Release Time:2022-04-20 17:06:15 Hit Count:682
1. Development of prefabricated buildings in China
The development of prefabricated buildings is a key policy supported by China in recent years. It can save energy, reduce environmental pollution and greatly improve the quality and safety level of production. Prefabricated buildings are also widely used in Germany. Most of the houses in their country adopt the structure of shear wall, concrete and laminated plate, because the durability of concrete structure is very good when combined with PC component assembly. The residential structure is also based on concrete assembly, which reduces the construction cost and improves the operability of construction. China has also issued a series of guidelines and policies in recent years. Our country is also vigorously developing prefabricated buildings, indicating that the development of the construction industry needs to be upgraded. Although it is still in its infancy, the development prospect of prefabricated buildings will be very good through the continuous progress and improvement of technology and level.
2. Characteristics of grouting sleeve
Grouting sleeve refers to that after the ribbed reinforcement is inserted into the sleeve, the special grouting material is filled with the gap between the sleeve and the reinforcement. After hardening, the grouting material forms a close engagement with the transverse rib of the reinforcement and the inner wall of the sleeve, so as to realize the effective force transmission between the reinforcement and the sleeve and achieve the performance of class I joint.
Grouting sleeve is a common connection method for reinforcement recommended by China's prefabricated building code. The technology of grouting sleeve is mature and applicable to a wide range. The connection technology forms a rigid joint at the connection part. The joint structure has the mechanical performance similar to that of cast-in-situ joint, and can be applied to the connection of large-diameter reinforcement. However, the technological process of grouting sleeve is complex, the construction is difficult, and the cost of sleeve and grouting material is high. Due to the difficulty of quality inspection of grouting sleeve connection, there are high requirements for the quality of grouting sleeve at the connection node, the production accuracy of prefabricated components, and the organization and management of installation and construction.
3. Grouting connection mechanism of prefabricated building reinforcement sleeve
3.1 the principle of full grouting reinforcement sleeve grouting connection sleeve grouting connection technology is to use the concave convex part in the sleeve, insert two reinforcement to be connected from the end, and the grouting machine injects high-strength grouting material from one end of the grouting opening. The grouting material has the performance of shrinkage and slight expansion. Therefore, after the grouting material is hardened, the reinforcement and the sleeve are tightly combined into a whole, which is precisely due to the nature of the grouting material, The compactness inside the sleeve is ensured. Under the constraint of the sleeve, the reinforcement is also bonded firmly, so this connection method has high tensile and compressive strength and connection reliability.
Reinforced sleeve full grouting connecting member
3.2 semi grouted reinforcement sleeve grouting connection semi grouted sleeve connection. One end of the reinforcement is screwed with the thread of the sleeve, which is the bite between the threads to bear the stress to be transmitted, and the other end is the connecting reinforcement, which is poured with non shrinking cement-based mortar. After hardening, the friction between the three caused by the bite between the reinforcement and the grouting material, the grouting material and the sleeve is used to transmit the force, and the two reinforcement achieve the connection.
Semi grouted connecting member of reinforcement sleeve
4. Process flow and key points of operation
The construction process of grouting sleeve in precast beam column joint area is as follows: foundation treatment → grouting cavity sealing → grouting construction preparation → grouting → plugging grout discharge hole → final inspection.
1) Basic treatment. Before construction, the foundation shall be cleaned and flushed within a few hours before slurry sealing. The joints shall be flushed and wetted with pressure pipes to ensure that there is no ash, oil stain and ponding.
2) Grout chamber seal. Special high-strength sealing material is used as sealing material. The sealing material is used to form a closed groove space at the bottom of the component by setting slurry, and the space is connected with the reserved hole channel and sleeve hole at the lower part of the component.
3) Grouting construction preparation. The grouting material corresponding to the working condition and determined to be qualified shall be used. Before construction, add water and mix for 3 ~ 5 min. The ratio of grouting material to water is 1: (0.125 ~ 0.135), and then stand for 2 ~ 3 min until the bubbles are discharged naturally. The grouting machine shall be moistened with clean water in advance.
4) Grouting. Pour the grouting material into the grouting machine and start grouting after circulating for several times. When the mixed grouting material is poured into the grouting machine, it shall pass through the filter screen to prevent the grouting machine from blocking. The grouting material is injected from the grouting opening of the grouting sleeve, and the grouting flow rate is 0.8 ~ 1.2 L / min. 5) Block the slurry discharge hole. After the mortar flows out of the grout outlet of the grouting sleeve, immediately block the grout outlet with a rubber plug. After checking and confirming that all joints have completed grouting, the surfaces of grouting opening and outlet shall be leveled, and the grouting process shall be recorded on site.
5. Analysis of factors affecting the performance of grouting sleeve
The mechanical properties of grouting sleeve joints will have defects due to the influence of sleeve, grouting material quality and construction quality. The loose sealing of grout sealing layer, grout outlet and grout outlet and air interlayer can lead to cavities at the top or middle of the sleeve. The dimensional deviation of prefabricated components will lead to the eccentricity of components and sleeves and poor slurry flow. If the construction time is too long after the grouting material is mixed, the fluidity of the slurry will be reduced, the stress transmission in the sleeve will be affected, and the stress performance will be reduced. The control of construction effect can be enhanced through personnel control, quality control and other measures to ensure the quality of construction.
At present, the state vigorously develops prefabricated buildings and makes a fundamental change in the construction mode, from extensive to industrialized production and construction mode. At this stage, the development level of domestic fabricated buildings is not high, and the connection of fabricated building reinforcement still has broad development space. The connection between fabricated integral structural reinforcement is the key to ensure the force transmission between reinforcement and the overall performance of the structure, and it is also the key to the development of fabricated buildings. Different connection forms directly affect the project quality, cost and construction period. Therefore, the development of reinforcement will be in the following aspects. 1) The cost is reduced, the material is easy to obtain and the performance is improved. With the use of high-strength steel bars in buildings, the corresponding connection technology should also be strengthened. The renewal of materials is the foundation of technological progress. The research and development of high-performance materials is conducive to the development of high-strength reinforcement connection technology. 2) Simple structure, small operation space and convenient construction. According to the engineering practice, it is found that the simpler the structural form is, the more convenient the construction is, and the connecting components are easy to process and popularize in large quantities. 3) Reinforcement connection technology is developing towards standardization, modularization and informatization, with unified specifications and convenient mass production in factories.
