How many days to maintain a 3 meter deep concrete foundation in winter

The number of days of curing should vary according to the local temperature.

Appendix D of the Code for Acceptance of Construction Quality of Commercial Concrete Structure Engineering stipulates that the strength inspection of curing specimens under the same conditions for structural entity inspection stipulates: "The equivalent curing age of natural curing specimens under the same conditions and the corresponding representative value of specimen strength should be determined according to the local temperature and curing conditions according to the following provisions:

1.The equivalent maintenance period can be taken according to the daily average temperature when the cumulative amount reaches 600 ·d, and the age period of 0 and below is not included. The equivalent curing period should not be less than 14 days, and should not be greater than 60 days;

2.The strength representative value of the curing specimen under the same conditions should be determined according to the strength test results according to the provisions of the current national standard "Commercial Concrete Strength Inspection and Evaluation Standard" GBJ107, and then multiplied by the conversion factor; The conversion factor should be taken as, and it can also be adjusted appropriately according to the local test statistics. ”

Generally, within 12 hours after the completion of pouring, the commercial concrete should be moisturized and cured and covered, curing time: the use of Portland cement, ordinary Portland cement or slag Portland cement mixed commercial concrete, shall not be less than 7 days, mixed with retarding admixtures or impermeability requirements of commercial concrete shall not be less than 14 days, watering times should be able to keep the commercial concrete in a wet state, maintenance water should be the same as mixing water, if you want to soak all the water on it, soak it, Note: Do not water if the average temperature of the day is below 5 degrees Celsius.

Cover the cured commercial concrete with plastic sheeting, and the entire exposed surface should be tightly covered, and condensation should be kept in the plastic sheeting.

The standard curing time for concrete is 28 days; The humidity is not lower than 95%.

The curing of concrete includes natural curing and steam curing. During the curing of concrete, the humidity and temperature control of concrete should be strengthened, the exposure time of surface concrete should be minimized, and the exposed surface of concrete should be closely covered in time (tarpaulin, plastic sheet, etc.) should be used to prevent surface moisture evaporation. Before the initial setting of the concrete of the protective layer of the exposed surface, the covering should be rolled up, and the surface should be rubbed with a trowel at least twice to make it smooth and covered again, and it should be noted that the covering should not directly touch the concrete surface until the concrete is finally set.

The steam curing of concrete can be divided into four stages: static stop, heating, constant temperature and cooling, and the steam curing of concrete should meet the following requirements:

1) During the static stop period, the ambient temperature should be kept not lower than 5, and the temperature can only rise after the pouring is finished for 4 6h and the concrete is finally set.

2) The heating rate should not be greater than 10 h.

3) During the constant temperature period, the internal temperature of the concrete should not exceed 60, and the maximum should not exceed 65, and the constant temperature curing time should be determined by the test according to the requirements of the demoulding strength of the component, the concrete mix ratio and the environmental conditions.

4) The cooling rate should not be greater than 10 h.

It really depends on what kind of foundation concrete you have, the foundation concrete of the bridge category generally has a strength requirement, which can not be specified in the maintenance time, for example, the concrete test block is retained in summer, and the superstructure construction is carried out in accordance with the general strength requirements, the test block can be sampled in 7 days, and the strength requirements are higher, such as pier stud concrete construction, which requires the construction of the pile foundation concrete test block after 28 days of strength test.

Highway engineering general foundation concrete summer maintenance 5 to 7 days is enough, if it is the need to backfill earthwork backfill materials or pipeline foundation concrete summer construction should be OK. Winter is not easy to say, you need to see your winter maintenance measures and the ambient temperature, the temperature is less than 5-10 degrees, basically have to take more than 10 days to dismantle the mold for construction.

How do you maintain concrete after it has been poured? I'm sure more than half of them don't get it right.

The concrete should be covered and cured within 12 hours after pouring, and the dry hard concrete should be cured immediately after pouring, and the average temperature of the day is lower than 5 degrees, and no watering shall be allowed.

The curing time of concrete shall not be less than 7 days, and shall not be less than 14 days when pozzolana cement, fly ash cement, mixed with retarding admixtures or concrete with impermeability requirements.

After curing for 2 to 3 days, you can remove the mold for backfilling, and the curing effect can also be achieved after backfilling.

Silicate, ordinary Portland cement concrete curing is not less than 7 days.

Large-volume concrete, other cement concrete curing is not less than 14 days.

Not less than 7 days in winter.

No less than 14 days of maintenance in summer.

1. Ordinary concrete curing.

1 Maintenance method: moisturizing maintenance and natural maintenance. Moisturizing and curing are commonly used by sprinkling, covering, spraying and other methods;

2. The concrete should be cured before its final setting, usually within 8 to 12 hours after the concrete is poured;

3. The curing time of concrete mixed with silicate, ordinary silicate and slag cement shall not be less than 7 days; The curing time of concrete mixed with volcanic ash and fly ash cement shall not be less than 14 days; Mixed with retarding admixtures, impermeable concrete, not less than 14 days.

4 During non-winter construction, concrete curing is mainly moisturizing.

Second, waterproof concrete curing.

Curing should be carried out immediately after final setting, and the curing time should not be less than 14 days.

