Concrete specifications, concrete pouring specification requirements

Code for Design of Concrete Structures (Partial Revision in 2015) GB50010-2010; Code for Acceptance of Construction Quality of Concrete Structure Engineering GB50204-2015. These two specifications are the latest national standard versions, one design specification, one construction acceptance specification, and two supporting books.

1. The quality acceptance of the cast-in-place structure should be carried out after the demoulding and before the concrete surface is not corrected and decorated, and a record should be made.

2. For the content that has been concealed and cannot be directly observed and measured, the acceptance record of the concealed project can be checked.

3. The structural components or parts of the trimming or rework should have text and image records before and after implementation.

Extended information: As a traditional material, concrete has always played an important role in the construction industry, and China's concrete output has exceeded the sum of other countries in the world for several consecutive years.

Nearly two-thirds of the world's concrete is produced and used in China, and China's per capita concrete consumption reaches 4 tons per year.

Such a huge amount of concrete has built countless bridges, dams and buildings, but the losses and safety hazards caused by the short life of concrete, salt and alkali tolerance, cracking and other reasons are like a time bomb.

At present, there are a series of worldwide problems in concrete: first, the tensile strength is low, and if it is subjected to tensile stress, it is easy to crack; At the same time, in order to conserve resources and improve performance, a large amount of industrial waste is used as concrete raw materials, and these new materials are more prone to cracking than traditional concrete.

Secondly, in the eastern coastal and northwest inland areas of China, infrastructure construction, such as cross-sea bridges, salt lake poles, etc., the external environment of high salt and high alkali is inevitable.

The normal life of concrete is about 50 years, and during the period of rapid economic development in China, infrastructure construction and the construction of major national projects have put forward higher standards for civil engineering materials.

It is hoped that the requirements of the "Centennial Plan" can be met, "especially some super-large projects, such as the Three Gorges of the Yangtze River, the Beijing-Shanghai High-speed Railway, the Hangzhou Bay Bridge, etc., foreign technology can not meet the needs of these projects for key technologies, which requires us to independently develop." ”

During the interview, Liu Jiaping, vice president of Jiangsu Academy of Architectural Sciences and deputy director of the State Key Laboratory of High Performance Civil Engineering Materials, introduced the background of the preparation for the establishment of the laboratory to reporters.

In addition to the national construction needs, the durability of concrete has also become a key consideration at the beginning of the construction of the laboratory. Liu Jiaping pointed out that durability is the ability of concrete to resist the action of various damaging factors during use.

The durability of concrete determines the life of concrete engineering, and it is an important property of concrete, so it is highly valued by the industry.

The concrete strength grade of plain concrete structure should not be lower than C15; The concrete strength of reinforced concrete structures should not be lower than C20; When using the steel bar with a strength grade of 400MPa and above, the concrete strength grade should not be lower than C25. The concrete strength grade of the prestressed concrete structure should not be lower than C40 and should not be lower than C30. Reinforced concrete elements subjected to repetitive loads should not have a concrete strength class of less than C30.

The requirements of the concrete pouring specification are as follows:

1. Before pouring, the formwork should be watered and moistened, and the cleaning port of the wall and column formwork should be closed after removing debris and stagnant water.

2. The free falling height of the concrete falling from the mouth of the bucket shall not exceed 2 meters, and measures must be taken to add string cylinders when it exceeds 2m.

3. When pouring vertical structural concrete, if the pouring height exceeds 3m, string cylinders, conduits, chutes or door openings on the side of the template should be used.

4. When pouring concrete, it should be carried out in sections and layers, and the pouring height of each layer should be determined according to the structural characteristics and the density of steel bars. Generally, the layering height is several times the length of the acting part of the plug-in vibrator, and the maximum is not more than 500mm, and the layering thickness of the plate vibrator is 200mm.

5. The plug-in vibrator should be plugged in quickly and slowly, and the insertion points should be evenly arranged, moved point by point, and carried out in order, without omission, so as to achieve uniform vibration. The moving distance is not more than the multiple of the radius of the vibrator (generally 300 400mm). When vibrating the previous layer, 50mm should be inserted into the concrete surface of the lower layer to eliminate the joints between the two layers.

The spacing of the plate vibrator should be such that the plate of the vibrator covers the edges of the vibrated part.

6. The pouring concrete should be carried out continuously. If intermittent intervals are necessary, the intervals should be kept as short as possible. And the secondary layer of concrete should be poured before the initial setting of the previous layer of concrete.

The maximum time of the break should be determined according to all cement varieties and the initial setting conditions of concrete, and generally more than 2 hours should be treated according to the construction joint.

