performance and strength of exterior wall plastering mortar are greatly affected by the temperature, humidity and frost heave of the external environment After cold winter, the surface cracking may be more serious, and even in hot summer, large area peeling and falling off may occur (7) The quality of coating itself is more important The exterior wall coating design of the project should be high-grade elastic coating, but in the owner's bidding document and the construction party's bidding document, we can't find the word "elastic" Results the construction company used a kind of non elastic flat coating If the "elastic" coating was used, its crack resistance would be very good, which would not lead to large-area crack 5 Treatment methods and prevention measures (1) strengthen the quality control of external wall formwork, support, reinforcement binding and concrete pouring, ensure the construction quality of the external wall of the building, and prevent the cracking of the painting layer due to the cracking of the external wall (2) Strictly control the quality of formwork erection of exterior wall to ensure the flatness of wall surface (3) Strictly control the quality of mortar materials and construction quality to prevent cracks on the surface of painting layer caused by unqualified cement materials (4) Select the qualified sealing primer materials, and do a good job in sealing (5) Reasonably arrange the time interval of external wall concrete pouring, curing, painting, sealing and coating construction process (6) Select qualified waterproof admixture, and try to avoid the season construction with large temperature difference (7) The high-grade elastic waterproof coating is selected for exterior wall painting, and the unqualified coating is not allowed to be used for painting works 6 epilogue According to the cracking situation of exterior wall coating along with the painting layer in the project, in the hot summer, strictly control the time interval of each procedure of exterior wall concrete construction, painting and painting, and give the wall concrete and painting mortar a reasonable pre cracking period after construction, which is the key to eliminate the reflection cracks between layers and cure the cracking of exterior wall painting layer; if the high-grade elastic coating is used for exterior wall painting, its anti cracking property is The cracking performance will be increased, but if the degree of cracking or surface cracking is too large, it will also crack In view of the local cracking of the exterior wall coating along with the painting layer of the project, it is recommended to use high-grade elastic coating Under the condition of ensuring safety, repainting will be carried out Of course, if it is not handled, it will not affect the safe use of the paint The home is focused on coating, diatom mud, paint coating, coating technology, news information and coating of fireproof coating, diatom mud, paint coating, coating technology, decoration knowledge and decoration effect map of fireproof coating,