Winter construction plan?

The following is the relevant content about the winter construction plan brought to you by Zhongda Consulting for your reference.

1. Winter construction preparations

1. When the average day and night temperature of the construction site (the average of the outdoor temperatures measured at 6, 14 and 21 o'clock every day) is lower than +5℃ or the lowest When the temperature is lower than -3℃, the concrete project shall be handled as winter construction.

2. In order to ensure the quality of project construction, construction will be carried out strictly in accordance with winter construction requirements from December 20 to March 10 of the following year.

3. Sign a service contract with the local meteorological department before starting construction, and keep abreast of meteorological trends and trends in weather forecasts to facilitate construction arrangements and make preventive preparations.

4. Based on the specific construction conditions of this project, determine the specific engineering projects or work content that require protection during winter construction, formulate corresponding protective measures for winter construction, and reserve and maintain materials and machinery. .

5. Strengthen maintenance of construction machinery in winter, frequently check and replace water-added, refueling and lubricating parts to prevent equipment from freezing and cracking.

6. Check whether employee housing and warehouses meet winter conditions, promptly construct winter awnings in accordance with winter construction protection measures, and prepare heating and fire equipment. When coal stoves and greenhouses are used for construction, measures must be taken to prevent fire and gas poisoning. There must be vents in the shed to ensure good ventilation, and various rescue equipment must be prepared.

7. Before entering winter, prepare the construction site for cold protection and heat preservation in advance, and take anti-slip measures for sidewalks, scaffolding springboards and workplaces.

2. Guarantee measures for winter construction of bridge and culvert projects

1. Bridge projects

The construction of all five bridges in our department has been completed, and the completion measurement work on the bridges has been completed . The erection work has not yet been carried out. Before winter comes, clean the gravel and accumulated water in the anchor holes, and cover the holes with rubberized sandbags to prevent rain and snow from entering the holes and freezing the concrete.

The prefabrication work of bridge sidewalk steps and brackets is carried out in a greenhouse.

After the bridge erecting machine has completed laying the bridge, it will be determined whether to install the brackets based on the weather and construction schedule. When installation and construction are required, anti-skid scaffolding must be used on the bridge. All construction personnel on the bridge must wear anti-skid boots and tie a safety rope before going on the bridge for construction.

2. Guarantee measures for winter construction of concrete projects

2.1. Before the concrete poured under winter conditions suffers from freezing, the critical frost resistance strength of concrete configured with ordinary Portland cement No less than 30% of the design mark. Concrete of C15 and below shall not be frozen until its compressive strength reaches 5Mpa. For concrete used under water-filled freeze-thaw conditions, the strength when it begins to freeze shall not be less than 70% of the design mark.

2.2. Concrete preparation, mixing and transportation for winter construction:

2.2.1. In order to reduce and prevent concrete freezing damage, use a smaller water-cement ratio and a lower slump. drop degree, in order to reduce the mixing water consumption, the cement grade can be appropriately increased at this time, and the cement grade should not be lower than P.O32.5. When concrete is mixed with antifreeze (admixture), its trial strength is one level higher than the design strength. It is prohibited to mix chlorine salt antifreeze in reinforced concrete to prevent chlorine salt from corroding the steel bars.

2.2.2. The mixing equipment should be treated with cold protection and set up in a greenhouse with a temperature not lower than 10℃. Wash the mixer drum with hot water before mixing concrete and after mixing. When mixing concrete, the temperature of the sand and gravel aggregate should be kept above 0°C, and the temperature of the mixing water should not be lower than 5°C. If necessary, heat the mixing water first. When the heated water cannot meet the mixing temperature, the aggregates can be heated evenly.

2.2.3. Determine the heating temperature that meets the needs of concrete pouring based on thermal calculation and actual trial mixing of water and aggregates.

2.2.4. The heating temperature of water should not be higher than 80℃. When the aggregate is not heated, the water can be heated to 80°C. Above, at this time, the aggregate and heated water should be put in first and mixed evenly, and then cement should be added to avoid direct contact between cement and hot water.

2.2.5. When the heated water cannot meet the requirements, the aggregates can be heated evenly, and the heating temperature should not be higher than 60°C. The rubble mixed with rubble concrete can be preheated.

2.2.6. Cement must not be heated directly. It can be transferred to a greenhouse for preheating before use.

2.2.7. Concrete should be quickly loaded and unloaded during transportation. It should not be transferred or blocked midway. During transportation, it should be covered with insulation to prevent cold.

When the slump of the mixed concrete decreases or rapid setting occurs, the heating temperature of the mixing embankment should be readjusted.

2.2.8. The concrete mixing time is about 50% longer than that of normal temperature construction. The mixing time of concrete mixed with admixtures should be 1.5 times of the normal temperature mixing time. The maximum allowable temperature when the concrete is discharged from the mixer is 40°C, and the mixing temperature of low-temperature early-strength concrete is not higher than 30°C.

