Effective ways to prevent cracks in external wall putty and anti-cracking mortar

In the application and practice of polymer plastering mortar and anti-cracking putty in exterior wall decoration and thermal insulation and energy-saving projects, many results have been achieved, and some issues are also faced. Discussed the technical issues related to the raw material system and application of crack putty, and put forward some new insights for the reference of the industry.
In the exterior wall decoration projects of urban public buildings and residential buildings in my country, because the exterior walls need to be insulated, it is necessary to combine the decoration projects with the thermal insulation and energy-saving projects.
The quality and technical level of exterior wall decoration projects mainly depends on the level of materials and craftsmanship. The author has done many years of research and experimentation, and conducted on-site inspections of some projects, and conducted extensive contacts with construction technicians. Through the technology of some engineering quality cases Analyzed and realized that the current main technical problem of external wall plastering mortar and external wall putty is anti-cracking, how can we solve this problem. We believe that we have to start with improving the performance and construction technology of exterior wall plastering mortar and exterior wall putty. This article starts from the theory and practical application, the material system of exterior wall plastering mortar and exterior wall putty, the relationship between the materials, and the cracks. The main reasons, the impact of cracks on the quality of building decoration projects and the effective ways to solve them are compared and comprehensively analyzed. The theory and practice are combined, and they are easy to understand for building materials manufacturing, building energy-saving engineering design and construction, and quality supervision. Reference for employees in related industries such as departments (production technicians, construction personnel, project supervisors, quality inspectors, etc.
1. Material system
Understanding the different properties of the material system and related raw materials is very helpful to improve the performance of polymer plaster mortar and exterior wall putty. The main raw materials currently used are inorganic cementitious materials: such as ordinary Portland cement, white cement, lime lime powder, calcium hydroxide, etc.; fillers: such as quartz sand, quartz powder, wollastonite powder, washed river sand, double fly powder , Heavy calcium powder, etc.; cellulose and fibers: such as methyl cellulose (MC), hydroxypropyl methyl cellulose (HPMC), wood fiber, polystyrene staple fiber, etc.; polymers: such as elastic emulsion, Synthetic emulsion, redispersible latex powder, polyvinyl alcohol powder, compound and composite additives, etc.; multifunctional rubber powder: polymer powder, etc., and other additives.
2. Economical and practical issues
The development and application of polymer plastering mortar, exterior wall putty products and their application technology to the national general promotion show that their economic and practicality are mainly in two major aspects. On the one hand, it is required to ensure that the product has excellent quality and stability, and Satisfying the various requirements on the quality of construction projects means having good practical application value. On the other hand, products must also have strong economic efficiency. At present, some new building materials are slowly being promoted in some areas, except for publicity. In addition to the lack of promotion, the main reason is that the product price is high and the project contractor is unwilling to buy it. The product performance and price status of polymer plastering mortar and exterior wall putty, from the overall situation and development trend analysis, with the intensified market competition, continuous technological progress and the development and promotion of new functional materials, the comprehensive performance of the product will be improved. With continuous improvement, the cost will be reduced, and it will be more widely used. In the production and application of polymer plastering mortar and exterior wall putty, we must also rely on technological progress, boldly adopt new materials, and continue to develop and innovate to meet the market demand.
3. The nature of raw materials and the relationship between each other

At present, many manufacturers have limited understanding of the functions and functions of various raw materials used in polymer plastering mortar and exterior wall putty and the relationship between them, and their practical experience is insufficient, resulting in unstable products and inability to exert good adhesion. Knot and crack resistance. Through long-term research, application and technical consulting services, it is very important for the author to fully understand and grasp the nature, function, function of the material and the relationship between the main and auxiliary materials. The key to the technology is to choose and use the raw materials.

