Research on Crack Control Technology of Vitrified Microbead Insulation Mortar External Wall Insulation System
Research on crack control technology of vitrified micro-bead insulation mortar external wall insulation system Yuan Bo, Li Zhu (School of Architecture and Civil Engineering, Taiyuan University of Technology, Taiyuan 030024, China) Main diseases. Based on this, the basic principles of crack control of vitrified micro-bead insulation mortar external wall insulation system are introduced. The causes of cracks are analyzed and analyzed. The base wall, insulation layer, anti-crack protection layer and decoration of this type of insulation system are proposed. Technical measures for crack control of the surface layer. It has been proved by practice that these measures have obvious effects on avoiding cracks and promote the development and application of vitrified microbead insulation mortar external wall insulation technology.
The vitrified micro-bead insulation mortar external wall insulation system has been widely used because of its excellent weather resistance stability, excellent thermal insulation, Class A fire protection, small thermal stress deformation, good construction performance and environmental protection. In the wall insulation system. However, the external thermal insulation technology of vitrified micro-bead insulation mortar is to place the thermal insulation system on the outer side of the outer wall. In addition, the construction process is complicated, and the engineering quality problem is increasing. The most influential problem is the cracking of the surface layer.
1 Basic principles of crack control technology 1.1 Insulation system materials Complete supply of external wall insulation system After passing the system material performance test (safety, weather resistance) inspection, the complete supply is qualified, which is beneficial to ensure the matching of the system materials and achieve the crack resistance requirements. Thereby improving the stability of the external wall insulation system and extending its service life. 2011-)5-)5 Fund Project National Natural Science Foundation of China (50778118): Shanxi Province Natural Science Foundation Yuan Bo, Master of Architecture and Civil Engineering, Taiyuan University of Technology, Room 423024, Building 12, Yingxi Campus, Taiyuan University of Technology, Telephone: 1.2 material layer by layer gradient, deformation stress layer by layer release vitrified microbead insulation mortar outer wall insulation system the outermost layer is in direct contact with the external environment, the temperature difference is greater than the temperature difference of other structural layers, the sharp change of temperature difference has produced Concentrated temperature stress, outer layer deformation is greater than inner layer deformation. For this reason, the elastic modulus and linear expansion coefficient of each adjacent structural layer material should be coordinated with each other, and the deformation ability should be matched with each other to gradually release the stress. In addition, each structural layer and material layer of thermal insulation should have a certain flexibility, and can effectively release stress under deformation conditions. If the deformation ability of adjacent layers differs greatly, a flexible release stress transition layer such as a flexible putty layer should be provided. Therefore, the constraining ability and the anti-constraint ability of each adjacent structural layer are sufficiently small to avoid or reduce the constraint tensile stress and prevent crack generation.
1.3 block and block, the waterproof and ventilated building exterior wall area is as large as possible. In order to prevent the external wall insulation system from cracking, it should be considered to be divided into blocks. The flexible joint material with strong deformation ability can be embedded in the gap; the insulation system is crack-proof. Under the premise, it should be waterproof and breathable. In order to prevent or reduce the infiltration of indoor water vapor and rapidly discharge the water vapor in the thermal insulation layer, a gas barrier layer may be disposed inside the thermal insulation layer; in addition, the water vapor molecules can smoothly escape from the thermal insulation layer under the action of the partial pressure difference. The water vapor permeation resistance of the material outside the insulation layer should be reduced.
1.4 Pay attention to the design of the key nodes of the thermal insulation system. Pay attention to the thermal insulation design of the inner side of the parapet wall to take insulation measures on the inner and outer sides of the parapet wall to avoid cracks in the parapet wall.
Pay attention to the structural design of the insulation parts such as balconies, awnings, air conditioners, outdoor partitions, etc., which are all obvious parts of the thermal bridge. The temperature stress causes cracks in the joint between the part and the main part.
