1, calculation method of starting and ending time of winter construction
"Winter is coming. If the average daily temperature is stable below +5℃ for five consecutive days, the first day of these five days is the first day of winter construction; When the temperature gets warmer, the average daily temperature in the last five days is above +5℃, so the last day of this five days is a whole day of winter construction. The temperature reaches below 0 C every day, which is also winter construction. "
2. Meteorological data of Zhengzhou City
According to the observation data of Zhengzhou Meteorological Bureau over the years, the time for Zhengzhou to enter winter construction is165438+1October 24th, and the termination time is March 5th of the following year, and the calendar day is 102d. The daily average minimum temperature is-1 1.4℃, the extreme minimum temperature is-17.9℃, the extreme minimum temperature is-12.5℃, and the average temperature during the period of daily average temperature ≤+5℃ is 1.6℃.
At present, the time has reached the end of 65438+2002 10. It is estimated that the construction can be started on February 6th, and the winter construction will end on March 5th. The construction time in winter is about 30 days. According to the current situation, this winter is warm, but in order to prevent sudden changes in the weather, we still need to make preparations for winter construction.
Third, the organizational measures for winter construction
1. The Engineering Department shall contact Zhengzhou Meteorological Department to release meteorological data in time; Receive the weather forecast in time and record it in the weather table to prevent the sudden attack of cold current.
2. Organize on-site management personnel to receive technical training for winter construction, learn relevant regulations and technical operation procedures for winter construction, and improve employees' awareness of winter construction.
3. Assign special personnel to measure outdoor temperature and mortar and concrete temperature during construction, and make records.
4, weekly production meeting, the main management personnel to participate in, timely discuss, study and solve the problems in winter construction.
6, material preparation
See the list of thermal insulation materials for winter construction.
7, the construction team to prepare
The quality inspector and foreman shall carry out safety education and technical disclosure in winter construction, and make corresponding records, which shall be signed by the construction team and submitted to the documenter and management department.
Three, the winter construction points and measures
1, temporary measures for production and life
1. 1 Office and meeting room are heated by electric heaters.
1.2 Use the standard curing room of the company's laboratory to cure the concrete test block.
2, reinforcement engineering winter construction guarantee measures
2. 1 steel bar will change its mechanical properties at negative temperature; The yield point and tensile strength increase, elongation and impact toughness decrease, and brittleness increases. This property is called cold brittleness. The aging, welded joints and surface defects of steel bars during processing will increase the cold brittleness of steel bars. Therefore, winter construction measures must be taken for reinforcement engineering.
2.2 Cold-drawn straightening of steel bars
Before cold-drawing and straightening steel bars, first check whether there are any serious defects such as traces and cracks on the surface of raw materials. If there are any, it is strictly prohibited. In winter, the cold-drawing straightening of steel bars should be strictly controlled, and the cold-drawing rate of first-class steel should not exceed 4%, and that of third-class steel should not exceed 1%.
2.3 negative temperature flash butt welding of steel bar
2.3. 1 negative temperature flash butt welding shall adopt flash-preheating-flash welding process.
2.3.2 negative temperature flash butt welding, the extension length increases by 10-20%, which is beneficial to increase the heating range, increase the heat reserve, reduce the cooling rate and improve the joint performance; The number of transformer stages should be reduced by 1-2 to ensure flashover; Before the flashover process begins, the steel bar should be contacted many times to increase the temperature of the steel bar, which is beneficial to the smooth progress of the flashover process and slow down the speed in the middle of the melting process. When preheating, the contact pressure is appropriately increased, and the preheating interval time is appropriately increased.
2.3.3 Welding parameters of negative temperature flash butt welding of steel bars are selected according to the following table.
