How many days can the concrete be taken away from the concrete?
Plastic film maintenance refers to the plastic film Wei cover to separate the concrete and air, the water is not evaporated, cement concrete in the water to complete hydration, has reached condensation, hardening. This method can be directly covered in plastic draft on the surface of concrete, or plastic sprayed on the surface of emulsion concrete, until the emulsion of volatile, with a layer of plastic film on the surface of the concrete, in order to make the concrete component isolated from the air to the concrete moisture evaporation and no hydration complete the function. Spray plastic film maintenance is 28d concrete strength low around 8%, because the film is thin, can not be completely separated, frozen adiabatic effect, so in the summer of this method is to add sunscreen facilities (not less than 24h), or will lead to concrete cracks producing filamentous. Generally speaking, the cost of natural maintenance is low, the effect is good, but the maintenance period is long. In order to shorten the curing period, increase the turnover rate of the template and the utilization rate of the site, it is suitable for heating maintenance in general production of prefabricated components.
Cover water conservation according to the outside temperature in general should be concrete after pouring 3 material 12h with straw, Luxi, sacks, sawdust, wet soil and wet sand of the concrete cover, and regular watering to keep moist. Concrete watering maintenance date, Portland cement, ordinary cement and slag cement mixing concrete may not be less than 7 days and nights. Mixing with retarding admixture or concrete with impermeability shall not be less than 14 days and nights; when using bauxite cement, not less than 3 days and nights. The number of daily watering can keep concrete with sufficient moist condition is appropriate, when the air temperature is above 15 DEG C, in the concrete pouring after 3 days in the daytime, at least every 3 hours a night should also be watering, watering two times, after the maintenance, at least 3 times every day watering (of course, when the temperature of the drying can increase the number of water right). For the larger area (or volume) of concrete, should adopt the "water conservation" for reservoir engineering in the demolition of the internal model, concrete reaches certain strength water conservation; to the underground structure or foundation, can be renewed by brushing the surface of asphalt emulsion or soil backfill instead of water conservation.
