Key points and measures of quality and safety management in winter construction of building engineering

The Code for Winter Construction of Building Engineering stipulates that winter construction shall be started when the daily average outdoor temperature is steadily lower than 5℃ for five consecutive days. In winter, the temperature is low, the cold wave and snow are increasing, the construction conditions are unfavorable, the operator's movements are obviously slow, and the sensitivity is weakened, which is the season of frequent engineering quality problems and safety accidents. In particular, some construction projects face the node of construction period, and enterprises have a strong will to catch up with the construction period and schedule, which is prone to illegal phenomena.

Enhance quality awareness

Strictly grasp the quality management of winter construction

Pay more attention to winter construction, establish and improve the quality assurance system, fully implement the lifelong responsibility system for quality, and conscientiously implement various rules and regulations for winter construction.

? The construction unit shall, according to the project construction progress, determine the specific projects, quantity and content of winter construction, formulate a targeted and operable winter construction quality management plan, timely organize relevant on-site management personnel to conduct winter construction training, and improve the quality awareness of management personnel and operators. The construction unit shall formulate guidelines for winter construction management, inspect and guide the implementation of various winter construction measures, so as to nip in the bud and ensure the project quality.

? The content of the winter construction special plan compiled by the construction unit should be close to the engineering practice. Before construction, technical disclosure should be done well. The supervision unit should strictly review the special scheme, and the problems that cannot meet the requirements of winter construction should be solved with the relevant units such as design in time.

? Strictly control the quality of masonry engineering in winter and formulate anti-freezing protection measures. During construction, the temperature of mortar shall not be lower than 5℃, and construction shall not be allowed for projects without protective conditions. Wet operations such as energy-saving projects, roof waterproofing, exterior wall decoration and facing, indoor and outdoor plastering, floor tiles and coatings are not suitable for winter construction. Do a good job in the insulation and maintenance of temporary facilities and water supply pipes on the construction site, so as to provide reliable guarantee for winter construction.

? Pay close attention to the trend of meteorological changes, assign special personnel to collect and sort out meteorological data, adjust the project construction organization plan in time according to the actual construction situation, deal with severe weather such as snowstorm and frost in advance, resolutely put an end to the project quality problems caused by the sudden drop of temperature, and ensure the normal construction in winter. Avoid pouring concrete at low temperature. In principle, when the outdoor daily average temperature reaches below 5 degrees for 5 consecutive days, concrete operation shall not be carried out.

? All construction units should immediately conduct a comprehensive and detailed inspection of their winter construction projects, urge all construction sites to thoroughly implement the preparations for winter construction measures, and investigate all kinds of quality hidden dangers in advance. All supervision units should conscientiously perform their duties and strictly control the feasibility and implementation of winter construction quality measures. Engineering quality supervision institutions at all levels should strengthen inspections and severely punish those who fail to perform quality responsibilities and implement various winter construction quality management measures according to law.

Focus on the key points

Strengthen the safety management of the construction site.

In winter construction, according to the characteristics of different construction stages of the project, the winter construction safety measures are formulated to do a good job in winter production safety, especially at the end of the year and the beginning of the year. Strict management and inspection are needed to prevent all kinds of accidents. We should grasp the key points and earnestly do the following work:

? Construction enterprises should flexibly arrange different types of work according to climate change and make targeted safety technical disclosure. In case of severe weather such as strong wind, rain and snow, outdoor work should be stopped immediately, water and snow on the construction site should be removed in time, and effective measures should be taken to prevent slipping and falling.

? All kinds of scaffolding should be comprehensively inspected and reinforced, and the outer side of scaffolding must be protected in a standard three-dimensional way, and the vertical net and the flat net should be tight and firm. The roofs, floors and balconies under construction must be strictly protected, and high-rise buildings must be protected in three dimensions. Workers working high above the ground are not allowed to wear hard-soled high heels, and the clothes should fit neatly. In particular, personnel engaged in lifting operations must take anti-skid measures and fasten their seat belts.

