The length of the construction period is very important for a construction project. With the extension of the construction period, the personnel salary, mechanical equipment cost, material cost and management cost increase, which is not conducive to the construction management of the construction unit. In many cases, even in winter, it is inevitable to carry out winter construction because of the progress needs and cost accounting of construction projects. According to JGGJ104-97 Code for Winter Construction of Building Engineering, when the daily average outdoor temperature is stable below 5℃ for five consecutive days, winter construction should be carried out and corresponding protective measures should be taken. If the corresponding measures are not taken or taken improperly, it will bring hidden dangers to the project quality and easily lead to quality accidents. For concrete construction, which is widely used in the construction process, it is greatly influenced by temperature change. In the process of concrete construction, the increase of its strength mainly depends on the hydration of cement in concrete at room temperature. If the temperature is too low, the volume of water will expand after freezing, which will destroy the concrete structure, affect the engineering quality and bring hidden dangers to the engineering safety. Therefore, when the room temperature is lower than 5℃ required by the specification, corresponding thermal insulation measures and winter construction techniques should be taken.
1 winter construction preparation
1. 1 Data collection before winter application
First of all, it is necessary to collect the winter meteorological data of the project area in recent 3 ~ 5 years, understand the local climate characteristics, temperature changes, historical lowest temperature, maximum value of snow and ice and duration, take preventive measures against the weather changes and rain and snow weather in the coming week, maintain good communication with the meteorological station, and be alert to the sudden attack of bad weather. Do a good job in compiling technical documents for winter construction. When it is determined that winter construction is needed, the chief engineer of the construction unit and various professional and technical personnel should be required to prepare technical documents in advance, formulate relevant construction organization design, construction scheme and protective measures, take all possible difficulties and problems into account, and propose corresponding solutions to nip in the bud. Arrange a special person to record the indoor and outdoor temperature of the construction site, the temperature during concrete pouring and the curing temperature of concrete. And record them for reference. Secondly, it is necessary to prepare relevant materials needed for winter construction, including engineering materials, cold-proof heating materials, various insulation materials, various insulation additives and so on. Materials can be purchased centrally to reduce costs. Materials entering the site should be managed by special personnel and stored properly to avoid waste. In addition to ensuring the quality of all kinds of materials, we must also ensure reliable sources and smooth delivery channels for emergencies.
1.2 personnel training before winter construction
Before entering the winter construction, the management personnel and professional operators on the construction site should be trained in safety production. The main contents of management training include: learning about winter construction safety specifications, learning winter construction organization design and construction technical methods compiled by the technical department, and learning daily management processes and emergency plans for winter construction. The main contents of operator training include: learning winter construction safety standards, learning winter construction safety precautions and the knowledge of winter construction operation and safety protection of this post, learning the use of various temperature measuring instruments and equipment, and learning the use of fire-fighting facilities. After the training, all trainees should be evaluated, focusing on safety standards and protective measures for winter construction. Only those who pass the exam can be employed. In addition, the project management headquarters should also equip the site construction management personnel and operators with labor protection articles such as cotton-padded clothes and gloves, arrange the life of construction personnel, pay wages on time, and solve the worries of workers. The safety officer of the construction unit should also check the electrical wiring safety of the kitchen and workers' dormitory, the heating and ventilation safety of the living quarters, and eliminate potential safety hazards.
1.3 drawing preparation and technical disclosure
When determining the winter construction project, the construction unit, design unit and technical management personnel of the construction unit should check whether the bad weather conditions during winter construction are considered in the drawing design and whether the construction technology can meet the requirements of winter construction. Such as the height-thickness ratio of the wall, whether concrete pouring can ensure the stability of the structure in cold state and other related issues. There are also problems on the drawings found by the construction unit in the preparation process, and so on. , which must be solved in the blue prints.the design. Then the construction unit carries out technical disclosure work, in order to prevent the operators of the construction team from paying attention to winter construction and not following the technological process of winter construction, but blindly constructing according to their own experience, resulting in quality accidents. The main aspects of attention are: the protection of building materials under bad weather conditions, the connection of construction procedures, the correct temperature measurement of building products, the protection and maintenance of building products, etc. Winter construction requires high requirements for raw materials. For materials entering the site, besides routine inspection, they should be rechecked before construction to avoid unqualified materials being used in the project. In the process of concrete construction in winter, some admixtures are often added, and the dosage of these admixtures will increase or decrease with the change of temperature. If it is directly used in construction without review, it is very likely that there will be major quality hazards and serious damage to the project. The technical standard of some mechanical equipment is the standard value at room temperature, which needs to be rechecked at low temperature. If it is set according to the standard value in the manual without verification, the stress bolt may be deformed due to insufficient tension at low temperature, which will make the equipment unable to work normally, affect the construction quality and even cause safety accidents.
