Construction method of the hottest pumping concret

2022-08-18
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Pumping concrete construction method

(I) concrete supply:

1. Commercial concrete: it is proposed to be produced by manufacturers that have passed ISO9002 quality certification. According to the actual situation of the project, the production technology monitoring requirements are as follows:

(1) material requirements:

a, bulk cement:

a. ordinary Portland cement or Portland cement above 325 is selected for cement

b. when cement enters the site, it shall have factory certificate or test report, and its variety, label and date of delivery shall be checked. If it is found that it is damp or expired before use, it should be sampled again for test

c. all quality indicators in the cement quality certificate shall comply with the provisions of the standard. Quality indicators include magnesium oxide content, sulfur trioxide content, loss on ignition, fineness, setting time, stability, compressive and flexural strength

d. the maximum cement consumption of concrete should not be greater than 550kg/m3

b, sand:

a. it is planned to give priority to the high-quality river sand of Shenzhen wharf

b. coarse and medium sand shall be preferred for concrete works. For pumped concrete, medium sand should be used, and the sand rate should be controlled at 40~50%

c. the silt content of sand (by weight) shall not be greater than 3% when the concrete strength grade is higher than or equal to C30; When it is lower than C30, it shall not be greater than 5%. For concrete sand with impermeability, frost resistance or other special requirements, its silt content shall not be greater than 3%. For concrete sand with C10 or below, its silt content can be relaxed as appropriate

c, stones (gravel or pebble)

a. granite is better for stones

b. the maximum particle size of stone shall not be greater than 1/4 of the structural section size, and shall not be greater than 3/4 of the minimum clear distance between reinforcement. The maximum particle size of concrete solid slab aggregate should not exceed 1/2 of the slab thickness. And shall not exceed 60mm. For pumped concrete, the ratio of the maximum particle size of gravel to the inner diameter of the delivery pipe should be less than or equal to 1:3, and the pebble should be less than or equal to 1:2.5

c. when the mud content (by weight) in the stone is equal to or higher than C30 concrete, it shall not be greater than 1%; Not more than 2% when it is lower than C30; For the concrete with frost resistance, impermeability or other special requirements, the silt content of the stone shall not be greater than 1%; For C10 or C10 concrete below the torsion, the silt content of stones can be relaxed as appropriate

d. the content of needle and flake particles in stones (by weight) shall not be greater than 15% when the concrete strength grade is higher or lower than C30; Not more than 25% when it is lower than C30; For C10 or below, it can be relaxed to 40%

d, water: drinking water that meets national standards can be used to mix all kinds of concrete without inspection

(2) operation conditions:

a. when issuing the task list, it must include the project name, location, location, quantity, various technical requirements for concrete (strength grade, retarding and special requirements), on-site construction method, production efficiency (or construction period), shift handover and overlapping requirements, as well as the coordination contents between the supplier and the demander, which must be issued together with the construction mix proportion notice

b. the test run of the equipment is normal, and the number of concrete transportation vehicles meets the requirements

c. the supply of materials is sufficient, especially the designated cement varieties have sufficient reserves or the subsequent supply is guaranteed

d. all materials shall pass the inspection and meet the use requirements

e. there is a reliable means of communication between the mixing plant, the pouring and tamping site and the transportation vehicles

(3) quality inspection requirements for commercial concrete:

a. when pumping concrete and supplying more than 100m3 of work per shift, quality inspectors should be sent to the site

b. before the concrete mixer truck leaves the station, each truck must be inspected by the quality inspector and the workability must be qualified before it can be released. Sampling inspection of slump once per vehicle; The unit weight of concrete vehicle shall be checked at least once a day for each mix proportion

c. during on-site sampling, the concrete from 1/4 to 3/4 after the unloading of the mixer truck shall be taken as a representative. Concrete sampling, specimen fabrication and curing shall be jointly signed and approved by both parties

d. segregation and initial setting shall not occur before unloading of mixer truck

2. Self mixed concrete production: self mixed concrete is used to prevent the temporary shortage of commercial concrete and the on-site mixing of sporadic concrete. The raw materials and mix proportion should be consistent with that of commercial concrete

(1) the amount of various materials in each plate (groove) determined according to the mix proportion should be weighed

(2) loading sequence: generally, stones are loaded first, then cement, and finally sand. If additives are needed, they should be added together with cement

(3) the shortest time of concrete mixing shall be determined according to the requirements of construction specifications. When admixtures are added, the mixing time shall be appropriately extended. The mixing time of fly ash concrete is 10 to 30s longer than that of the standard mixed soil

3. Concrete transportation:

(1) the means of concrete transportation on site include trolleys, buckets, chutes (Basement -), pumping, etc

(2) after the concrete is discharged from the mixer (2) successfully completing the task of canceling the floor bar, it should be transported to the pouring place in time, and the duration should not exceed the initial setting time. During transportation, concrete segregation, cement slurry loss, slump change and initial setting shall be prevented. If there is segregation when the concrete is transported to the pouring site, it must be mixed twice before pouring

(3) the concrete transportation road should be flat and smooth. If there is any unevenness, the bridge brace should be paved. During floor construction, a special bridge should be paved. It is strictly forbidden for trolleys and personnel to step on the reinforcement

(II) pumping concrete:

1. Pumping process:

(1) before pumping concrete, pump the clean water in the storage hopper out of the pipeline to wet and clean the pipeline, and then add cement mortar (or 1:2 cement mortar) with the same proportion as the concrete into the hopper, and start pumping concrete after lubricating the pipeline

(2) when starting pumping, the pumping speed should be slowed down, and the oil pressure change should be within the allowable range. Only when the pumping is smooth can the normal speed be used for pumping

