Zhang Longfang (Jiamusi Xingcheng Group, Jiamusi, Heilongjiang 154000), if the penetration of water has a detrimental effect on the destruction of the insulation system and on the senses of the residents and the mind. Due to the quality of residential projects, there are more and more disputes or lawsuits involving thermal insulation wall cracks, etc. The cracks in buildings have become a very intuitive and sensitive issue and a primary quality requirement for the tenants to judge the safety of buildings. Therefore, strengthening the study of the thermal insulation wall structure, especially the research on the anti-cracking measures of the thermal insulation wall, has become a topic of common concern for the national administrative departments and the design, material production, construction, and housing developers.
With 0.05mm as the boundary, cracks smaller than 0.05mm are called microscopic cracks, and cracks larger than or equal to 0.05mm are called macroscopic cracks.
1 Basic principles of crack control for exterior wall insulation surface 1.1 The external insulation system is superior to the internal insulation system in anti-cracking. The external thermal insulation system is conducive to the building to establish a more reasonable temperature field, so that the winter temperature of the main structure in the insulation layer increases, the humidity decreases, the temperature changes more smoothly, the temperature stability of the structure increases in the summer, and the thermal stress of the wall structure decreases. And the effects of rain, snow, freezing, thawing, dryness, and humidity on the main wall will be greatly reduced, so that the risk of cracks, deformation, and breakage of the main wall will be reduced, and the building life will be greatly extended. Therefore, the external thermal insulation system is superior to the internal thermal insulation system in protecting the building structure and preventing the occurrence of cracks.
1.2 Layer-by-layer gradient flexible release stress "The principle of anti-crack technology. The use of layer-by-layer gradient, flexible release stress crack resistance technology" concept of structural design points are: thermal insulation system adjacent layers of performance, elastic modulus change indicators Matching, layer by layer gradient, cracking mortar should ensure a certain degree of flexibility in order to release the deformation stress. At the same time, the use of soft reinforcement and a variety of fibers in the anti-crack protection layer change the direction of stress transmission to prevent the occurrence of various stress concentrations. When coating finishes, the ideal mode should be that the flexible deformability of coatings from the crack-resistance mortar layer one by one should be gradually increased; when facing the tile surface, the flexible adhesive glue and the hooking glue should be used.
1.3 Ordinary cement mortar should not be used as the leveling and protective layer material on the surface of the insulation system. Ordinary cement mortar not only easily produces a variety of shrinkage cracks, but also due to poor flexibility and can not adapt to its own temperature differential deformation and the stress generated by the adjacent layer temperature deformation, use it as a protective layer of the insulation layer, easy to produce cracks, thickness The thicker the more serious.
1.4 No cavity or small cavity structure to improve the stability of the system. No cavity or small cavity construction method makes the external thermal insulation system have the advantages of strong wind pressure resistance, good system integrity, stable stress transmission, and good safety. In the high-rise building works for external thermal insulation, it should pay full attention to the damaging effect of wind load on external thermal insulation, use as much as possible no cavity or small cavity to meet the requirements of wind pressure destruction. Because the destructive force of wind pressure on a building is proportional to the height of a building, a high-rise building has a higher wind pressure than a multi-storey building. Therefore, the wind pressure should be taken into account in the external insulation of high-rise buildings, and the negative pressure must be taken into consideration. influences.
1.5 The principle of compatibility and compatibility of materials in each layer should be fully considered. Since the heat preservation system is composed of multiple layers of materials, the crack resistance performance should be considered in addition to the functionalities of the materials of each layer, and the compatibility and matching of the materials should be fully considered.
1.6 Strengthen the sealing principle of material change at the insulation cut-off part. In the material transformation of the insulating layer and other materials, due to the difference in density of these materials is too large, which determines the elastic modulus and linear expansion coefficient between the material is not the same, the deformation under the effect of temperature stress is also different, Surface cracks can easily occur at these locations. At the same time, the water repellent treatment of these parts should also be considered to prevent water from intruding into the insulation system and to avoid damage to the system due to frost heave, affecting the normal service life of the system and the durability of the system.
2 External wall insulation surface crack control technology 2.1 External wall thermal insulation structure design 2.1.1 Single internal insulation is not conducive to the protection of structural walls, should avoid the use of a single internal insulation design.
2.1.2 If inner insulation is required, it is best to use the internal and external insulation compounding method. Inner insulation is used on the inner side of the outer wall, inner partition and other parts. It is better to use internal insulation with crack resistance, fire resistance and sound insulation; then In the outside of the external wall, external insulation is used for crack resistance, waterproof, weather resistance, fire resistance, wind pressure resistance, and shock resistance.