Steel bar diameter
(mm)
Transformer series
Stretch length (mm)
Flash margin (mm)
Preheating allowance (mm)
Secondary flash allowance (mm)
Pre-forging allowance (mm)
See length of red area (mm)
12
V
30
10+e
five
20-25
14- 18
V
33
3+e
2-3
eight
5-6
25-30
20-25
Four, five
35
3+e
3-4
9- 10
5-6
25-30
28-32
Five, six
37
3+e
4-5
10
6-7
30-35
2.4 Negative temperature arc welding of reinforcement
2.4. 1 steel negative temperature arc welding must prevent overheating, burns, meat biting and cracks, and its structure should prevent the eccentric stress state at the joint. Welding parameters shall be selected according to the following table:
Welding type
Steel bar diameter (mm)
weld
number of plies
Horizontal welding
vertical position welding
Welding speed (mm/min)
Covered electrode diameter (mm)
Welding current (a)
Covered electrode diameter (mm)
Welding current (a)
Hem
10- 14
1
3.2
130- 140
3.2
90- 1 10
90- 100
4.0
150- 170
4.0
1 10- 130
16-20
2
3.2
130- 140
3.2
90- 1 10
80-90
4.0
150- 170
4.0
120- 140
22-40
three
4.0
150- 170
3.2
100- 120
70-90
5.0
180-240
4.0
140- 180
rhythm
18-20
1
3.2
140- 160
3.2
120- 130
22-40
2
3.2
140- 160
3.2
120- 130
4.0
160- 180
4.0
150- 170
2.4.2 In order to prevent the temperature gradient in the hot shadow area of the joint from suddenly increasing, when carrying out lap arc welding, the first layer of weld starts from the middle, and then the arc is brought to both ends; In vertical welding, the arc should be transported from the middle to the top, and then from the bottom to the middle. So that the steel bars at the end of the joint can achieve a certain preheating effect. In the future, when welding all layers of welds, the temperature should be controlled by layers for welding. The interlayer temperature is controlled between 150-350℃ to slow down the cooling.
2.4.3 In the multi-layer welding of negative temperature arc welding joint of Class II steel bar, the "tempering bead welding method" is adopted, that is, the length of the final tempering bead is shortened by 4-6mm at both ends of the previous bead, so as to eliminate or reduce the hardened structure and overheating area of the previous bead and improve the performance of the joint.
2.4.4 Reinforced joints shall be protected from rain and snow during welding, and shall be cleaned in time after rain and snow. It is forbidden to make the newly welded joint encounter rain and snow.
3, concrete engineering winter construction guarantee measures
If the newly poured concrete is frozen, the volume of mixed water will increase by about 9% after freezing, and the hydration of cement will also stop. After the normal temperature curing is resumed, the pores in the cement paste will obviously increase compared with the normal setting concrete, and the physical properties of the concrete will decrease. Therefore, in order to ensure the overall quality of concrete engineering, it is very necessary to prevent the freezing injury of concrete in the early stage of hardening in winter construction.
3. 1 concrete quality control
All commercial concrete is used in this project. Before 15d concrete pouring, the project technology department puts forward written technical requirements for concrete quality according to the actual engineering situation, design and construction specifications, and submits them to the commercial concrete manufacturers, who conduct tests according to the technical requirements and report the mixture ratio to the project technology department. After the approval of the chief engineer, the manufacturer of commercial concrete can produce concrete according to this mixture ratio, and produce it in strict accordance with this mixture ratio, which shall not be changed at will during the mixing process. If the site conditions change or raw materials change and it is necessary to change the mixture ratio, the changed mixture ratio can only be implemented after the approval of the chief engineer.
3.2 Control the mixing of commercial concrete. When pouring concrete, assign special personnel to the commercial concrete manufacturer to supervise the implementation of the mixture ratio, especially the dosage of additives such as antifreeze, which must be supervised by the manufacturer in strict accordance with the approved mixture ratio. If manufacturers are found to have cut corners, hell to pay will be punished.
3.3 In addition to the special requirements of the design and construction specifications (reflected in the technical requirements), what kind of additives and admixtures are used for concrete shall be determined by the Project Technology Department in principle, submitted to the project supervision company and customers for approval, and implemented by the commercial concrete suppliers.
3.4 On-site acceptance of commercial concrete, on-site quality inspection and testing personnel should check the quality of concrete in strict accordance with technical requirements, and the acceptance of concrete should be tested by sampling from the pouring site, especially the slump. Manufacturers of commercial concrete must consider the comprehensive factors such as transportation distance, pouring speed and climate to determine the slump when leaving the factory.
3.5 When pouring concrete, the tester shall make test blocks as required, and the number of test blocks shall be two groups more than usual. These two groups of specimens should be cured under the same conditions as the structure to test the strength of concrete before freezing and after curing at room temperature for 28 days.
