Technical quality control of cast-in-place concrete in main building project?

At present, concrete is used more and more widely, and its quality directly affects the safety of the whole building structure. Although there are mature theories about concrete production, there are often some problems in construction, which requires us to strictly control all construction links in construction. According to various specifications and what we have seen and heard in the work, some understandings of concrete pouring are put forward.

1. Construction preparation

1. 1 Make a written safety technical disclosure to the workers before concrete pouring. Disclosure should be clear about the problems that should be paid attention to in the construction process, which is targeted and operable. Before concrete pouring, oral disclosure must be made to the team, focusing on controlling the concrete label, vibrating spacing and vibrating time of columns, beams, beams and slabs and shear walls.

1.2 prepare machinery and equipment such as hoppers, rollers and vibrators, and have spare vibrators. Before pouring, the machines and tools used should be inspected and debugged, and full-time technicians should be equipped for maintenance at any time.

1.3 in the concrete construction stage, we should grasp the weather changes and cover it with plastic film concrete when it rains, so as to ensure the smooth and continuous pouring of concrete and the quality of concrete. According to the engineering needs and seasonal construction characteristics, prepare the materials necessary for rain and heatstroke prevention during pouring.

1.4 Before pouring concrete, check and control the size, specification, quantity and position of formwork, reinforcement, protective layer and embedded parts, and the deviation value shall conform to the current national quality acceptance evaluation standard. In addition, the stability of formwork support and the tightness of formwork joints should be checked. Template, steel bar should be checked and concealed after acceptance meets the requirements, before pouring.

2. Safety measures

2. 1 General requirements

2. 1.65438+ It is considered illegal to wear a helmet without a forehead belt. According to the structure, cover the safety net completely before pouring.

2. 1.2 When pouring beam-column concrete, aerial workers who cannot use reliable protective facilities must wear safety belts. Seat belts should be hung high and used low, not hung high and used low. During operation, swing collision should be prevented to avoid accidents.

2. 1.3 All construction personnel must receive education on construction safety and production, and can only work at their posts after passing the examination. Those who have not received the education of construction safety production or failed the examination are not allowed to work at their posts.

2. 1.4 vibrator operators must wear insulating gloves and shoes.

2.2 Safety requirements for pumping

2.2. 1 The concrete pump must be operated by a trained and qualified professional driver who is the person in charge of the whole equipment. Non-driver operation is strictly prohibited.

2.2.2 Safety protection devices, such as warning signals, gratings, protective covers, etc. , must be placed in an obvious position, and shall not be removed or replaced with other things.

2.2.3 The legs must be locked in place by mechanical means or hydraulic means, and the pump body must be kept horizontal. If it is not normal, you must adjust your legs to level.

2.2.4 The installation of conveying pipes (especially risers) must be firm and reliable, and all conveying pipes shall not be deformed such as expansion, contraction and distortion after installation. The installation position shall be convenient for people to approach, and the bolts shall be tightened. When pipelines are laid along the ground, pads (such as logs) should be added to facilitate the assembly and disassembly of pipeline joints. The pipe joint must be tightened.

2.2.5 The voltage and capacity of power supply must meet the specified requirements.

2.2.6 In order to prevent air from being inhaled, the concrete in the hopper must be equipped with at least a stirring suction pipe, otherwise the air will be pumped back to the concrete and impact the hopper, causing unnecessary damage and accidents.

2.2.7 During the operation of the pump, do not extend your hand to the reversing valve, mixer or other moving parts.

2.2.8 Troubleshooting, repair and maintenance can only be carried out when the power supply is cut off.

2.2.9 The conveying pipeline cannot be disassembled under pressure. Before dismantling the pipeline, concrete must be pumped out, and there should be no pressure in the pipeline.

2.2. 10 when the pump body is completed or stops working for some reason, the pump body and pipeline must be washed clean to avoid concrete bonding affecting the use.

3. Construction process

3. 1 Precautions during pouring:

3. 1. 1 In the pouring process of commercial concrete, concrete should not be distributed centrally to prevent accumulation or insufficient vibration. Concrete should be poured continuously from far and near layers, with vertical structure first and horizontal structure later, and the thickness of protective layer of steel bars should be ensured. In the pouring process, the uniformity and compactness of concrete should be controlled. After the concrete mixture is transported to the pouring place, it should be poured into the mold immediately. In the process of pouring, if it is found that the uniformity and consistency of concrete mixture have changed greatly, it should be handled in time.

3. 1.2 When pouring concrete for columns and shear walls, attention should be paid to prevent concrete from delamination and segregation. When concrete is discharged from the hopper for pouring, its free-falling height should generally not exceed 2M, and the height of pouring concrete in the vertical structure should not exceed 3M. Therefore, string drums, chutes and chutes should be used for blanking during pouring.

3. 1.3 When pouring concrete, observe whether there is any abnormality in formwork, support and scaffold at any time. When looseness or deformation is found, stop pouring immediately, reinforce immediately, and continue pouring concrete after finishing.

3. 1.4 when pouring concrete, it is found that the reinforced cushion block moves, and the thickness of the reinforced protective layer cannot be guaranteed, or the reserved hole is displaced, and concrete can be poured only after immediate rectification.

3. 1.5 once the concrete pouring is completed, the beam slab concrete should be continuously poured as soon as possible after the column and wall pouring is completed.