2.2 Polystyrene thin plastering external thermal insulation structure design 2.2.1 polystyrene board thin plaster external insulation. This type of external insulation has a relatively fixed structural design. Due to the deficiencies of large cavities, poor heat insulation and poor fire performance, the scope of application of this system is limited. Foreign countries are limited to 18 or 22 meters of buildings for fire protection considerations. However, taking into account the application of the system in China earlier and more, China's current fire protection regulations do not have explicit restrictions on it.
2.2.2 Improved polystyrene board thin plaster external insulation. Improvements are reflected in the installation of fire barriers and the conversion of large cavities into voids or small cavities.
2.3 Cast-in-place Polyphenylene Board External Thermal Insulation Structure Design 2.3.1 The problem of insufficient adhesion between the polyphenylene plate and the concrete base wall is solved by adopting a polyphenylene plate with a pull groove and an interface mortar treatment. The polyphenylene plate has good adhesion with concrete after being treated with interface mortar, while the pull-slot groove is partially embedded in the concrete, the pull-node effect is very obvious, and the overall safety is enhanced.
2.3.2 Leveling, auxiliary heating, and leveling of the slurry through thermal insulation of polystyrene powder to solve the problems of flatness, verticality, thermal bridge, partial damage and cracks. With the summary of construction technology, flatness is usually controlled by using Panasonic Tightening and adjusting the angle of inclination of the template when tying the polyphenylene sheet, but this method has a large effect and individual differences, and it is difficult to completely solve the problem. Another method is polishing, which is to polish a part of the outstanding polystyrene board to meet the flatness requirements.
2.4 Steel wire frame insulation board insulation design 2.4.1 Traditional steel mesh insulation board insulation design. Because this type of system uses 20imm30mm thick ordinary cement mortar for leveling, cracking phenomenon is more common, so almost do not dare to do paint finish, but paste the tile, so that the increase in unsafe due to excessive load. In particular, after the 65% energy-saving work was carried out, the torque exceeded the safe torque requirement due to the increased thickness of the insulation layer. Therefore, such practices should be improved.
2.4.2 Improved design of external thermal insulation structure of steel wire grid insulation board.
a After the completion of the casting, the surface of the steel wire frame polystyrene board is leveled with 20mim'30mm powdered polystyrene particles, which can greatly reduce the load. At the same time, due to the blocking of the thermal bridge, it has a good effect of supplementing the heat insulation, reducing the Torque increases safety. b. Using dual mesh construction to enhance crack resistance. When coating finishes, anti-cracking mortar composite alkali-resistant glass fiber mesh cloth is used as anti-cracking protective layer on the leveling layer of glue powder polyphenyl particle insulation slurry; when using tile facing, the polystyrene powder granular insulation slurry The anti-cracking mortar composite hot-dip galvanized steel wire mesh (with the insulation layer steel wire frame binding) is made on the leveling layer as the anti-crack protection layer and the paste surface tile base layer.
2.5 Insulation and Thermal Insulation External Wall External Insulation System Design. Insulation pastes have many types of external thermal insulation systems and their quality is uneven. The quality of the external insulation system has exceeded that of similar products in Germany, but poor quality systems are also flooding the market. At present, the competent authorities of the State and Beijing Municipality have strengthened market supervision. In addition to the preparation of industry-standard plastic polystyrene polystyrene insulation systems, other insulation pastes have been restricted and eliminated, and should be treated differently in design.
2.6 Facing brick exterior insulation and thermal insulation system design 2.6.1 In the alternative, paint exterior insulation system should be the first choice. When selecting the tile facing system, it is necessary to ensure that the system meets the following conditions: a. a bonded brick with a reliable connection with the base wall; b. the system structure should fully consider the temperature stress and other deformation stress absorption and release; c. Insulation materials should have good heat radiation and anti-fire performance; d system should have strong resistance to wind pressure, weather resistance, the system must pass large weather resistance test and seismic test validation; 2.6.2 in the external insulation system paste tile Should pay attention to: a should not be directly on the polythene board thin plastering system paste tiles; b. should not be in the core thickness of more than 75mm thick paste ordinary cement mortar steel wire mesh polystyrene board exterior insulation system facing tiles. c. It is advisable to use a double-mesh structure of steel mesh heat insulation board with plastic powder polystyrene granules to maintain a leveling paste. d. It is recommended to select the outer wall exterior insulation paste floor tile veneer system.
As the external thermal insulation system is a non-load bearing composite wall surface, the damage of the wall cracks does not lie in the structural safety, mainly the aesthetic and psychological impact on the occupants and the existence of cracks, which may cause damage to the thermal insulation system (such as water Penetration, freeze-thaw damage, etc.). Seen from the infiltration of water, water molecules can pass through any visible cracks, so theoretically it is not allowed to crack. Due to the development of cracks, the determination and classification of cracks should include time, width and length of cracks, and area incidence.
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