7. When pouring concrete, special personnel should be sent to observe whether there is displacement deformation or blockage of formwork reinforcement, reserved holes, embedded parts, inserts, etc., and the pouring should be stopped immediately if the problem is found, and the trimming should be completed before the initial setting of the poured concrete.

The concrete pouring specification has requirements such as keeping the formwork clean and free of stagnant water.

The specifications for pouring fair-faced concrete are as follows:

1. Before pouring fair-faced concrete, the formwork should be kept clean and free of stagnant water.

2. When pouring vertical components, the interval of layered pouring should be strictly controlled. The thickness of the layer should not exceed 500mm.

3. Fair-faced concrete should be poured from both sides at the same time at the openings of doors and windows.

4. The fair-faced concrete is vibrated evenly, and it is strictly forbidden to leak vibration, over-vibration, and under-vibration; The depth of the vibrating pump inserted into the surface of the underlying concrete is greater than 50mm.

5. Before the follow-up fair-faced concrete pouring, the loose stone or floating slurry layer at the construction joint should be removed, and it should be cleaned up after removal.

Concrete pouring working conditions:

1. The formwork, steel bars, embedded iron parts and pipelines of the pouring concrete layer have all been installed, and they have passed the inspection and met the design requirements, and the concealment and pre-inspection procedures have been completed.

2. The concrete shelf and walkway have been erected and passed the inspection.

3. Cement, sand, stone and admixtures have been inspected to meet the requirements of relevant standards, and the concrete mix ratio notice has been issued for the test.

4. The electronic measuring instrument is accurate and flexible after inspection, and the vibrator (rod) is in normal operation after inspection.

Before pouring, the garbage, soil, oil stains and other debris on the steel bar should be cleaned up, and the cement mortar cushion block and plastic cushion block of the steel bar should be checked to see if they are padd. To make keys, if you use wooden formwork, you should water it to make the formwork moist. The sweeping port of the column formwork should be closed after removing debris and stagnant water.

1. When continuing to pour concrete at the construction joint, if the intermittent time exceeds the provisions, it will be treated according to the construction joint, and the concrete compressive strength is not less than when it is allowed to continue to perfusion.

2. Before continuing to pour concrete on the hardened concrete surface, remove the cement film on the surface and loosen the gravel or weak concrete layer, and fully moisten and rinse it, and remove the water remaining on the concrete surface. Before reinforcing it, it can be chiseled only after temporary support and reinforcement. The specifications and electrode types should conform to the design and construction specifications of the steel bar project, and there are material and product qualification certificates and physical property inspections.

3. Welders must hold the corresponding level of welder certificate before they are allowed to operate.

4. Before welding, two tensile specimens should be made with the same materials, welding conditions and parameters in advance, and the test results are greater than the tensile strength of the type of steel bar, and formal welding is allowed, and the specimens can not be sampled from the finished product at this time.

Legal basis: Regulations of the People's Republic of China on Information Disclosure

Article 7: All levels of the people** shall actively promote information disclosure efforts, gradually increasing the content of information disclosure.

Article 8: The people at all levels shall strengthen the standardization, standardization, and informatization management of information resources, strengthen the establishment of information disclosure platforms on the Internet, promote the integration of information disclosure platforms and government service platforms, and increase the level of information disclosure.

Article 9: Citizens, legal persons, and other organizations have the right to supervise administrative organs' information disclosure efforts, and to make criticisms and suggestions.

Legal analysis: The state issued the "China National Standard for Ready-Mixed Concrete", which came into effect on September 1, 2013.

Legal basis: "Law of the People's Republic of China on the Promotion of Circular Economy" Article 23 Architectural design, construction, construction and other units shall, in accordance with the relevant provisions and standards of the State, adopt energy-saving, water-saving, land-saving, material-saving technologies and small, light and renewable products for their design, construction and construction of buildings and structures. In areas where conditions permit, renewable energy sources such as solar, geothermal, and wind energy should be fully utilized.

The State encourages the use of non-toxic and harmless solid waste to produce building materials, encourages the use of bulk cement, and promotes the use of ready-mixed concrete and ready-mixed mortar.

It is forbidden to destroy cultivated land and burn bricks. It is forbidden to produce, sell and use clay bricks within the time limit and area specified by the people of provinces, autonomous regions and municipalities directly under the Central Government.

Regulations on the Quality Management of Construction Projects》 Article 29 The construction unit shall, in accordance with the engineering design requirements, construction technical standards and contract agreements, inspect the building materials, building accessories, equipment and commercial concrete, and the inspection shall have a written record and a special signature; If it has not been inspected or the inspection is unqualified, it shall not be used.