2.2.9. The aggregates must not contain ice, snow, frozen blocks, or substances that are easily cracked by freezing. Strictly control the mix ratio and slump of the concrete, and the moisture brought by the aggregates and the admixture solution All moisture should be deducted from the mixing water.

2.2.10. When mixing concrete with admixtures, when the admixture is powder, it can be directly sprinkled on the cement in the required amount and added at the same time as the cement. When the admixture is a liquid, it should be prepared into a specified solution as required before use, and then according to the requirements of use, use a solution with a specified concentration to prepare a construction solution. Each solution should be placed in clearly marked containers and should not be mixed up.

2.2.11. When transporting concrete mixture during construction in winter, measures to minimize the heat loss of concrete mixture:

1) Correctly choose the location of the mixer and shorten the transportation distance as much as possible. Choose the best transportation route to shorten transportation time.

2) Correctly choose the form, size and insulation material of the shipping container. For long-distance transportation, concrete delivery trucks are used, and the capacity is selected according to the concrete construction volume and pouring time. When the distance is small, open transport trucks can be used, but they must be covered with insulation materials.

3) Minimize the number of loading and unloading and rationally organize loading, transportation and unloading of concrete.

2.3. Concrete pouring for winter construction:

2.3.1. Before concrete pouring, clean the ice, snow and dirt on the formwork and steel bars. When the ambient temperature is lower than -10℃ , use the greenhouse method to heat steel bars with a diameter greater than 25mm to positive temperature.

2.3.2. The pouring temperature of concrete should not be lower than 5℃ under any circumstances. The pouring temperature of thin-section concrete structures should not be lower than 10℃. The concrete should be poured in layers without interruption. , the thickness of each layer of pouring should not be greater than 20Cm, and mechanical tamping should be used.

2.3.3. Cleaning of new and old concrete construction joints:

1) The strength of the front layer of concrete shall not be less than 1.2Mpa.

2) The cement mortar, loose stones or weak concrete at the construction joints must be removed and rinsed with water, but there must be no accumulation of water.

3) Before pouring new concrete, it is advisable to lay a layer of cement mortar about 15mm thick at the transverse construction joints with the same cement mortar ratio as the concrete and a slightly smaller water-cement ratio. Then proceed to pour new layers of concrete. The new layer of concrete at the construction joints should be compacted.

4) When constructing joint concrete in winter, heat the joint surface before pouring new concrete so that the joint surface has a temperature above 5°C. After the pouring is completed, heat and maintain in time to keep the concrete joint surface at a positive temperature. , until the poured concrete obtains the specified frost resistance strength.

5) When the old concrete surface and exposed steel bars are exposed to cold air, the concrete within 1.5m of the new and old concrete construction joints and the exposed steel bars within 1.0m in length should be cold-proof and insulated.

6) The concrete is mechanically tamped and continuously poured in layers, with the thickness of the layers not less than 20cm.

2.4. Concrete maintenance for winter construction:

Concrete maintenance adopts the greenhouse method and the antifreeze method.

2.4.1. Maintenance by greenhouse method: This method is suitable for frame construction

1) Set up a greenhouse with steel pipes around the structure and wrap it with tape to seal it. The greenhouse must be firmly erected and It is airtight and covered with grass strips.

2) If a coal-fired heating furnace is used for heating, the exhaust pipe of the furnace must be led out of the shed to discharge the smoke outside the shed. To prevent gas poisoning and prevent excessive carbon oxide concentration from accelerating the carbonization of concrete.

3) The bottom temperature in the greenhouse should not be lower than 5℃. When it is lower than 5℃, a coal stove should be added. During the concrete curing period, special personnel will be arranged to inspect the coal furnace, add coal, and maintain the temperature in the shed.

4) There should be a certain humidity (measured by the laboratory) in the greenhouse. When the humidity is not enough, water should be sprinkled on the concrete surface and formwork or covered with moistening embankment bags.

2.4.2 Maintenance of concrete mixed with antifreeze:

1) The exposed surface of the concrete is covered with tape and straw bags, and watering and curing are not allowed under negative temperature conditions.

2) The temperature in the initial stage of concrete curing shall not be lower than the temperature specified by the antifreeze. When the specified temperature is not reached and the concrete strength is less than 3.5Mpa, insulation measures must be taken to ensure that the temperature of the concrete is not low. at the temperature specified by the antifreeze.

2.5. Concrete form removal

2.5.1. The concrete form removal strength in winter should meet the following requirements:

Meet the requirements for the form removal strength of concrete at normal temperatures. , and at the same time meet the requirements for anti-freeze

Concrete formwork strength at normal temperatures:

The side formwork has a concrete strength of more than 2.5Mpa, and its surface and edges are not affected by formwork removal. Only when it is damaged can the mold be removed.