3. 1.6 When pouring concrete, when the pump blocks and removes the pipeline, a template or sack should be laid on the head of the pump pipe before removing the pipeline, and the concrete poured from the pump pipe should be caught by the template or sack, and then the concrete should be transported to the place where it is being poured. If concrete is accidentally left on the floor, it should be cleaned immediately. Before pouring, clean up the 1 1 layer of redundant steel pipe fasteners, so as not to be buried with the remaining concrete.

3.2 vibrator operation:

3.2. 1 When pouring beam concrete, there are two vibrating methods of internal vibrator, one is vertical vibrating, that is, the vibrator is perpendicular to the concrete surface; The other is oblique vibration, that is, the vibrator forms a certain angle with the concrete surface, about 40o~45o.

3.2.2 The operation of vibrator should be "fast plug and slow pull". The purpose of rapid insertion is to prevent the surface concrete from being vibrated first, and then delaminated and separated from the concrete below; Slow pulling is to make concrete fill the hole caused by the withdrawal of vibrator. During the vibrating process, the vibrator should twitch slightly up and down to make it vibrate evenly up and down.

3.2.3 When the concrete of columns and beams is poured in layers, the upper concrete should be inserted into the lower concrete about 5 cm when vibrating, so as to eliminate the joint between the two layers of concrete. At the same time, when the upper concrete is vibrated, it should be carried out before the initial setting of the lower concrete.

3.2.4 Each insertion point should master the vibrating time. If it is too short, it is not easy to tamp; If it is too long, it may cause concrete segregation. Generally speaking, the vibration time of each point should not be less than 10s. However, it should be considered that the concrete surface is horizontal, no longer sinks obviously, no bubbles appear, and the surface is covered with mortar.

3.2.5 The insertion points of vibrators shall be evenly arranged, and can be moved in the order of "determinant" or "staggered", and shall not be mixed to avoid confusion and vibration leakage. The distance of each vibration position should not be greater than 65438+ 0.5 times of the action radius r of the vibrator. Generally, the action radius of vibrator is 30 ~ 40 cm.

3.3 Specific pouring parts should be paid attention to:

3.3. 1 When the concrete grade of the column exceeds that of the beam, appropriate measures can be taken to ensure that the quality meets the design requirements.

3.3.2 When pouring beam-slab concrete, if initial setting of construction joints occurs, the cement film and weak concrete layer on the surface shall be chiseled before pouring beam-slab concrete, and garbage shall be removed and washed with water, but no water shall be accumulated. Before pouring beam-slab concrete, it is advisable to spread a layer of cement mortar with the thickness of 10 ~ 15 mm on the surface of construction joints, and its mixture ratio is the same as that of concrete.

3.3.3 In the process of concrete pouring, it is necessary to ensure the correctness of the position of concrete protective layer and reinforcement, and the reinforcement shall not be trampled (scaffolding shall be laid first), and the original positions of embedded pipes and reserved holes shall not be moved. If deviations and displacements are found, they should be corrected in time.

3.3.4 When pouring concrete at the intersection of column beam and primary and secondary beams, the reinforcement is generally dense, especially the upper negative reinforcement is thick and numerous. Therefore, it is necessary to prevent concrete from being difficult to cut, and pay attention to mortar blocking stones. If necessary, this part can be poured with fine stone concrete.

3.3.5 When pouring concrete for the core tube, in order to avoid the slab and stair concrete flowing into the wall, the shear wall concrete should be poured to the bottom of the slab first, and then the slab beam concrete. The position where the wall meets the stairs is intercepted by the steel wire mesh. When the wall concrete begins to set initially, the stair concrete is poured directly without dismantling. When pouring concrete, don't move the steel bar at will, and often strengthen the inspection of the thickness of the protective layer of the steel bar. The negative reinforcement of the pedal should be adjusted in time. After pouring, rub it twice with a wooden trowel to prevent cracks on the concrete surface. The test block cured under the same conditions shall prevail, and the next working procedure can be carried out only after it reaches 1.2Mpa.

3.3.6 For the frame beam-slab structure, after concrete pouring, the beam surface should be flattened with adhesive tape to avoid uneven beam surface after formwork removal.

4. Concrete curing

4. After1pouring 12h, it shall be watered and maintained by special personnel, and the number of times of watering every day shall ensure that the surface of concrete members is kept moist for not less than 7 days.

4.2 After the strength of poured concrete reaches 1.2N/m㎡, pedestrians, templates and supports shall not be installed on it.

4.3 The concrete that has entered the formwork shall be covered in time to prevent sudden rain and rain.

5. Matters needing attention in form removal:

5. 1 When the non-bearing formwork on the side of reinforced concrete structure is removed, the concrete should have sufficient strength.

5.2 Don't use too much force or too fast when ripping, pay attention to protect the edges and corners, and it is forbidden for the template to hit the edges and corners when lifting.

5.3 According to the test results of test blocks, correctly grasp the time of form removal to prevent premature form removal.

5.4 Strengthen the protection of finished products. For the concrete external angle of the crowded and material conveying channel, angle steel and other external angles shall be used for protection after formwork removal to avoid collision.

6. Conclusion

To sum up, there are many factors affecting the quality of concrete pouring, which requires our engineers and technicians to grasp the key points, control the quality, formulate effective construction methods, do a good job in technical disclosure, strengthen on-site management, and implement the responsibility to people, so as to gradually improve the quality of concrete pouring and strive to comprehensively improve the quality of engineering construction.

This paper introduces the content of "technical quality control of cast-in-place concrete for main building projects". Welcome to Zhong Da for more information.

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