1 Preparation before construction is the premise of winter construction. First of all, we should pay attention to collecting the data of winter temperature change on the construction site in advance. As the Code for Winter Construction of Building Engineering (JGJ 104-97) stipulates that winter construction will begin when the daily average outdoor temperature is stable below 5℃ for five consecutive days, it is necessary to make preparations and prevent in advance before the project is about to enter winter construction, eliminate unfavorable factors in the bud, and collect local meteorological data in advance to understand the local temperature change, duration, minimum temperature and maximum wind force. Secondly, prepare materials for winter construction.
Compiling technical documents for winter construction is the main measure for winter construction. Before the project enters the winter construction, it is necessary to prepare technical documents for winter construction in advance as technical guidance documents for winter construction, which is the main measure for winter construction. Technical documents for winter construction must include construction scheme and construction organization design or technical measures. The construction scheme and construction organization design or technical measures include the following main contents: the production task arrangement and deployment of winter construction; Construction materials approach plan; Labour force plan; Planning and deployment of heat sources and equipment; Winter construction personnel training plan; Key points of engineering quality control; Key points of safe production in winter; Construction process and schedule arrangement; Construction methods and technical measures of various subdivisional works.
3 personnel training and technical disclosure are the key to winter construction. 3. 1 Construction personnel training. Winter construction is not familiar with the rules of winter construction because it is operated at negative temperature, which is easy to cause engineering quality accidents. In order to ensure the engineering quality, personnel training must be carried out before winter construction. The training content is: (1) Learn relevant national and local winter construction codes, standards and regulations, such as the Code for Winter Construction of Building Engineering (JJ104-97). (2) Learn the basic theoretical knowledge and construction methods of winter construction. 3.2 Technical disclosure before winter construction. The purpose of technical disclosure is to prevent construction operators from violating winter construction laws, resulting in improper operation and man-made quality accidents. The key points of technical disclosure before construction are: (1) the use of raw materials; (2) heating or protection of raw materials; (3) Temperature measurement of raw materials or finished products; (4) Protection or maintenance of finished products. 3.3 to do a good job of raw materials and material mixture ratio inspection and second interview. In winter construction, all kinds of raw materials need to be rechecked to prevent unqualified materials from being used in the project. In winter concrete construction, some additives are often used. With the constant change of temperature, the dosage is different. At present, there are many fake and shoddy products. If it is directly used in the project without re-examination, it is likely to bring serious consequences to the project. In order to eliminate the factors that cause the hidden danger of engineering quality, it is necessary to re-interview the raw materials used in the project.
4. Strengthening the quality control in the construction process is an important means to do a good job in winter construction. 4. 1 Frost-resistant mortar method is mainly used in winter construction of masonry engineering. The dosage of (1) antifreeze should be implemented according to the temperature at 13 and the test mixture ratio. (2) When the outdoor temperature is lower than-10℃ and the construction needs, the raw materials shall be heated, and water shall be given priority. When the temperature calculated by thermal engineering cannot be met, the sand should be reheated, but it should be noted that the water temperature should not exceed 80℃, the sand temperature should not exceed 40℃, and the cement should not be heated, but it should be placed indoors and the temperature should not be lower than 0℃. (3) When the temperature is in the range of-10℃ ~ 20℃, the service temperature of masonry mortar is+10℃. Pay attention to the temperature loss of mixed mortar during transportation, storage and use, and it is best to use it with mixing. (4) During operation, the masonry shall be built according to the "trinity" masonry method. The mortar joint should be controlled within 10mm, and the brick masonry must be covered with thermal insulation materials after the construction is completed that day. (5) The ice, frost and snow on the brick should be removed, and generally watering is not allowed. Clinker-free cement, lime mortar or clay mortar shall not be used in winter construction masonry projects, and ice cubes shall be removed from the sand. (6) After daily masonry, the masonry surface shall be protected and covered in time, and mortar shall not be left on the masonry surface. 4.2 Control points in the process of steel bar construction (1) The most important thing in winter steel bar construction is the welding of steel bars, and the welding quality is directly related to the safety of engineering structures. There are many factors affecting the welding of steel bars in winter. Before rebar welding, trial welding must be conducted according to local construction conditions and temperature conditions. During the trial welding, the welding parameters and welding process should be adjusted according to the temperature conditions. After the welding parameters and welding process are determined, try welding. The weldments for trial welding will be sent to the laboratory for testing, and batch welding will be carried out after passing the test. (2) Quality control of covered electrode or flux. Flux or covered electrode is easy to get wet during transportation and storage in winter. Using wet flux or covered electrode will make the gas mixed in the welding pool stay in the welding meat, which will affect the quality of the welded joint. When covered electrode or flux is used, covered electrode or flux should be baked according to the requirements of the manual and dried before use. 4.3 In the process of concrete construction, the key point of quality control is to control the heating temperature of raw materials. The heating of concrete raw materials in winter construction is an important factor to ensure the early strength growth of concrete. In the process of construction, it is necessary to determine the heating temperature of raw materials, take heating measures and measure the temperature regularly to ensure that the heating temperature meets the requirements. Control the pouring temperature of concrete. In the process of construction, the pouring temperature of concrete should generally not be lower than 2℃. If the temperature is too low, it is easy to cause the fresh concrete to cool too fast, which will make the concrete drop to freezing point in a short time and affect the early strength growth of concrete. Do a good job of retaining test blocks. According to the specification, there are no less than two groups (6 blocks) of test blocks for winter construction, which are cured under the same conditions as the structure, and are used to test the strength of concrete before freezing and after 28 days of normal temperature curing. Strengthen the maintenance of finished products. The maintenance management of concrete in winter is an important measure to ensure the quality of concrete. Newly poured concrete: First, do a good job of covering and heat preservation, and check it frequently. The second is to do a good job of concrete temperature measurement, and keep abreast of the internal temperature of concrete to ensure that the initial setting period of concrete is not frozen. Key control points of steel structure engineering construction. High strength bolt connection in steel structure engineering construction. The quality of high-strength bolt connection is an important factor affecting the quality of steel structure. The torque coefficient in the product manual of high-strength bolt is the calibration value at room temperature. There are many factors that affect the torque coefficient, such as ambient temperature, final tightening time and tightening speed. , especially the environmental temperature has the greatest influence. The torque coefficient in the general product manual is the calibrated value at normal temperature, which needs to be calibrated again at negative temperature. Otherwise, it will still be controlled according to the numerical value given in the manual, which may cause the tensile stress of the bolt. Negative temperature welding in winter. There is a great difference between negative temperature welding in winter and normal temperature. When welding, welders should be trained to master the rules of negative temperature welding, and covered electrode should be baked and dried according to the instructions to ensure the welding quality and structural safety.
5. Formulate winter safety construction measures. There are many factors that cause safety accidents because of the low construction temperature in winter. Before construction, corresponding winter safety construction measures should be formulated, necessary safety protection articles should be equipped, safety education should be given to construction personnel, especially for aerial work and special types of work, and on-site construction management should be strengthened to ensure the safe construction of the project. Although winter construction doesn't happen often, if we don't prepare and prevent it in advance, it will affect the quality and progress of the project, and improper measures will bring hidden dangers to the project quality. Therefore, it is necessary to take preventive measures before the project is about to enter the winter period and control them during the construction period.
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