The bottom formwork can only be removed when the strength of the concrete meets the following requirements.

2.5.2. The temperature difference between the concrete and the environment shall not be greater than 15℃. When the temperature difference is above 10℃ but below 15℃, cover the concrete surface immediately after removing the formwork, such as covering with straw bags. And colored tape.

2.5.3. For concrete cured by the greenhouse method, when the ambient temperature is still below 0℃ after the curing is completed, the formwork can only be removed after the concrete has cooled to below 5℃.

2.6. Inspection of concrete quality during winter construction

2.6.1. In addition to general concrete requirements, winter concrete quality inspection must also meet the following requirements.

2.6.2. During the mixing and pouring of concrete, measure the temperature of water and coarse and fine aggregate when they are loaded into the mixer, the mixing temperature of concrete, the pouring temperature and the ambient temperature. Test at least 4 times per work shift. When using low-temperature early-strengthening concrete or using thermal storage method to maintain concrete, testing should be carried out at any time within 3 days after pouring.

2.6.3. In addition to making standard maintenance specimens for winter construction concrete in accordance with regulations, construction inspection specimens are also made according to the needs of building maintenance, formwork removal and load bearing, so as to find out the strength. development. The maintenance of construction inspection specimens should be the same as that of buildings.

3. Guarantee measures for winter construction of masonry projects

The masonry projects in this pipe section are mainly roadbed reinforcement and ancillary projects and retaining wall projects after part of the frame is jacked into place. For construction sites that are scattered, small in volume, and do not affect the construction period, try not to schedule construction in winter. Construction sites with concentrated masonry and urgent construction schedules can be scheduled for winter construction.

3.1. Anti-freeze requirements for masonry projects:

The mortar shall not be allowed to freeze before its strength reaches 70% of the design strength.

The temperature during winter construction and the preparation before winter construction meet the aforementioned requirements.

3.2. Mortar configuration and masonry construction

Take the following measures to ensure that the mortar is at the correct temperature for masonry construction: heating mortar raw materials, mixing mortar in a greenhouse, adding salt, and mixing at the nearest work site Control, reduce accumulation, and avoid bad luck.

3.2.1. Heating of mortar raw materials; similar to heating of concrete raw materials, through thermal calculation, when using the greenhouse method, ensure that the mortar masonry temperature is not lower than 5℃.

3.2.2. The mortar is mechanically mixed in a warm shed, the ambient temperature is not lower than 5℃, and the mixing time is not less than 2 minutes. When the amount of mortar is small, it can be mixed manually in a greenhouse. It must be weighed and measured strictly according to the mix ratio. The number of mixing times is increased by 2-3 times compared with normal temperature.

3.2.3. The mortar can be mixed and used immediately. Do not transport the mortar in the middle. Try to use up the mortar within 30 minutes each time. When segregation or bleeding occurs during transportation or storage, the masonry Mix again before use. Mortar that has set or frozen must not be reused.

3.2.4. Warm sheds are set up at each work site, and are also used for masonry maintenance to ensure short-distance transportation of mortar (the distance is generally not more than 20m), which can avoid accumulation and no need to transport mortar.

3.2.5. Stones and sand used for masonry shall be cleared of ice, snow and frozen blocks in advance and transported into the shed in advance according to the progress of the project. The temperature difference between the stone surface and the mortar should not be higher than 20 degrees.

3.3. Masonry maintenance

The constructed masonry must be covered and maintained as the masonry is built. Under normal circumstances, straw bags and tape are used to maintain the concrete and masonry.

For conditional frame retaining walls, the greenhouse method can be used for maintenance, that is, the masonry construction is carried out in the greenhouse. Its construction is the same as the concrete greenhouse method.

In addition to making standard maintenance specimens for masonry construction in winter, construction inspection specimens are also made according to the needs of building maintenance, formwork removal and load bearing to find out the development of strength. The maintenance of test specimens should be the same as that of buildings.

4. Guarantee measures for winter construction of steel bar projects

Under negative temperature conditions, the mechanical properties of steel bars change, the yield point and tensile strength increase, and the elongation and impact toughness increase. Decrease, brittleness increases, and processing performance decreases.

4.1. Flash butt welding of steel bars in winter is performed indoors, and the ambient temperature during welding is not lower than 0°C.

4.2. The steel bars are transported into the processing shed in advance. The welded steel bars can only be transported outdoors after they are completely cooled.

4.3. Under difficult conditions, for steel bars that mainly bear static load, the ambient temperature of flash butt welding can be appropriately reduced to -10°C.

4.4. When arc welding in winter, take measures to prevent snow, wind, and heat preservation, and choose welding rods with better toughness. The joints after welding are strictly prohibited from coming into contact with ice and snow immediately.