(3) during pumping, the amount of concrete in the hopper should not be less than 10mm above the cylinder mouth to 150mm below the hopper mouth. Avoid low suction efficiency and easy to inhale air, resulting in frequent replacement of the plug, and too much will overflow and increase the load of the mixing shaft during reverse suction

(4) concrete pumping should be operated continuously. When the concrete supply is not timely, the pumping speed needs to be reduced. When the pumping is temporarily interrupted, the mixing should not be stopped. When the blade is stuck, it is necessary to reverse the queue, and then turn forward and reverse for a certain time. The pumping can continue only after the forward rotation is smooth

(5) in the middle of pumping, if the stopping time exceeds 20min and the pipeline is long, the pump should be started every 5min to pump a small amount of concrete. If the pipeline is short, the forward and reverse strokes of 2-3 can be used every 5min to make the concrete in the pipeline creep and prevent bleeding and segregation. If the pump is stopped for a long time (more than 45min), high temperature and small concrete slump may cause pipe plugging, Concrete should be removed from pumps and delivery pipes

(6) pump from far to near, and gradually remove the pipe during pouring

(7) when pumping in high temperature season, it is advisable to cover the pipe with warm straw bags for cooling to reduce the molding temperature

(8) the total horizontal conversion distance of the pumping pipeline should be less than the maximum pumping distance of the equipment

2. Cleaning work after pumping:

(1) when pumping is about to end, the amount of concrete stored in the concrete pipeline and hopper and the amount of concrete owed at the pouring and vibrating site should be estimated( Φ 150mm diameter pipe has 1.75m3 per 100), so as to determine the amount of mixed concrete

(2) when the pipeline is cleaned after pumping, use the air compressor to push the cleaning ball. First install the special cleaning water, then start the air compressor and pressurize gradually. During the cleaning process, the delivery pipe should be knocked at any time to know whether the concrete is close to emptying. When there is still about 10m of concrete in the delivery pipe, the compressor should be slowly decompressed to prevent large blasting and injury

(3) after pumping, the concrete pump, distributor and pipeline shall be cleaned immediately, and the pipelines shall be stacked according to different specifications after disassembly

(III) concrete pouring:

1. Preparation before concrete pouring:

(1) organize the construction team to carry out technical disclosure. The team must be familiar with the drawings and clarify the requirements of various technical factors at the construction site (concrete strength grade, impermeability grade, initial setting time, etc.)

(2) organize the team to carry out handover inspection of reinforcement and formwork. If the concrete construction conditions are not met, the concrete construction cannot be carried out

(3) organize construction equipment, tools and supplies to ensure good

(4) the formwork shall be watered before pouring, and the cleanouts of wall and column formwork shall be closed after removing sundries and ponding

2. General requirements for concrete pouring:

(1) the free fall height of concrete falling from the bucket mouth shall not exceed 2m, and measures must be taken if it exceeds 2m. Tumbling barrels, conduits, chutes or openings (openings) shall be used on the side of the formwork

(2) 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 reinforcement. Generally, the layering height is 1.25 times of the length of the acting part of the plug-in vibrator, and the maximum is not more than 500mm. The layer thickness of the plate vibrator is 200mm

(3) start the vibrator, hold the flexible shaft rubber hose at the upper end of the vibrator, and quickly insert it into the concrete. During vibration, the vibrator twitches slightly up and down, and the vibration time is 20~30 seconds, but it is subject to the fact that there are no bubbles on the concrete surface, no significant subsidence, surface bleeding and the formation of a horizontal surface. When using the plug-in vibrator, it should be inserted quickly and pulled out slowly. The insertion points should be evenly arranged, moved point by point, and carried out in sequence. There should be no omission, and it should be vibrated evenly. The moving distance shall not be greater than 1.5 times of the action radius of the vibrating rod (generally 300~400mm), and the distance close to the formwork shall not be less than 200mm. When vibrating the upper layer, it shall be inserted into the lower concrete surface by 50~100mm to eliminate the joint between the two layers. The moving distance of the plate vibrator shall ensure that the plate of the vibrator covers the edge of the vibrated part

(4) concrete pouring shall be carried out continuously. If the interval is necessary, the interval time should be shortened as far as possible, and the secondary layer of concrete should be poured before the initial setting of the previous layer of concrete. The maximum interval shall be determined according to all types of cement and initial setting conditions of concrete. Generally, more than 2 hours shall be treated as construction joints

(5) when pouring concrete, special personnel should be assigned to regularly observe whether the formwork reinforcement, reserved holes, embedded parts, dowel bars, etc. have displacement, deformation or blockage. If problems are found, they should be poured immediately and repaired before the initial setting of the poured concrete

(6) after pouring, check whether the reinforcement surface is polluted by concrete and scrub it in time

3. Wall concrete pouring:

(1) before wall pouring, or at the joint of newly burned concrete and lower concrete, 50mm thick cement mortar with the same proportion as the concrete shall be poured evenly on the bottom surface. Mortar shall be poured into the mold with a shovel, and shall be poured into the mold directly without a hopper

(2) the wall concrete shall be poured and vibrated in layers, and the pouring thickness of each layer shall be controlled at about 500mm. The concrete cutting points shall be distributed, circularly advanced and continuously carried out

(3) when pouring the wall opening, the concrete height on both sides of the opening should be roughly the same. The concrete shall be vibrated evenly and densely, especially in the parts with small wall thickness and dense reinforcement of door and window opening structure and staggered connection reinforcement Φ 25 vibrating rod, used for other wall beam parts Φ 50 vibrating rod, considering that it is impossible to directly

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