2 winter construction subdivisional work matters needing attention
2. 1 concrete engineering
Concrete engineering is an important part of winter construction. Controlling concrete temperature in winter construction is the key to ensure the smooth construction. Firstly, the coarse and fine aggregates of concrete are heated, and the surface is covered with plastic cloth and plastic film. If there is a frozen part on the surface, measure the temperature regularly to ensure that the temperature meets the use requirements. The water temperature of mixed water can be controlled by heating the water tank, which is generally controlled at about 50℃. In order to reduce the possibility of freezing injury of concrete, the water consumption of concrete mixture ratio can be minimized, and water reducer and antifreeze can be added to ensure the normal initial setting of concrete. In order to raise the construction temperature as much as possible and shorten the initial setting time and curing time of concrete, high-grade cement and early strength cement can be selected. Concrete loses a lot of heat during transportation. In order to reduce this part of the loss, we can first ask the mixing station to increase the initial temperature of concrete, wrap a layer of insulation material outside the transport vehicle, shorten the transport time as much as possible, choose the transport route and reduce the heat loss. Before pouring concrete, the temperature should be measured on site to ensure that the mold temperature is not lower than 5℃. In the process of pouring, try to speed up the pouring and strengthen the strength of concrete. After concrete pouring is completed, straw bags, cloth bags and other materials should be used for heat preservation. Thermal insulation materials cannot be directly covered on the newly poured surface. The surface layer should be covered with 1 plastic film, and then covered with thermal insulation material. Generally speaking, the temperature is above 0℃, and 2 ~ 3 layers should be covered below 0℃ to ensure that the initial setting period of concrete is not frozen.
2.2 Earthwork
In winter, due to the cold climate and frozen soil, it is extremely difficult to dig, the loss of construction machinery is also great, and the cost of manpower and material resources is higher than usual, so it is best to grab the earthwork of new construction projects before the arrival of winter. For earthwork that must be constructed in winter, it is necessary to formulate a relatively economical and reasonable construction scheme and feasible construction technology, shorten the construction time as much as possible, and realize rapid excavation, construction and backfilling. Backfill soil should be insulated with straw mats, and attention should be paid to cleaning up the snow. When excavating earthwork near adjacent buildings, anti-freezing measures should be taken for the original building foundation, and the foundation should be dug and filled as soon as possible to avoid freezing. Attention should be paid to the removal of snow and floating ice on the roads in the construction site, and grass mats can be laid on the foundation slope to prevent slipping, so as to ensure the driving safety of construction vehicles.
3 Safety measures
Safety is the most important thing in winter construction. We should conscientiously implement the safety production norms on the construction site and strengthen the inspection and monitoring of electrical wiring equipment, construction machinery and equipment, deep foundation pit support and insulation and heating safety in daily life. Before the arrival of winter, organize professionals to conduct a comprehensive inspection of fire-fighting facilities and fire-fighting equipment used in the construction site, check the validity period of fire extinguishers, and replace unqualified ones to ensure normal use. Statistics show that 80% of most winter site fires are caused by aging wires and careless use of electricity. Therefore, the security personnel and electrical supervisor of the construction unit should conduct a comprehensive inspection of the electrical wiring of all offices, staff quarters and warehouses on site, and it is forbidden to use electric blankets and electric stoves for heating in the dormitory. For deep foundation pit support, observation points should be set up for slope support in winter to observe the situation of slope and nearby buildings, and measures should be taken in time to avoid collapse accidents. The low temperature in winter is easy to cause safety accidents. Before construction, we should organize manpower to learn the safety knowledge of winter construction, equip with safety protection articles, conduct safety training for construction personnel, and strengthen on-site safety management to ensure the safety of the project. Although winter construction does not happen frequently, if construction enterprises can arrange manpower and material resources reasonably through adequate preparation and reasonable preventive measures, the construction period will be shortened, the project quality and progress will be guaranteed, and efficient and high-quality construction projects will be made, so that construction enterprises will be more competitive in the market and realize the perfect unity of project quality and progress.
For more information about project/service/procurement bidding, and to improve the winning rate, please click on the bottom of official website Customer Service for free consultation:/#/? source=bdzd