4.5. When welding the help bars, five-point tack welding is used to fix the help bars and the main ribs. When welding the lap welds, two points are used for fixation. The tack welds should be more than 20mm away from the ends of the help bars or overlaps. The thickness of the steel bar and lap weld shall not be less than 0.3d and shall not be greater than 4mm, and the width of the weld shall not be less than 0.7d and shall not be less than 8mm.

3. Guarantee measures for winter construction of subgrade projects

The focus of low-temperature subgrade construction in winter is to handle the three links of soil antifreeze, soil excavation and earth filling.

1. Embankment filling construction

1.1. Definition of low temperature: the average day and night temperature is 0℃. Below and for 15 consecutive days, all construction should be handled as low temperature.

1.2. Embankments constructed at low temperatures must be treated before freezing. In addition to meeting the general construction regulations for roadbeds, the treatment methods must also clean up ice and snow, drain accumulated water, and use the same type of potholes as the foundation. Fill and compact the unfrozen soil. The treated foundation is immediately covered to prevent freezing.

1.3. Embankment filling

1.3.1. Filling requirements:

Materials for low-temperature embankment filling generally use Class A fillers. This section of the embankment is filled with Pebble soil (seepage soil) is used for construction.

1.3.2. Filling and compaction

Thickness of filling; winter subgrade construction shall be laid in layers according to the full width of the cross section, and the thickness of layered filling shall be based on the thickness of normal temperature construction Thinned by 20-25%, and shall not be laid in a diagonal layer. Construction shall not be interrupted until the soil layer has been compacted; the embankment shall be filled with 10-50cm of excess width on each side and compacted, and shall be trimmed off when the slope is trimmed after the winter. Tamp the excess part tightly.

Snow in the construction area must be cleared before construction.

When construction is stopped due to heavy snow or other reasons, the filling layer and slopes should be leveled and covered; before continuing construction, the edges should be cleared of ice and snow.

The filling embankment must be excavated, transported, filled and compacted at the same time. Construction shall not be interrupted before the laid soil layer is compacted. Ensure that the turnaround time of excavation, transportation, filling, and compaction is less than the freezing time of the soil.

The borrow pit should be continuously excavated to the design elevation at one time. Snow on the surface should be cleared before excavation. The exposed soil layers of the borrow pit and embankment slopes should be covered with straw bags.

The subgrade slope and side slope renovation work for low-temperature construction will be carried out after the freeze in the coming year.

2. Graded gravel project

2.1. Try to complete the graded gravel project before winter. The remaining amount should be constructed when the weather is above 0℃ and the wind is light. , no construction will be done on rainy or snowy days.

2.2. The gravel should be evenly graded, frozen aggregates should not be used, and the stone powder should be covered to prevent rain and snow from getting wet.

2.3. Stir the graded gravel and add enough water at one time according to the mix ratio to avoid sprinkling water at the construction site. Cover the cold-proof tent in time during shipment and transport it to the site as soon as possible.

2.4. After the mixed graded gravel is transported to the site, it should be paved and rolled immediately to avoid being exposed for a long time. Construction should not be interrupted before the paved layer is compacted.

2.5. After passing the rolling test, it should be covered with colored tape immediately and covered with straw bags for heat preservation and maintenance. At this time, no water should be sprayed for maintenance.

2.6. The mixing of graded gravel during construction must be matched according to the transportation and paving capabilities. It must be well connected so that it can be used when mixed, and the residence time and materials of the mixed graded gravel must be reduced. waste.

IV. Measures to prevent cold, antifreeze, fireproof and anti-slip mechanical equipment in winter:

1. Carry out comprehensive repairs and maintenance on all mechanical equipment before entering winter, and do a good job in oil and water management. Work, combined with the seasonal maintenance of mechanical equipment, promptly replace the lubricating oil of the corresponding brand; for mechanical equipment that uses antifreeze, ensure that the antifreeze meets local antifreeze requirements; for mechanical equipment that does not use antifreeze, appropriate antifreeze measures must be taken (discharge after shutdown) Cooling water or entering the greenhouse workshop)

2. The fuel used by various vehicles should be selected according to the ambient temperature. When starting a cold vehicle, it should first run at a low speed for a certain distance and then gradually increase the vehicle speed. .

3. Before starting the engine of a vehicle in winter, it is strictly forbidden to use an open flame to heat the existing fuel system to prevent fire.

4. When driving in ice and snow, the car must be equipped with anti-skid chains; the driver should check whether the vehicle's braking device is in good condition before getting out of the car. Do not get out of the car if it does not meet the requirements. In case of strong winds above level 6 , Stop operating in bad weather conditions such as heavy snow and fog.

5. Strictly implement the system of fixed machines and fixed personnel. Machinery custodians must stick to their posts, take good care of the equipment, and make corresponding records. Strictly implement the dispatch ticket system.

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