In case of heavy rain, the construction joint shall be reserved on the beam near the pouring part immediately, and it is best to leave the construction joint in the middle of the beam height
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In July this year, we sent three trucks of concrete to a construction site
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Finally, we used an excavator to drag the transport vehicle out of the muddy area
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Soon after the transport vehicle arrived at the construction site, it rained heavily and the vehicle fell into the mud
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4、 When pouring beams and slabs in light rainy days, the “four at any time” shall be achieved, that is, pouring at any time, vibrating at any time, rubbing at any time, and covering with plastic film at any time
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As defined in astm403, the test results of cement mortar with cement sand ratio of 1:2 show that the initial setting time is shortened by half when the temperature is increased from 28 ℃ to 46 ℃
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The concrete is not prone to plastic shrinkage cracks, which can play a favorable role in the quality of the concrete within a certain rainfall range
. Fixing Socket Angular End Nail Plate
If it rains frequently, what should be done for concrete construction? Before the exchange and discussion, let’s look at a typical problem case ☟ when pouring the floor slab of a residential project, the freshly poured concrete on site was not covered due to heavy rain, resulting in serious slurry flow and sand on the concrete surface【 Consequences of the problem] ① serious slurry flow caused by heavy rain scouring the concrete surface is equivalent to reducing the effective thickness of the floor ② After the rain, water leakage and other phenomena are found in some floors ③ Affect the strength of concrete ④ Poor surface appearance [remedy] ① use high-grade cement mortar for on-site supplementary polishing immediately after the rain stops ② Flaw detection test shall be conducted for this part of concrete to confirm whether the concrete strength of this layer meets the requirements ③ If the concrete strength cannot meet the requirements, the designer shall be requested to take reinforcement measures for this floor [lessons from the problem] the quality awareness of the project management is weak, the on-site personnel do not understand the weather conditions of the day before pouring concrete, and do not arrange personnel to cover this part of concrete in time when it rains
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For example, if the following problems are not solved well, the construction quality will be a problem: in the rainy season, the moisture content of some raw materials of concrete changes greatly
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After the rain stopped, the concrete had been delivered for more than 8h, and all the concrete was scrapped
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In order to solve these problems and prevent these troubles, the following suggestions are put forward for colleagues’ reference: first, for the mixing plant where sand and gravel are stored in the open air, when it rains, Two points shall be done: (1) the loader driver shall shovel more than 20cm from the ground when loading to prevent ponding on the ground and sand and gravel with excessive water content from shovel into the bucket（ 2) The production operator shall pay attention to observing the mixing current of the concrete mixture when it is about to leave the machine
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When the hourly evaporation rate of concrete is greater than 1.0kg/m2, plastic cracks are easy to appear, and are more obvious in dry conditions
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It often encounters showers or rainstorms
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How can concrete production enterprises control the water consumption in actual concrete production to be consistent with that in mix proportion design? In some areas, the rainy season is usually long
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2、 For the construction site without hardened construction road or even subgrade paved with slag, the supply shall be refused during the period of rain forecast
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After the concrete without final setting is soaked in rainwater, a weak layer of 5 ~ 10mm will be generated on the concrete surface, which will affect the overall quality of concrete
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The rainy season does bring a lot of trouble to concrete pouring
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Our company once had a car sinking accident
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When the outgoing current of the continuously produced concrete mixture obviously decreases, the water shall be manually reduced by 5 ~ 10 kg / M immediately ³。 If the rain continues to fall heavily and production is needed, continue to reduce water according to the above methods, and the production water consumption can reach 60 kg / m at the most ³。 However, the same amount of sand should be added while reducing water, otherwise the square will be lost
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two Zhao Hengshu (Shandong Yichen Concrete Co., Ltd., senior engineer) will bring many problems and troubles to ready mixed concrete enterprises due to rainy summer
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three Zhang Wei (senior engineer and doctor of engineering of Nanjing Shenhe New Material Technology Co., Ltd.) in rainy season, the moisture content of some raw materials of concrete changes greatly, especially the fluctuation of moisture content of materials in open quarry, which brings trouble to the correction of material measurement in the central control room of commercial mixing station, but this problem can be overcome, It’s just that the efficiency of production and departure will be slightly reduced
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Controlling the factory’s design slump is to control the theoretical water consumption in the concrete mix proportion
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5、 When pouring concrete components for foundation works or low-lying parts in rainy season, drainage ditches must be dug around the foundation or components to drain the rainwater in time to prevent the rainwater from soaking the newly poured concrete
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Therefore, we should take warning and take precautions
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The increase of temperature of fresh concrete results in accelerated slump loss, rapid hydration reaction and accelerated concrete setting, which is unfavorable to the development of long-term strength
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The central control room shall have laboratory quality inspectors to monitor the workability and slump of the delivered concrete to ensure the quality of the delivered concrete.
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3、 In case of heavy rain during pump truck construction, the pumping operation shall be suspended, the boom shall be turned to the opposite direction of the building, the height of the boom shall be reduced, and the extension radius of the boom shall be reduced (that is, the overturning moment of the boom shall be minimized)
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In case of sudden rainstorm during concrete construction and its duration is long, the touched concrete shall be covered immediately, and the re pouring time shall be less than the initial setting time of concrete
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Using concrete under hot and high temperature conditions will shorten the setting time of concrete
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The water consumption of concrete produced under high temperature conditions will increase to meet the construction needs of concrete
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The construction unit shall follow the specification requirements for covering and maintenance after concrete pouring, which has a good effect on concrete maintenance
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When the glue slurry on the concrete surface is washed away and the concrete sand particles are obviously exposed on the surface, cement paste, mortar or polymer cement mortar can be paved on the surface to enhance the strength and protective layer of the concrete surface
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Pay attention to observe whether the two supporting feet near one side of the building sink and whether the foundation pit slope near the supporting leg collapses
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The concrete central control room can calculate the concrete mix proportion in actual production according to the fluctuation of the average moisture content of sand and gravel
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Because the factory’s concrete mix proportion has a one-to-one correspondence between its slump and theoretical water consumption when other conditions remain unchanged
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In case of the above phenomena, the pump truck shall be started immediately to prevent the pump truck from rollover
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The rainwater provides water to the concrete surface, reduces the temperature of the concrete, alleviates the setting time, and the concrete is cured by rainwater
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If a certain amount of rainfall is encountered during construction, it will not affect the internal quality of the poured concrete
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What can be done to prevent these problems? We might as well listen to the discussion of industry experts and front-line personnel ▼ this article “special planning: related problems of concrete construction in rainy season” is published in commercial concrete one Wu Qingjia (chief engineer of Kunshan Hongji Concrete Co., Ltd.) pouring concrete in hot weather in summer is not a rare construction process
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When the initial setting time has passed when pouring again, the treatment method is that the construction joints of beams, plates and other parts shall meet the provisions of the design and gb5024 code for construction and acceptance of concrete structures
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What should be paid attention to in concrete construction and maintenance? If there is sudden rainfall during construction and it is too late to adopt relevant measures, what quality problems will occur in concrete? In case of quality problems, what remedial measures are available? The concrete construction in rainy season will affect the structural quality
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A mixer truck is generally 6 ~ 10m ³ For concrete, if the slump of the previous plate is too small, the next plate can be enlarged; The slump of the last batch of concrete is too large, and the next batch can be reduced
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However, if there is ponding on the surface of the poured area, try to drain it, because the ponding on the surface will affect the strength and carbonation performance of the concrete surface
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