Strengthening the insulation cut-off part or material transformation joint design Because the elastic modulus and linear expansion coefficient of various materials are different, the deformation caused by temperature stress is different, it is easy to crack, moisture invades from crack, and the system is destroyed due to frost heaving, affecting The normal service life and durability of the insulation system.
Pay attention to the energy-saving design of structural expansion joints. The wall on both sides of the expansion joint is a large part of the heat dissipation in the envelope structure, and insulation measures should be taken.
2 Crack control technology 2.1 The main structure of the base wall building in the construction stage is caused by the shrinkage of the concrete due to the effect of cement hydration heat and external air temperature; or the difference between the basic design load and the foundation construction quality after completion. If the crack occurs on the outer wall of the building, the wall will be transferred to the external thermal insulation system when the crack occurs on the outer wall of the building. In addition, the surface of the base layer is too dry or too wet, or there is grease. , the release agent and other adhesions that hinder the adhesion, or the surface flatness deviation is too large (deviation 1mm), under the action of temperature deformation, repeated freeze-thaw cycles, negative wind pressure, etc., will form an empty drum, cracking.
The surface of the base layer should be cleaned with grease stains, mold release agents and other adhesives that hinder the adhesion. Remove 10mm protrusions and loose and weathered parts on the wall surface, fill and compact the main structure deformation joints, expansion joints and other holes, and its verticality and flatness. The degree shall meet the requirements of the construction acceptance specification; the surface layer shall not have chalking, peeling, ashing, and pan-alkali.
The surface treatment of the base layer is to prepare the interface mortar, the medium sand and the cement into the interface mortar according to a certain mixing ratio, and uniformly coating the surface of the outer wall with the paint roller is the most common treatment method for the surface of the base layer, wherein the original strength of the interface mortar is 0.7 MPa. Water resistance is 0. 5MPa, freeze-thaw resistance is 0.5MPa. Interface mortar and base wall must be firmly bonded, without delamination, drum and crack, bonding strength is 0. 1MPa, interface mortar should not be too thick, often using brushing method . In addition, when the interface mortar is under construction, the surface of the base layer should not be too dry.
2.2 Insulation layer The vitrified microbead insulation mortar insulation layer is made up of inorganic light aggregate vitrified microbeads, cement, fly ash and various composite additives in a certain proportion. The performance index is: dry density 矣300kg/m3 , wet density 1000kPa, tensile strength 3100kPa, linear shrinkage 矣0.3%, initial setting time 1.0h, final setting time 矣2.0h. Softening coefficient 0.6, thermal conductivity 矣0. K), heat storage coefficient 0.95WKm2K), burning Performance level A. The main reasons for the cracks in the insulation materials are as follows: (1) The interface mortar on the surface of the base layer is too thick, so as to meet the flatness requirement of the insulation layer, the thickness of the local insulation mortar is too large, thus increasing the water shrinkage and temperature and humidity changes of the insulation mortar. The generated stress causes empty drum and cracking; 2 the thermal insulation mortar is too thick at one time, and the crack is also caused by the temperature and humidity change; 3 the slurry is in the process of on-site production, if the mixing ratio is not well controlled, the bonding is made The vitrified microbead insulation mortar has poor workability, easy to shrink, easy to slip or excessive adhesion.
For this reason, according to the requirements of G144-2008 for external thermal insulation engineering technical regulations, the following measures are taken in the construction of thermal insulation layer to reduce the cracking of the thermal insulation layer.
The mechanical stirring was used, and the stirring time was 35 mm to make the slurry into a uniform paste. The hot insulation slurry mixed with water should be used up within 1h, and the floor material should not be recycled and used twice.