? Prevent fire accidents. Each site should strictly control the fire source, strengthen the management of fire use, formulate fire prevention system, and improve the examination and approval system of fire use. Workers in welding, gas welding, painting and other industries. Special fire safety education should be carried out, the on-site fire fighting equipment must be complete, and the fire fighting road must be smooth. The construction area, office area and living area must be regularly inspected for fire control. Check whether there is a temporary fire truck passage in the construction area and whether it is unblocked; Second, whether to set up temporary fire water sources, install fire hydrants and equip them with hoses and guns when the building construction height exceeds 24 meters; Third, see whether the operators of electric welding and gas welding hold relevant certificates. Check whether the combustion performance grade of building components in office area and living area, temporary office building and dormitory reaches Grade A; Second, see if the staff dormitory is set separately from the construction work area; Third, see if there are illegal electricity consumption phenomena such as private wiring in the staff dormitory; Whether to use other metal wires instead of fuses, whether to use high-power electrical appliances, and whether to use open flames illegally.

? Prevent poisoning accidents. There are many kinds of antifreeze early strength agents used in winter construction, and most of these chemical additives are harmful to human body, especially sodium nitrite is similar to salt. Therefore, users must strengthen food safety education for employees and formulate strict transportation, storage, custody and collection systems for toxic substances such as sodium nitrite to prevent poisoning. It is forbidden to use charcoal, charcoal fire and other open flames for heating in the dormitory to prevent smoke poisoning and fire accidents.

? Prevent crane accidents such as tower cranes. Before the crane works in freezing rain, snow and freezing weather, it is necessary to assign a special person to strictly check the key parts such as insurance and limit devices to ensure the safety of the working machinery, and illegal operation and overload operation are strictly prohibited. It is necessary to increase the number of inspections and maintenance, and pay special attention to protecting the sensitivity and reliability of braking devices and safety devices to prevent mechanical accidents.

? Do a good job in emergency management. Each unit and project department shall establish a 24-hour duty system for special personnel and a shift-taking system for holiday leaders to ensure smooth information contact, timely grasp the situation of safety production, timely handle all kinds of unexpected accidents and major anomalies, and report to relevant departments at the first time.

The key points and measures of winter construction safety management and supervision of building projects are as follows:

Grasp the key points of winter construction

1 The winter construction period is roughly from June to February of the following year, and the requirements for heat preservation and safety measures are high and difficult.

Winter construction is faced with adverse weather factors such as low temperature, large temperature difference, wind, rain, snow, ice, etc., which is also a period of frequent accidents in various projects; At the same time, because of freezing, some hidden dangers of safety and quality began to be exposed after the weather turned warmer, which brought great difficulty to the prevention and disposal of accidents.

In winter, due to the special weather characteristics, there are many holidays, insufficient manpower, and many environmental protection bans, the time suitable for construction is very limited, and there are many safety accidents caused by rushing to the construction period.

In winter, due to the demand of heating and insulation, the use of fire and electricity increases, especially for the staff in living quarters, which is easy to ignore the safety of fire and electricity, so it is a high incidence period of fire accidents, so we must pay special attention to fire safety.

Make preparations.

1 The first thing to do is to make a good winter construction plan, plan scientifically, coordinate accurately and implement it to people.

2. Scientifically prepare the winter construction special plan. The key contents should include: construction procedure, construction method, site layout, supply plan of equipment, materials, energy and tools, safety and fire prevention measures, temperature measurement system and quality inspection system, etc.

3. Set up a special winter construction monitoring organization to track the weather changes in time, monitor the outdoor temperature and the temperature of mortar and concrete during construction in real time, compare them according to normal standards, and make correct decisions.

4 Conditional projects can be simulated in the construction of key parts, and then decide whether to carry out large-scale construction according to the experimental records.

Do a good job of self-management

Eat and drink well

Many people think that winter tonic means eating and drinking, which is wrong. Overeating and not paying attention to hygiene are often the reasons for frequent gastrointestinal diseases. Therefore, all on-site personnel must remember to eat at the designated dining place, and can't take supplements at will to prevent excessive heat generation. Of course, drinking to drive away the cold must also be moderate, and you must not be greedy; When sleeping, close the window cover and change clothes and bedding into winter ones. In addition, clothes must be aired, and bedding should be washed and aired frequently. If you can't avoid braved the snow or rain for construction or inspection, you must do a good job of protection and try not to be directly drenched in rain and snow to prevent colds, arthritis, rheumatism and other diseases. After working outdoors, you can take a hot bath if you can, and you can often soak your feet if you can't.

