1, pay attention to observe the temperature change. Concrete or mortar masonry starts from the first day when the outdoor daily average temperature is lower than +5℃ for three consecutive days or the daily minimum temperature is lower than -3℃ for three consecutive days, that is, it enters the winter construction progress. In addition to the general relevant regulations, the construction materials and techniques must also meet the specifications and requirements of winter construction.

2. Before winter comes, the personnel of the supervision project department should check the concrete production and insulation measures in winter, and check the actual temperature after lighting a fire or setting a steam boiler in the shed.

3, check the construction unit of concrete construction in winter thermal calculation results, and heating measures for water and aggregate is reasonable and feasible. The heating temperature of various materials is controlled by the temperature of the mixed mixture. When mixing concrete, the aggregate shall not contain ice, snow and frozen blocks, and the mixing time shall be extended by 50%.

4. After the winter construction concrete is approved, antifreeze and preservative are added and steam curing is used. The concrete construction mixing station adopts a fully enclosed greenhouse structure, and the steam boiler provides heat to ensure the temperature in the greenhouse and heat water, sand and stone. The concrete is transported by a concrete truck with thermal insulation sleeve.

5. Thermal test data of concrete mixture During winter construction, the temperature behind the stove and the firewall in the mixing station shed rises to 10℃, the mixing water is heated to 70℃, the temperature in the cement shed is-10℃, the sand and gravel are not heated, the discharging temperature of concrete mixture is above 15℃, and the temperature loss during waiting for discharging is not more than 2℃. The construction of pier shaft and bearing platform draws lessons from the above experience and adopts the same facilities and technology for construction.

6. Before pouring concrete, coat the pump pipe with rock wool tube and then wrap it with plastic sheets to reduce heat loss and shorten the concrete pouring time as much as possible. Construction should be arranged in the daytime when the temperature is high, and construction in rain and snow weather is not allowed.

7. The pier uses the open caisson as a fence, and a steel pipe skeleton is erected between the top of the open caisson and the formwork at the top of the pier, covered with a cotton tent, and the roof is set in a dome shape to prevent rain and snow from accumulating. There are 3-4 furnaces in the cofferdam to keep the temperature in the shed above 15℃. After the concrete pouring is completed, the pier top and ceiling will be sealed and maintained for one month. Continue to bury cooling circulating pipes in the pier to reduce the temperature, continue to mix fly ash instead of part of cement to reduce the hydration heat, reduce the temperature difference between inside and outside the concrete, and prevent temperature cracks.

8. During the curing period, assign personnel to regularly add coal to the furnace to ensure the temperature in the shed and make the concrete reach the design strength at the positive temperature. Do not sprinkle water on the concrete surface within 12h before stopping heating, and slowly cool down, with the cooling rate controlled at 3℃/h.

9, supervise and inspect the maintenance of concrete structure, using heat storage method for maintenance shall not be lower than 65438+00℃. Check the measurement of concrete temperature in the construction unit: whether the temperature measuring holes are arranged and numbered as required, and measure the temperature of concrete entering the mold as required. Whether the initial temperature of concrete curing and the temperature of concrete during heating, constant temperature and cooling meet the requirements. According to the records of curing temperature measurement, the strength growth of concrete is calculated, and the pressure test time of test blocks with the same conditions, the time of concrete formwork removal and the thermal insulation measures of concrete external surface after formwork removal are determined. The difference between the concrete surface temperature and the natural temperature during formwork removal shall not exceed 20℃.

10, the curing time in winter shall be no less than 28 days, and the time for form removal shall be appropriately extended.