In summer, the temperature is high and the drying is fast
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The newly poured concrete may have the phenomenon of faster setting speed and lower strength
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At this time, the pouring, trimming and curing of concrete should be carried out with special care
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It is necessary to correctly analyze the causes of adverse factors, and then take effective technical measures to eliminate or minimize the adverse factors（ 1） When the temperature of concrete increases, in order to maintain the slump required by the pouring operation, the water consumption of concrete should be increased
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At the same time, with the increase of temperature, the slump loss speed of concrete mixture is accelerated
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The above situation makes the water consumption of concrete increase, and then leads to the increase of shrinkage and the decrease of strength
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Higher temperature will accelerate the setting of concrete, the transportation and finishing of concrete will become more difficult, and there may be more cold joints
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When the humidity is low or the wind speed is high, shrinkage cracks may appear more easily in the finishing process
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The early strength of concrete cured at higher temperature increases rapidly, but the strength that can be reached at 28 days will decrease accordingly
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Drying shrinkage will lead to more cracks, and the possibility of thermal cracking is also increased, especially for mass concrete
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In order to improve the pouring quality of concrete in hot climate, a detailed construction plan should be made and implemented
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Through careful selection of raw materials and construction methods, some adverse effects can also be reduced
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In addition, in each stage of concrete construction, measures should be taken to improve the construction quality in summer（ 2） When pouring concrete in hot weather, sufficient manpower, equipment and machines are required to deal with unexpected adverse conditions in time（ 1) The temperature of the concrete transported to the construction site can be detected, and the mixing plant can be required to adjust if necessary（ 2) During concrete construction in summer, the vibration equipment is easy to be damaged by heat, so standby vibrator should be prepared（ 3) All kinds of tools, equipment and materials in contact with concrete, such as pouring chute, conveyor, pump pipe, concrete pouring pipe, steel bar and trolley, shall not be directly exposed to sunlight, and shall be watered for cooling when necessary（ 4) The concrete pouring in summer should be carefully planned, and the concrete should be poured continuously and rapidly
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If there is bleeding on the concrete surface, it should be repaired in time（ 5) When it is found that the concrete has the possibility of plastic shrinkage cracking according to the specific climatic conditions, measures should be taken to control the water evaporation on the concrete surface, such as cooling the concrete, spraying water on the surface or taking windproof measures to reduce the surface evaporation speed（ Three) concrete maintenance (1) concrete maintenance function, such as hot weather, dry air, not timely maintenance, concrete moisture will evaporate too fast, form dehydration phenomenon, will make gel cement particles can not fully hydrated, can not be converted to stable crystallization, lack of enough cohesive force
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As a result, flake or powdery shedding will appear on the surface of concrete
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In addition, when the concrete does not have enough strength, the premature evaporation of water will produce large shrinkage deformation and dry shrinkage cracks, which will affect the durability and integrity of concrete
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Therefore, it is very important to maintain the concrete at the initial stage after pouring
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The concrete should be cured immediately after final setting, and the dry and hard concrete should be cured immediately after pouring（ 2) Curing method of concrete structure curing time (period) remarks: water storage curing of bearing platform and tie beam, water surface over the top of structure, continuous moisture curing for 14 days after final setting of concrete, immediately backfill column, pier body, plastic cloth or canvas and other moisture retaining materials after curing, continuously water wet curing, continuous moisture curing for 12 days after formwork removal, and the wrapping shall be intact, The inner surface shall be covered with condensation water bead, and the beam shall be covered with geotextile
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The concrete shall be continuously watered and cured for 14 days after final setting
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The indoor bottom plate and top plate of the surface course of the suspended casting block box shall be completely covered with geotextile
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The concrete shall be continuously watered and cured for 14 days after final setting
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For the parts that are difficult to be covered or cannot be covered, such as the roof of the box, etc, The top surface of precast box girder is completely covered with geotextile and continuously watered for curing
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After the final setting, the concrete is kept moist for 14 days
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After the formwork is removed, the web and head plate are continuously watered for curing
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(4) treatment measures for concrete pouring in summer
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(1) the final strength of concrete pouring in hot climate will be reduced, The influencing factors are as follows: 1; 2
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Condensation and early strength increase rapidly; 3
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The water consumption increases under the same slump requirement
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Treatment measures: 1
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Spray water on the aggregate pile to cool the aggregate by evaporation of water; 2
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Adding retarder in concrete; 3
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Replace part of mixing water with ice if necessary; 4
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Adding fly ash to adjust the influence of hot climate; 5
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Appropriately increase the amount of cement per cubic meter of concrete（ 2) The hot climate reduces the air content of concrete, which makes the concrete suffer some adverse effects
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It mainly includes: 1
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The durability of hardened concrete becomes worse; 2
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The workability of concrete mixture is reduced; 2
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The mixing amount is reduced
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Treatment measures: 1
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Frequently check the air content of concrete mixture; 2
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Increase the amount of air entraining agent（ 3) Due to the hot climate, the surface of newly poured concrete is dry, which leads to the following problems: 1; 2
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The weather resistance of concrete surface becomes worse; 3
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Cracks appear on the surface of concrete
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The treatment measures are as follows: 1; 2
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if it is necessary to spray water on the surface, the sprayer should be sprayed to avoid excessive surface watering
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3
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Maintenance shall be carried out immediately after finishing; 4
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Ensure that the slump is uniform and not greater than the specified limit（ 4) The hot climate leads to the uneven drying and setting of the concrete slab in the depth direction during the construction, thus forming the corrugated surface
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Treatment measures: 1; 2
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when this happens, spray a small amount of water with sprayer to extend the dressing time
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Source: Tencent.
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