1. For the concrete centrally maintained on the construction site, a specific maintenance plan should be put forward according to the construction object, environment, cement varieties, additives and requirements for concrete performance, and the specified maintenance system should be strictly implemented.
2. After the completion of general concrete pouring, the slurry should be covered and watered as soon as possible. For hard concrete, concrete poured in hot weather, bridge deck and other large-area exposed concrete, if possible, a shed cover can be added immediately after pouring is completed, and then covered with water for curing after slurry is collected. Covering shall not damage or pollute the concrete surface. When the concrete surface is covered with formwork, the formwork should always be moist during curing.
3. When the temperature is lower than 5℃, it shall be covered with heat preservation, and water shall not be sprayed on the concrete surface.
4. The requirement of concrete curing water is the same as that of mixing water.
5. The water curing time of concrete is usually 7d, which can be extended or shortened as appropriate according to the humidity and temperature of air, cement varieties and additives. The concrete curing time of pressure forming and vacuum water absorption construction can be shortened appropriately. When the dosage of mineral admixture is large or the temperature is low, the curing time should be determined according to the specific situation on site, and generally it should not be less than 70% of the 28-day strength.
The number of times of sprinkling water every day is to keep the concrete surface in a wet state.
When using the plastic film curing layer, all exposed surfaces should be covered tightly, and condensed water should be left in the plastic film. When spraying the chemical slurry maintenance layer, it should be proved by the test, and measures should be taken to ensure that it is not missed and there is no need to spray water for maintenance.
6. When the concrete of the structure comes into contact with flowing surface water or groundwater, waterproof measures should be taken to ensure that the concrete is not eroded by water before the strength reaches 50%, and the curing time is not less than 7d. When the environmental water is corrosive, the concrete shall be protected from water erosion within 10d and before the strength reaches 70% of the design strength. When concrete comes into contact with seriously eroded environmental water such as chlorine salt and seawater, the curing age should generally not be less than 4 weeks. In the environment with freeze-thaw cycle, it should be completed four weeks before the arrival of the ice age.
7. In order to prevent the generation of non-stressed cracks, thermal insulation measures should be taken during concrete curing to prevent the surface temperature from changing dramatically due to environmental factors (such as sun exposure and sudden drop in temperature). Especially for the maintenance of mass concrete, temperature control measures should be taken according to climatic conditions, and the surface and internal temperatures of concrete after pouring should be measured as needed to control the temperature difference within the design requirements. When the design has no requirements, the temperature difference should not exceed 25℃.
8. It is forbidden to trample before the concrete strength reaches 1.2MPa; Before the strength reaches 2.5MPa, it shall not bear the load of pedestrians, means of transport, templates, supports, scaffolding, etc.
9. When curing concrete with steam, it shall be implemented in accordance with relevant regulations.
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