Winter is the most difficult season for concrete construction. If the temperature is too low, not only will the construction speed be slowed down, but the normal hydration of the concrete will also be affected, which will slow down the strength growth of the components, which directly threatens the project quality and construction progress. How to overcome this unfavorable factor has become a major challenge facing engineering construction at present.
Due to the tight construction schedule and heavy tasks, winter is about to enter. In response to the local climate characteristics, in order to ensure the quality and progress of the project, some units ordered multiple Nobis concrete curing steam generators to abandon the traditional water-sprinkling coating curing method and adopt the steam curing method to achieve automated control of concrete steam curing.
The reason is simple. Although the traditional method is effective, relying solely on the heat storage of the concrete hydration reaction after coating cannot ensure temperature balance and stability. The strength of the concrete increases slowly and the quality of the project is prone to problems. However, it is worthwhile to use the circulation of steam to maintain the balance and stability of temperature and humidity, and to use its uniform maintenance characteristics to achieve effective control of maintenance quality.
Steam health technology
Scope of application: When the outdoor temperature is higher than 5℃, but due to the long period of the natural curing method of sprinkling water, in order to improve the utilization rate of turnover materials such as molds and bases and improve production efficiency, the steam curing method should be used to eliminate the influence of various adverse environmental factors .
Layout of steam pipes: Concrete construction is carried out in autumn. The concrete itself loses moisture quickly, especially during the day. It is advisable to pour and cover in sections; lay out steam pipes that have been processed in advance before covering, and then lay them at one end of the steam curing shed after they are fully covered. Turn on the steam for health care.
【Pre-cultivation stage】
Under normal circumstances, the pre-curing period of concrete steam curing is 2 hours, which is the time interval from the completion of concrete pouring to the start of steam. In autumn, because the concrete itself loses water quickly, 1 hour after the pre-curing period begins, a steam generator is used to send steam to the steam-curing shed three times, each time for 10 minutes.
【Constant temperature stage】
The constant temperature period is the main period for the strength growth of concrete. Normally, the main technical parameters of the constant temperature period are: constant temperature (60℃~65℃) and constant temperature time of more than 36 hours.
【Cooling stage】During the cooling period, due to the rapid vaporization of the water inside the concrete, as well as the shrinkage of component volume and the generation of tensile stress, if the cooling speed is too fast, the strength of the concrete will be reduced, and even quality accidents will occur; at the same time, during this stage, if Excessive water loss will affect later hydration and later strength growth. Therefore, during the cooling period, the cooling rate must be controlled to ≤3°C/h, and the shed can not be lifted until the temperature difference between the inside and outside of the shed is ≤5°C. The formwork can only be removed 6 hours after the shed is lifted.
After the components are opened and the formwork is removed, the components still need to be sprayed with water for maintenance. The maintenance time is ≥3 days and ≥4 times a day. Prefabricated construction in winter cannot be careless. After the concrete is poured, a more important maintenance process must be carried out to control the temperature and humidity of the external environment of the box girder to avoid hidden quality hazards caused by too low temperatures.
The first 3 days after the completion of concrete pouring are the critical time for improving the strength of the components. Traditional curing methods generally take 7 days to reach the tensile strength requirements. Now the steam curing method is used for curing. The strength increases faster than ordinary curing and the growth is stable. It ensures that the concrete reaches the formwork removal strength as early as possible, shortens and saves the construction cycle time, guarantees the construction period, and allows The construction of the Jiasa River Bridge is accelerating again.
Post time: Nov-09-2023