First of all, cement products (PO or PW) as one of the main raw materials, the main role in polymer plastering mortar and exterior wall putty products is to play a bonding role, and its adhesion, weather resistance, moisture resistance and reliable stability Sexuality can be maintained for decades or hundreds of years. Cement is an inorganic cementing material. It is characterized by a hydraulic material. The hydration and setting hardening of cement is a continuous process. The first hydration and then the setting. The result of the setting and hardening depends on the hydration conditions. The more fully hydrated. The better the water curing, the better the corresponding strength and stability; the hydration and hardening speed of cement is also obviously affected by the ambient temperature, that is, the higher the ambient temperature, the faster the hydration and hardening speed, and the lower the ambient temperature , The speed of cement hydration and setting and hardening is correspondingly slower. Cement will inevitably produce strong drying shrinkage during the setting and hardening process. This dry shrinkage will cause stress inside the mortar, which will damage the structure and cause cracks. This is commonly referred to as cracking, hollowing, shedding, and cement shrinking. The occurrence of cracks is a universal problem.

As the most important raw material, polymer products mainly help cement to fully hydrate, increase viscosity, retain water and resist cracking. It improves the bonding strength of polymer plaster mortar and exterior wall putty, stabilizes performance, and prevents cracking and cracking. , It plays a great role in many aspects, such as improving the construction performance. The filler acts as an aggregate reinforcement in the polymer plastering mortar and exterior wall putty. It can work with cement to produce a better mechanical structure, which is effective in bonding strength, compressive strength, flexural strength, and structural strength and tensile strength. Anti-cracking, etc. have a certain effect, so it is also very important to choose what kind of aggregate and what size aggregate.

Four, application practice

Polymer plastering mortar and exterior wall putty have been popularized and applied for many years. Because ordinary mortar plastering surfaces are often prone to cracks, hollowing, and falling off. In order to solve this technical problem, the exterior wall plastering mortar or exterior wall in Beijing in the earlier period The putty is mixed with construction glue (such as polyvinyl formal adhesive, and later construction emulsion, elastic emulsion, synthetic emulsion, etc.). The purpose is to increase the bonding strength and flexibility of the cement slurry and prevent cracking and shedding. But after more than ten years of practical application verification, these methods are difficult to solve the problem. In recent years, the use of methyl cellulose ether (MC), or hydroxyethyl cellulose (HEC), hydroxypropyl methyl cellulose (HPMC), polyvinyl alcohol powder (1788, 2488, etc.), redispersible latex Dry-mixed mortar, exterior wall putty, etc. produced by powder, lignocellulose, etc., have achieved some results, but they are limited. Because the above-mentioned products have a single function and are not well-targeted, they are effective in the hydration, coagulation, natural curing, and later stage of cement. The effects of strength stability and prevention of cement shrinkage cracks are not ideal, and the product cost is relatively high. Some new functional products, such as the redispersible latex powder product produced by Gomez Chemical’s polymer polymer, are very good. The polymer bonding mortar, plastering mortar and exterior wall anti-cracking putty produced by this series of rubber powder Expansion polystyrene board thin plaster external wall external insulation system, thermal insulation slurry, architectural coating projects (including external wall cracking putty, fluorocarbon paint primer, fireproof coating, etc.) have many years of successful application experience, and the effect is good , Can meet the requirements of project quality.

Five, the main reason for light cracks

Analysis of the main causes of cracks The author has analyzed from years of experience in engineering and technical consulting services, there are many reasons for cracks and cracks in polymer plastering mortar and exterior wall putty. The most important thing is the cracks, hollowing, and shedding caused by the internal stress generated during the drying shrinkage of the cement; the second is the occurrence of cracks and cracks caused by the subsidence of the foundation and slight earthquakes. In the product, the raw materials used in the model, specifications, quality are not up to the requirements and improper proportioning will also lead to poor product bonding performance, prone to cracks, cracks, or even hollowing or falling off; there are obvious cracks, cracks or cracks in the base of the wall. The grass roots have pulverization, looseness, oil stains, etc., which can also cause cracks, hollowing, and shedding. Under normal circumstances, regardless of the horizontal and vertical, as long as it is a straight crack or a crack, it should be caused by the stress caused by the subsidence of the foundation and the change of the wall structure. If there is a large area of ​​obvious cracks, it should be mainly due to the poor crack resistance of the base layer, construction, and the product itself.



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