Do physical and mental health care well

There are many bad weather in winter, especially in the isolated construction site space, people's mood will also become melancholy, showing symptoms such as fatigue, irritability and easy to get angry.

Therefore, we must appropriately reduce the work pressure, do more exercise, participate in more group activities, and maintain a cheerful and upward mood.

Implement special construction measures.

Steel structure installation

1. Anti-skid measures must be taken when transporting and stacking steel structures, and attention should be paid to installing reinforcing chains. When stacking components of the same model, reasonable levelness should be ensured, and the shim should be on the same vertical line to prevent the components from slipping.

2. Before installation, the components shall be reinspected according to negative temperature conditions. If it is found that the deformation of the component is greater than the safety standard, it must be repaired and corrected on the ground before lifting and installation.

3, when there is snow, ice and dew on the component, it should be removed in time, and attention must be paid to prevent damage to the coating and structure during operation.

4, binding, lifting cable and hook pieces in direct contact, to add anti-slip pad. When lifting components directly with lifting rings and lifting lugs, check whether there is any damage to the connecting weld of lifting rings and lifting lugs. The connecting plate hoisted at the same time as the component, the ladder used by the installer, the fixture for calibration and the rope must be firmly bound.

5. When installing at negative temperature, the special machines and tools used shall be inspected according to relevant standards and requirements, and the operation can be continued only after passing the inspection; After the steel structure is installed, it should be corrected immediately and fixed permanently. The components installed on the same day should form a spatial stability system to ensure the installation quality and structural safety of steel structures.

6. When installing high-strength bolt joints, all sundries must be cleaned up, and those with freezing phenomenon should be melted and tilted clean. Before stud welding, parameters such as welding current and welding time should be measured according to the negative temperature value to ensure the welding quality of stud at negative temperature.

Reinforcement engineering

1, according to the winter changes, it is necessary to prepare special reinforcement work instructions in advance, organize reinforcement work learning, and avoid blind construction.

2. When the outdoor temperature is too low in winter, the steel bar processing shed should be closed for heat preservation to ensure that the steel bar does not bend to form straight threads at too low a temperature. Wind and rain protection measures should be taken for site binding.

3, reinforced in the process of transportation and processing should prevent the impact and abrasion, before use to ensure that the snow, frozen soil and other debris thoroughly clean up.

4, reinforced under the condition of negative temperature should strengthen the inspection, inspection, to ensure that there is no deformation, stress changes and other phenomena; Welding methods such as flash butt welding, arc welding and gas pressure welding should be adopted, and attention should be paid to prevent overheating, burns, cracks and other defects at any time.

5. Welded joints of steel bars shall be visually inspected by welders first, and then accepted by quality inspectors. If unqualified products are found, they should be reworked immediately; When the steel bar joint is used for connection, it can only be used after negative temperature test.

6. It is forbidden to carry out on-site welding in rainy and snowy weather. When welding is needed, effective shielding and protection measures should also be taken. Joints that are not cooled after welding should avoid encountering ice and snow.

template

Whether the external thermal insulation layer is attached to the formwork during winter construction and the thickness of thermal insulation layer are determined by thermal calculation. The removal time of formwork and thermal insulation is determined by calculating the maturity value of concrete and the same condition test block of pressure test concrete.

concrete work

1. Portland cement and ordinary silicon cement with high hydration heat are preferred for cement. The cement grade should not be lower than C42.5, the minimum cement dosage should not be less than 300kg/m3, and the water-cement ratio should not be greater than 0.6.

2. Aggregates required for mixing concrete shall be clean and shall not contain ice, snow, frozen blocks and other substances that are easy to freeze and crack. In concrete mixed with antifreeze containing potassium and sodium ions, active aggregate or materials mixed with these substances in aggregate shall not be used.

3. Admixtures mixed in concrete should be chlorine-free, which can effectively improve the technological properties of concrete, improve the durability of concrete, ensure its early strength at low temperature and hardening at negative temperature, and prevent early freezing.

4. In order to ensure the mixing temperature of concrete, the heating temperature of water must be strictly controlled. The water temperature should be controlled at 70-80℃ (not higher than 80℃). When mixing, aggregate should be added first, and then cement should be added to ensure that the outlet temperature is ≥ 15℃ and the inlet temperature is ≥ 10℃.

