Temperature difference to be noticed in concrete engineering
Finished product protection
(1) When the average day and night temperature is lower than 5 ℃ or the low temperature is lower than -3 ℃, it should be treated as winter construction. When the ambient temperature is lower than 5 ℃, it is forbidden to sprinkle the concrete surface for curing. At this time, the curing liquid can be sprayed on the concrete surface, and appropriate heat preservation measures should be taken.
(2) During the curing of concrete, heat preservation measures should be taken to prevent the surface temperature of the concrete from undergoing drastic changes due to environmental factors (such as exposure, sudden temperature drop, etc.). During curing, the temperature difference between the core of the concrete and the surface, and between the surface and the environment should not exceed 20 ° C. Before the construction of mass concrete, a strict maintenance program should be formulated to control the temperature difference between the inside and outside of the concrete to meet the design requirements.
(3) After the concrete is demolded in winter and hot season, if the weather changes suddenly, appropriate thermal insulation (cold season) and thermal insulation (summer) measures should be taken to prevent the concrete from generating excessive temperature difference stress.
1. In order to prevent the large temperature difference, the steel bar should be installed as a crack prevention measure. In the area of cast-in-place slabs with large temperature and large shrinkage stress, anti-cracking structural steel bars should be arranged on both sides of the slab, the reinforcement ratio should not be less than 0.10%, and the spacing should not be greater than 200mm. The anti-cracking structure steel bar can use the original steel bar to pass through the configuration, and can also be provided with a separate steel bar and the original steel bar can be overlapped according to the requirements of the tensile steel bar or anchored in the surrounding components. At the same time, it is generally set on the surface between double columns or multiple columns.
2. Formwork engineering (1) To ensure the quality of the reinforced concrete protective layer, a formwork with permeable lining may be used when necessary. During the curing of concrete, when the temperature difference between the concrete and the environment is greater than 20 ° C, thermal insulation formwork should be used. (2) The removal period of the formwork and support (arch) frame should be determined according to the characteristics of the structure, the location of the formwork, the strength of the concrete and the temperature difference between the concrete and the environment.