3.5. 1 concrete pouring
Before concrete pouring, if there is snow or dirt on the formwork and reinforcement, it must be removed before concrete pouring. When the pouring temperature is required to be not lower than 5℃, the pouring speed and pouring temperature should be determined by calculation when the mass concrete of the foundation slab is poured in layers, so that the concrete temperature of the poured layer is not lower than the calculated temperature or lower than 2℃ before it is covered by the previous layer.
Maintenance of concrete
Concrete curing mainly adopts comprehensive heat storage method, and antifreeze is added to concrete. After pouring, cover it with straw bag (sack) and plastic film in time for maintenance. Maintenance under negative temperature, concrete surface watering is strictly prohibited. For the curing of mass concrete of foundation slab, see the construction scheme of mass concrete.
Temperature measurement of concrete
For the temperature measurement of mass concrete, please refer to the construction scheme of foundation engineering for the mercury thermometer, temperature measurement method and arrangement of temperature measurement points.
3.6 concrete quality assurance system
3.6. 1 Establish a perfect organizational system, with managers performing their duties and management in place. And formulate the corresponding reward and punishment system, and the management department will determine the reward and punishment scale.
3.6.2 Full-time personnel shall be responsible for formwork, concrete pouring and test, with one person for each item below 0.000. The quality inspector and the safety officer are also divided into classes to ensure the construction period and quality of concrete.
3.6.3 All measurement and inspection results shall be filled in "Winter Construction Record of Concrete Engineering" and "Winter Construction Daily of Concrete", and the format is shown in the attached table.
4. Technical measures for winter construction of plastering project
4. 1 According to the construction progress, only late plastering will be carried out in winter.
4.2 The hot water for mixing mortar shall be heated by electric heating tube, and the water temperature shall not exceed 80℃, and the water temperature shall be adjusted according to the requirement that the mortar temperature shall not be lower than 5℃ during masonry.
4.3 The matters needing attention in the mixing and transportation of plastering mortar are the same as the above-mentioned masonry mortar. Mortar should be used at a temperature above 5℃.
4.4 It is forbidden to use frozen mortar or mix it with hot water for reuse.
4.5 Mortar shall be used as it is mixed, and shall not be piled up and transported for the second time. Mortar storage time shall not exceed 20min.
5. Winter construction measures of underground waterproof engineering. Waterproofing should be carried out in sunny days with high temperature. When the temperature is lower than 5℃, the greenhouse should take warm-keeping measures. See the underground waterproof construction scheme for details.
Fourth, safety and fire prevention measures
1, safety assurance measures
1. 1 The anti-skid measures of this project adopt cement pavement, and the main construction areas are all hardened. After the heavy snow, the full-time foreman is responsible for clearing the snow in time.
1.2 On-site construction personnel shall abide by the dress code, and shall not wear coats that are easy to scratch and fall off and shoes that are easy to climb and slip.
1.3 power switch, control box and other facilities should be locked, and designated persons should be responsible for management to prevent electric leakage and electric shock accidents.
1.4 safety personnel should strictly check the field work.
2. Fire prevention guarantee measures
2. 1 It is forbidden to use electric and coal stoves for heating indoors and outdoors.
Smoking is strictly prohibited in the non-smoking area.
2.2 If additives such as sodium nitrite need to be added, the external flow should be strictly controlled and marked on site to prevent people from being poisoned by eating by mistake. (This project is not stored in principle, unless it is purchased temporarily due to special needs).
2.3 The personnel who use naked flame on site, such as workers engaged in gas welding, electric welding and gas cutting, must have a work permit, and the site must have a hot work permit issued by the security department before construction is allowed.
2.4 Flammable and explosive materials should be stacked independently and marked, away from fire sources.
2.5 to carry out safety construction competition, regular inspection. Every day, the safety officer will list the irregular operation orders on the blackboard and criticize them. If the circumstances are serious, they will be severely punished until they are handed over to the judicial department for handling. Do a month-end appraisal once a month to give certain material rewards to civilized construction teams and individuals.
List of thermal insulation materials for winter construction
name
unit
amount
comment
straw bag/sack
individual
3000
0.5× 1 m2
plastic membrane
The second part of money supply
1400
electric radiator
individual
eight
sodium chloride
kilogram
According to actual needs
Temperature measuring wires and contacts
root
30 pieces
Temperature detector
platform
2
thermometer
individual
10