Before the construction, the wall should be vertical, the formula should be found, the thickness control line should be pulled, the vertical and horizontal lines should be pulled, and the sleeve should be used as the mouth. The slurry should be used as the standard gray cake or blasting according to the thickness line. During construction, avoid sun exposure and construction of windy weather above 5, and the ambient temperature is 5 ° C. In order to ensure the quality of plastering, the thermal insulation slurry should be plastered with grading. The thickness of the first plaster should be controlled within 25 mm. The plastering and hardening can be carried out for the next time. The final control should be 5 ~ 10mm, and the thickness of the gray cake or the blasting should be reached, and the big bar should be flattened, the iron plate should be calendered, and the verticality and flatness should be satisfied. Construction quality acceptance procedures are required. The bottom layer of the construction thermal insulation paste should be plastered from top to bottom, from left to right, and wiped to a distance of about 10 mm from the insulation standard cake.
In order to reduce the shrinkage of the insulation layer and ensure the strength of the insulation layer, the insulation layer is cured after the construction of the thermal insulation slurry is completed. The natural maintenance of the thermal insulation slurry should be done within 24 hours after construction. It is strictly forbidden to flush, impact and vibrate. After 24h, the water is maintained and the watering time is 3d. If the construction interval between the two layers of thermal insulation mortar is greater than 1d, the insulation layer should be layered and cured. . After the insulation layer is solidified and dried, the protective layer of crack-resistant mortar can be applied. It usually takes 3~7d. 2.3 Anti-crack protection layer The anti-crack protection layer is composed of crack-resistant mortar and reinforcing mesh, which plays a key role in the crack resistance of the whole system. If the crack occurs in the crack-resistant protective layer itself, it will affect the durability and safety of the entire insulation system. The anti-cracking mortar is a kind of mortar mixed with polymer, fiber and admixture. Its performance index has a tensile bond strength of 0.7 MPa during operation time of operation 1. 3 tensile bond strength (normal temperature 28 d) 0.7 MPa; 4 immersion Ten-layer cement with tensile bond strength (normal temperature 28d, water immersion 7d), and should meet the requirements of general Portland cement GB175-2007; sand should meet the requirements of ordinary concrete sand quality standards and inspection methods G52-2006, screening> 2.5mm granules, containing mud content <3%. The reinforcing net consists of alkali-resistant glass fiber mesh and galvanized steel mesh. When the finish layer is coated, it is made of alkali-resistant glass fiber mesh. Its performance is: 1 unit. Area mass 160g/m2; 2 alkali-resistant breaking strength (warp and weft) 750N/50mm; 3 alkali-resistant breaking strength retention rate (warp and weft) 50%; 4 elongation at break (warp, weft) 矣5 0%; 5 plastic coating amount 20g / m2; 6 glass composition (mass) should comply with the requirements of alkali-resistant glass ball C719-1990. A galvanized steel mesh is used when the finish is a tile. Under the joint action of polymer mortar and reinforcing mesh, it can not only resist its own shrinkage, temperature and humidity deformation, but also neutralize the deformation caused by the base layer and the insulation layer, thus ensuring the crack resistance requirements of the protective layer.
During construction, the thickness of the anti-cracking mortar layer should be controlled at 35 mm. The thickness is too thin and the strength is not enough. The thickness is too thick, which not only increases the cost, increases the load, but also greatly increases the possibility of shrinkage and cracking of the surface layer.
After the anti-cracking mortar is finished, it is strictly forbidden to apply ordinary cement mortar waist line, mouth line or scraping rigid putty on this surface layer, otherwise the surface layer will be cracked. After the surface layer reaches a certain strength, 7d watering maintenance is required. . Construction in the rain is strictly forbidden, and reliable rain protection measures should be taken during the rainy season.
