Ways to avoid cracks and cracks in exterior putties

Polymer dry-mixed surface mortar, exterior putty in the construction of the external wall decoration is of great importance. The external wall putty cracking problem is a lot of real estate developers, construction companies, decoration personnel, property management and maintenance personnel, building materials production The biggest headache for manufacturers. The causes of cracking in the outer walls are complex and must be mastered in the performance of relevant materials, construction techniques, mutual relations between materials and technical principles, scientific selection and use of materials in order to ensure product quality and construction quality.

Conch Cement     Fuhuai Stone

First, the advantages of dry-mixed polymer mortar, wall putty

Dry-mixed polymer mortar and exterior putty are widely used in exterior wall decoration and decoration projects. They have the following advantages:

1, good quality. They use factory specialization and standardized production with stable and reliable quality. Avoid blindly self-purchased materials on the construction site, and the construction personnel randomly deploy and have quality problems.

2, quick construction. It can be used by adding water and stirring. The product has good workability, strong water retention, no sagging, easy adhesion, can improve work efficiency, and reduce the labor intensity of construction workers.

3, high bond strength. Due to the full effect of the polymer in the product, it can promote the cement to be fully hydrated, improve the cement mortar's ability to fully utilize the natural conditions to realize self-maintenance, increase the late strength and stability of the cement, and control and prevent cracks and voids caused by shrinkage. Drum and shedding phenomenon.

4, green. The product does not contain volatile harmful substances and is harmless to the environment and human body. It is a green ecological building material product.

Second, the main cause of crack cracks in plastering plaster and wall putty

Cracking and cracking of cement-based mortar and putty are a common problem. After years of research and practice, people in the industry believe that the causes of cracks and cracks in the plaster, wall putty mainly come from the "internal cause" and "external cause".

1, "internal factors"

The "internal cause" is mainly due to the dry shrinkage of some trowel mortars and putty products, which are caused by dry shrinkage, resulting in greater internal stress and damaging the structure of the mortar. The performance of the cracks is generally irregular and cracking. Frequently said cracks. Turtle cracking is mainly due to the fact that some manufacturers do not fully understand the nature, function and technical principles of raw materials, raw materials used do not meet the requirements, and the formula is unscientific, resulting in unstable product quality, poor crack resistance, and large area cracks soon after construction. , hollowing, shedding problems.

The strength and anti-cracking effect of cement mortar have an important relationship with water. Hydration and coagulation hardening of cement are a gradual and continuous process. The first hydration, the latter condensation, and the hardening hardening result depend on the hydration conditions. The more fully hydrated, the better the water is maintained, and the longer it is maintained, the higher the strength will be, the smaller the shrinkage, and the better the anti-crack effect; the hydration and coagulation hardening rate of the cement will be affected by the ambient temperature. The effect is also obvious: the environment temperature is high, the hydration and hardening speed are fast, and the ambient temperature is low, the cement hydration and the setting hardening rate are correspondingly slow. Early-drying, early-hardening, and early-strength cement mortars, due to poor water retention and poor self-conservation, can cause excessive shrinkage, excessive shrinkage, and large area cracks.

In research and practice, early strength, early hardness, and early strength of cement mortar are inferior to late-dry, late-hard, and late-strength cement mortars because of their late strength, stability, and crack resistance. This is also the reason why cement is used as an inorganic hydraulic material. The specificity of the gelling material is determined.

The occurrence of turtle cracks is mainly related to cement. Regardless of the type of cement, there is a problem of dry shrinkage. From the experimental point of view, the late strength, stability and crack resistance of cement varieties such as sulphoaluminate cement and white cement It is not as good as ordinary Portland cement. The main reason is that these products have high shrinkage, dry shrinkage, strong contraction force, and easy to produce cracks.

Ordinary Portland cement is widely used in China's architectural engineering. It has a history of several decades. Its performance is very good, as long as the hydration is sufficient, the water conservation conditions are good, and its strength is several years or even ten years later. It will be improved. At present, the polymer mortar and cement putty are still based on ordinary Portland cement, and the model used is 32.5R or 42.5R. The amount of the formula in polymer plaster and cement putty must be well mastered.

2, "external factors"

The “external factors” are mainly caused by construction techniques, foundations and the natural environment. Under normal circumstances, the construction design is unscientific and unreasonable, the settlement and deviation of the foundation, the thickness of the one-time wiping during construction, the foundation cracks before construction, the stress caused by earthquakes, large wind pressure, and the continuity after construction High temperature and dry weather can cause cracks. The performance of cracks and cracks is generally more cracks. The shapes are horizontal, vertical or irregular.

There are crack cracks in size, large crack cracks can be easily seen, and small crack cracks are not necessarily visible to the naked eye, but as long as the water is sprayed onto the dry wall, the fine crack cracks can be clearly seen.

Cracks and cracks are basically no reliable materials and technical means can be completely restored, the results will cause great difficulties to the building decoration, decoration, waterproof engineering and future maintenance work, because the cracks and cracks in the outer wall. When the external environment conditions (foundation settlement, earthquake, etc.) and temperature difference and dry humidity change, the size and shape of the gap will also change constantly, that is, the gap between the low temperature in winter and the high temperature in summer will change, that is, in the same season. On rainy days and sunny days, the crevice size will also change. This is also the most vexing thing for cracks and cracks in roofing, walls, underground waterproofing works and maintenance practices. After repairs are made, leakages begin again in less than one year or even several months.

Third, control and prevent crack cracks and technical measures

The above analysis shows that crack cracks originate mainly from two aspects of “internal factors” and “external factors”. The solution to “internal factors” mainly focuses on the production of products and the technical performance of raw materials. The “external causes” are relatively complex and involve To the architectural structure design, construction technology and technical level, project quality supervision and management, natural environment and other aspects.

1. Anti-cracking of polymer plaster and cement putty, focusing on the selection of raw materials, selection of high-quality raw materials, full understanding and understanding of the nature and mechanism of various raw and auxiliary materials, scientific formula, selection of functional, Stable and reliable quality products can better prevent cracks.

2. Architectural design, especially external wall thermal insulation structure design should be rigorous, and problems such as foundation settlement, earthquake resistance, wind pressure resistance, stress release, and environmental impact should be fully considered.

3. In the construction process, in order to avoid the occurrence of large dry shrinkage force on the surface mortar and wall putty, each scraping should be thin and thick, and the trowel mortar should be no more than 2.5 mm thick for each scraping. The external wall putty Wipe no more than 1MM layer thickness.

4. It is not advisable to excessively or excessively use polyvinyl alcohols, latexes and other highly-sealing adhesives in dry-mixed surface mortar, external wall putty, or common cement. Such adhesives can rapidly form and close cement pores and increase The cement generates shrinkage force, forms a "crust" phenomenon, and forms a large strength difference with the base layer, that is, the strength of the surface layer greatly exceeds the strength of the base layer, easily causing cracking, emptying, and falling off. In addition, once the micropores of the cement mortar are completely closed, this will not only affect the full hydration of the cement, but also will cause the cement mortar to lose its “free breath” and self-conservation function. The undesirable components in the wall cannot be released through the micropores with water. The wall life will be poor.

5. The design and construction of the external wall thermal insulation layer did not take into account the release of the internal stress of the thermal insulation layer. The entire wall surface was built up from the top to the bottom and several tens of floors. No expansion joints were designed. Once a large stress was generated, The entire insulation layer is trowel mortar, exterior putty, paint layer will inevitably produce cracks.

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