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The cracking and cracking of cement-based mortar and putty is a common problem with common problems. In many years of research and practice, Tianrun Gome believes that the causes of cracks and cracks in plastering mortar and exterior wall putty mainly come from the two aspects of “internal cause†and “external causeâ€.
1 "internal cause" aspect
The "internal cause" is mainly due to the fact that some plastering mortars and putty products have large shrinkage and quick shrinkage, and large internal stresses cause damage to the mortar structure and cause cracks. The cracks generally exhibit irregular cracks. It is often said that the cracks of the turtle are mainly due to insufficient understanding of the nature, function and technical principle of the raw materials. The raw materials used do not meet the requirements, and the formula is unscientific, resulting in unstable product quality and poor crack resistance. Shortly after construction. There is a large area of ​​cracking, hollowing, and falling off.
The strength and anti-cracking effect of cement mortar are all related to water. The hydration and coagulation hardening of cement is a gradual, continuous process. The first hydration, the subsequent condensation, and the result of condensation hardening depend on the hydration conditions. The more complete the hydration, the better the water conservation, the longer the water curing time, the higher the strength, the smaller the shrinkage, the better the crack prevention effect; the hydration and condensation hardening speed of the cement is affected by the ambient temperature. The effect is also obvious, that is, the ambient temperature is high, the hydration and hardening speed is fast, and when the ambient temperature is low, the speed of cement hydration and condensation hardening is correspondingly slower. Any cement mortar that is dry early, early hard, and strong early, due to poor water retention and poor self-supporting ability, will produce excessive shrinkage, excessive shrinkage, and easy to produce large-area cracks. In research and practice, the late strength, stability and crack resistance of cement mortar with early drying, early hardening and early strength are worse than cement mortars with late dry, late hard and late strength. This is also the cementity of cement as inorganic. The specificity of the cementitious material is determined.
The cracks in the turtle are mainly related to cement. No matter what type of cement, there is a problem of shrinkage. From the test situation, the strength, stability and crack resistance of cement grades such as sulphoaluminate cement and white cement. It is not as good as ordinary Portland cement, mainly because these products have large shrinkage, quick shrinkage, strong shrinkage force, and easy to produce cracks in turtles. Ordinary Portland cement is widely used in China's construction projects. It has a history of several decades, and its performance is very good. After research and experiment, as long as the hydration is sufficient and the water conservation conditions are good, after a few years Even after ten years, its strength will increase. At present, polymer mortar and cement putty are still mainly made of ordinary Portland cement. The model used is 32.5R or 42.5R, and the formula amount in polymer plastering mortar and cement putty products must be mastered.
2 "external causes"
The “external cause†is mainly caused by construction technology, foundation and natural environment. Under normal circumstances, the design and construction of the building is unscientific and unreasonable. The foundation is settling and deviating. The construction is too thick at one time. The foundation before construction has obvious cracks, earthquakes, stress caused by large wind pressure, and continuity after construction. High temperature and dry weather, etc., will cause cracks. The cracks and cracks generally have cracks, and the shapes are horizontal, vertical or irregular.
3. Another characteristic of crack cracks in cement mortar and cement-based putty is that no matter how thick or thin the wipe is, the crack cracks are cracked from the surface to the bottom, which is the most fundamental cause of leakage of the building. Crack cracks vary in size. Large crack cracks can be easily seen. Small crack cracks are not necessarily visible to the naked eye, but as long as water is poured onto the dry wall, fine crack cracks can be clearly seen.
2 "external causes"
The “external cause†is mainly caused by construction technology, foundation and natural environment. Under normal circumstances, the design and construction of the building is unscientific and unreasonable. The foundation is settling and deviating. The construction is too thick at one time. The foundation before construction has obvious cracks, earthquakes, stress caused by large wind pressure, and continuity after construction. High temperature and dry weather, etc., will cause cracks. The cracks and cracks generally have cracks, and the shapes are horizontal, vertical or irregular.
3. Another characteristic of crack cracks in cement mortar and cement-based putty is that no matter how thick or thin the wipe is, the crack cracks are cracked from the surface to the bottom, which is the most fundamental cause of leakage of the building. Crack cracks vary in size. Large crack cracks can be easily seen. Small crack cracks are not necessarily visible to the naked eye, but as long as water is poured onto the dry wall, fine crack cracks can be clearly seen.
4. As long as cracks and cracks appear, basically no reliable materials and technical means can be completely repaired. The result will cause great difficulties for building decoration, decoration, waterproofing and future maintenance work. The cracks are changing with the external environmental conditions (foundation settlement, earthquake, etc.) and large temperature difference and dry humidity. The size and shape of the cracks also change continuously, that is, during low temperature in winter and high temperature in summer. The gap size will change, that is, in the same season, rainy days and clear days, the gap size will also change, in short, 24 hours a day is changing, which is also cracks, cracks in roofing, wall, underground waterproofing engineering and maintenance practice It is also the most troublesome thing, often after the repair, less than a year or even a few months, began to leak again. As long as there are no cracks and cracks, under normal circumstances, there will be no leakage of water in the building. Anyone who knows the cement pool will understand that as long as there are no cracks, the cement pool will not leak.
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