The external thermal insulation system is added to the reinforcing mesh, and the purpose thereof is to effectively disperse the stress of the crack-resistant protective layer and increase the tensile strength thereof. During the construction, the reinforcing net should also pay attention to straightening, flattening, and close to the outer surface of the plastering mortar. The fullness of the mortar reaches 100%, and the surface is not exposed to enhance the net, so that the reinforcing effect can be fully exerted. 1 Alkali-resistant glass fiber mesh cloth should be laid in the plaster mortar near the side of the facing layer, the paving rate should reach 100%; the alkali-resistant mesh cloth around the door and window openings should be turned out 100mm, and at the four corners A 400mm×300mm alkali-resistant mesh cloth is laid in the 45° direction, and the alkali-resistant mesh cloth is only docked and not overlapped; when the mesh cloth is overlapped, the mesh width of the mesh cloth should be 100mm, and the overlap The place should be filled with mortar, and it is strictly forbidden to dry it, which can greatly reduce the probability of cracks. 2The galvanized steel wire mesh is generally sectioned for vertical paving, and is laid flat in the order of first down and then on. The steel mesh at the corner of the corner shall not be broken, and the edge of the mesh shall be covered by the angle net; galvanized steel mesh The paving length is m3m, the horizontal and vertical overlapping width should not be less than 2 grids, the number of overlapping layers is 矣3, the lap joint is fixed with anchors, the anchors are used at 710/m2, and the 4 layers are overlapped. Partially cut off 2 layers; anchors are placed on the surface spacing of 500mm×500mm; a 600mm additional galvanized steel mesh is subsidized in the 45° direction at the corners of the door and window openings for local reinforcement, and the steel mesh is fixed in a large area.
The external thermal insulation system shall be provided with anti-cracking and dividing joints as necessary. The horizontal crack-resistant joints should be set according to the floor; the vertical crack-resistant joints should be set according to the wall area, and should not be larger than 30m2 in the panel construction. The width of the joints is 矣50mm, which should be constructed by on-site molding. The specific method is to open the slot on the insulation layer. The size is 10mm wider than the design requirement and 5mm deep. It is embedded with crack-resistant mortar, and the alkali-resistant mesh cloth should be overlapped at the joint seam. When the alkali-resistant mesh cloth is lapped, the upper edge of the application is pressed along the alkali-resistant mesh cloth, and the lap width should be the width of the division slit.
2.4 Finishing layer According to the technical specification of vitrified micro-bead insulation mortar, DB04-250-2007 standard, the finishing layer is divided into two types: paint finish and face tile finish. For the paint finish layer, the use of rigid water-resistant putty or paint and putty does not match the deformation of the crack-resistant protective layer and crack; in high temperature weather, the construction surface layer is dehydrated due to insufficient water retention performance, causing cracking; When the putty layer has not been dried or has just been rained, the high-elastic surface coating with poor ventilation is directly applied on the top layer, causing the surface coating to be air-blasted. The crack in the facing surface of the tile is due to the deformation stress generated by the thermal stress of the tile facing layer, which is not released, and the hollowing is easy to occur; before the bonding, the tile needs to be immersed in water or not soaked or the water is not dried before the brick is bonded. Dry, the bonding surface forms a water film, which weakens the bonding force between the mortar and the brick.
Control measures for the cracks in the veneer layer: 1 After the construction of the crack-resistant protective layer of the paint finish layer, the surface is brushed with a waterproof and breathable elastic primer. After the protective layer is basically dry, the flexible putty is scraped twice to make the surface smooth and smooth. After the surface is dried, an elastic coating is applied. In order to prevent the occurrence of cracks, the quality acceptance of the paint finish layer shall comply with the relevant requirements of the quality acceptance specification GB50210-2001 of the building decoration and decoration project. It is strictly forbidden to use the surface brick with large water absorption and no groove when constructing the surface of the two-faced brick. The brick should not be sealed with sealant and should be made of special ceramic tile adhesive for external insulation (compression ratio 矣3, linear shrinkage 矣0.3%, Deformability > 5%) and a 20 mm expansion joint at a height of every 1618 m, caulking with polyurethane or silicone glue.
3 Conclusion The crack of vitrified micro-bead insulation mortar external wall insulation system has become an important disease affecting its quality. This paper mainly analyzes the external thermal insulation of vitrified micro-bead insulation mortar from the design itself, thermal insulation materials and on-site construction process control. The reason for the crack in the surface layer is proposed, and preventive measures are proposed to reduce the probability of crack occurrence, thereby improving the service life of the vitrified microbead insulation mortar outer wall.
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