5. Before pouring concrete, remove the ice, snow and dirt on the formwork and steel bars, and preheat the formwork with a hot air blower: take wind-proof and antifreeze protection measures. Once the concrete is found to be frozen, it should be heated and stirred twice to make the mixture have suitable workability before pouring; When pouring, mechanical layered vibration should be adopted, the layered height should be strictly controlled, and the vibrating speed should be faster.

6, maintenance measures

1) When applied in winter, early strength water reducer or antifreeze is added to concrete. After concrete pouring, the comprehensive heat storage method is used for concrete curing, and a special person is responsible for temperature measurement.

2) During winter construction, the temperature shall be measured by designated personnel, and the mold entry temperature and curing temperature of concrete shall be monitored until the concrete reaches the critical strength of frost resistance.

7. Inspection of concrete quality in winter construction

1) Measure the heating temperature of water and the temperature when adding stirring.

2) Measure the temperature of concrete when it leaves the mixer and enters the mould, at least four times per shift.

3) Measurement method of concrete curing temperature

When thermal storage method is used for maintenance, the temperature measuring hole (point) should be set in the part that is easy to dissipate heat;

The measuring holes of the cast-in-place concrete beam slab are set perpendicular to the horizontal direction of the beam slab, and the measuring holes of the beam are set every 10m, and the hole depth is 1/3 of the beam height; Set a floor every 30m2 with hole depth 1/2 thickness.

4) Temperature measurement method: measure the temperature according to the number of the thermometer hole. After the thermometer is inserted into the thermometer hole, plug the hole, leave it in the hole for 3 ~ 5min, and then quickly take it out of the hole, so that the thermometer is flush with the line of sight, read it carefully and record it in the thermometer record. At the same time, cover the thermometer hole with thermal insulation material as it is.

5) Number all thermometer holes and draw the layout of thermometer holes.

6) Temperature control during concrete curing. The initial curing temperature of concrete shall not be lower than the specified temperature of antifreeze. When the specified temperature is not reached, the number of layers of heat shield should be increased immediately.

7. According to the specification, at least two groups of specimens with the same curing conditions should be retained at room temperature. One group is used to determine the strength of concrete before freezing, that is, the critical strength, and the other group is used to determine the 28d strength. The concrete specimen shall be made of the pouring structure mixture at the pouring site. Before the pressure test, the specimen should be parked indoors at normal temperature, and then the pressure test should be carried out after thawing. The parking time is 4- 12h.

8. Formwork and thermal insulation layer shall be removed after the concrete is cooled to 5℃. When the temperature difference between concrete and the outside is greater than 20℃, the concrete surface after formwork removal shall be temporarily covered to allow it to cool slowly. The formwork of load-bearing members shall be removed when the members meet the design and specification requirements.

Masonry engineering

1, before laying, the surface dirt, ice and snow, frost and other sundries of shale brick, lime-sand brick, aerated concrete, stone and other building materials should be removed. Masonry materials covered by rain and snow and frozen during storage shall not be used at will and must undergo strict inspection.

2. Materials such as lime paste, clay paste or electro-gypsum should be stored in heat preservation. In the case of freezing, they can only be used after thawing according to the thawing procedure.

3, masonry mortar should be not less than M2.5, important parts and structure should not be less than M5, appropriate USES ordinary portland cement mixing, winter masonry mortar without cement mixing shall not be used. Before using mortar admixture, it is necessary to master its chemical composition and properties in detail, and the dosage must be accurate.

Scaffolding engineering

1 Before construction in winter, all kinds of scaffolding used should be strictly and carefully inspected before entering the site to ensure that their configuration is safe, the foundation is solid and reliable, and stress concentration will not occur due to excessive deformation under temperature difference in winter. It is strictly forbidden to use products that have not been inspected and whose manufacturers are unknown.

2. When the wind cools down in winter and the rain and snow weather does not meet the construction conditions, construction is strictly prohibited, and personnel are strictly prohibited from entering and leaving the site at will; Before returning to work after rain and snow, it is necessary to clear the snow and sundries on the scaffold in time to reduce the extra load of the scaffold and avoid slipping accidents.

3. In windy weather, the connection between scaffold and structure should be strengthened in real time to improve its wind load resistance. When the weather gets warmer, it is necessary to check whether the scaffold foundation is stable in time, so as to avoid the scaffold sinking and tilting caused by soil thawing and causing accidents.

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