3. Large-volume concrete curing of foundations.

1. Maintenance method: moisturizing method and heat preservation method;

2 Cover and water within 12 hours after concrete pouring. The curing time of concrete made of ordinary Portland cement is not less than 14 days; The curing time of concrete mixed with slag cement and pozzolane cement is not less than 21 days.

Fourth, post-pouring with concrete curing.

Wet cover for at least 14 days.

Ask me.

Generally, within 12 hours after the concrete is poured, the concrete is covered and moisturized and cured; The time of watering and curing is determined according to the cement variety used in the concrete. Portland cement, ordinary Portland cement or slag Portland cement mixed concrete shall not be less than 7d; The concrete mixed with retarding admixtures or impermeability requirements shall not be less than 14d.

During the curing of the concrete formwork, measures such as mold wrapping, watering, and spraying should be taken for moisturizing and moist maintenance to ensure that the joints of the formwork do not lose water and dry. In order to ensure the smooth removal of the formwork, the formwork can be slightly loosened after the concrete is poured for 24 48h, and continue to water and curing until the mold is removed, and then continue to moisturize to the specified age.

After the concrete removes the surface covering or dismantling the mold, the concrete should be moist cured by measures such as water storage, watering or covering and sprinkling, and when the concrete surface is in a wet state, the exposed surface concrete can be quickly covered or wrapped with materials such as linen cloth and straw curtain, and then covered with moisturizing materials such as linen cloth and straw curtain with plastic cloth or canvas. During the cladding, the cladding should be intact, overlapping with each other completely, and the inner surface should have condensation droplets. Conditional lots should be extended as much as possible for the coating and moisturizing curing time of concrete.

The curing time of concrete is 7 days. The dismantling time of the lower support frame of the beam must be 28 days after the regulations.

The time of concrete concrete foundation beam backfill is mainly related to the curing intensity of the beam, and the supervision unit can be backfilled with other units through acceptance.

The foundation beam is simply a beam on the soil layer of the foundation. The foundation beam is generally used for frame structure, frame shear wall structure, the frame column falls on the foundation beam or the intersection of the foundation beam, and its main role is to serve as the foundation of the superstructure and transfer the upper load to the foundation. The foundation beam refers to the beam with the top of the cushion as the bottom formwork.

28 days. In order to explore how strong the freshly poured concrete can be before it freezes in order to basically avoid frost damage, a large number of experiments have been done in various countries. China's current regulations stipulate that this critical intensity value is 40% of the normal maintenance intensity for 28 days, and is not less than 5 megapascals.

This is the basis for the winter construction of concrete.

1. When the minimum temperature is not lower than -15 °C, and the surface coefficient (ratio of surface area and volume) of the structure is not greater than 5 for surface or underground projects, the heat storage method should be used;

2. If the surface coefficient of the structure is above 5, it is required to obtain early strength, and the power conditions are better, the electric heating method can be used;

3. When the surface coefficient of the structure is large, such as columns, beams, plates, etc., and there is sufficient steam to be used, the steam method can be used.

The effect is all for heat preservation The specific method is selected according to the temperature and cost.

Minimum duration of curing of different concrete:

After the concrete is poured, the reason why it can gradually solidify and harden is mainly because of the result of cement hydration, and hydration requires appropriate temperature and humidity conditions, so in order to ensure that the concrete has suitable hardening conditions and its strength continues to grow, the concrete must be cured.

After the initial setting, cover and cure, and start watering (12 hours) after the final setting. Ensure the wetness of the concrete. The curing time is related to the component project, cement varieties and whether there is any additives, and the commonly used five kinds of cement should be no less than 7 days under normal temperature conditions; Items mixed with admixtures or with impermeability and antifreeze requirements should be no less than 14 days.

Concrete curing is artificially created by certain humidity and temperature conditions, so that the newly poured concrete can be normal or accelerate its hardening and strength growth. The fact that concrete can gradually harden and increase in strength is the result of cement hydration, which requires certain temperature and humidity conditions. If the surrounding environment does not exist for such conditions, the concrete needs to be cured manually.

The date of concrete watering and curing shall not be less than 7 days and nights for Portland cement, ordinary cement and slag cement mixed concrete.

Let's take a look at it for yourself.

First of all, the concept of natural curing of concrete refers to the maintenance measures taken on concrete under natural temperature conditions (higher than +5 °C), such as covering, watering and wetting, windblocking, and heat preservation.

Natural curing can be divided into two types: mulching, watering, curing, and plastic film curing.

1) Mulching watering and curing is based on the outside temperature, generally should be used within 3-12 hours after the concrete is poured with appropriate materials such as straw curtains, reed mats, sacks, sawdust, wet soil and wet sand to cover the concrete, and often watered to keep it moist. The date of concrete watering and curing shall not be less than 7 days and nights for Portland cement, ordinary cement and slag cement mixed concrete. Concrete mixed with retarding admixtures or impermeability requirements shall not be less than 14 days and nights; When using bauxite cement, it should not be less than 3 days and nights.

The number of watering per day has been able to keep the concrete has enough moist state as appropriate, when the temperature is above 15 °C, in the 3 days and nights after the concrete is poured, at least once every 3 hours during the day, and should be watered twice at night, in the future maintenance, at least about 3 times a day (of course, when the temperature is dry, you can increase the number of watering appropriately).

For larger areas (or volumes) of concrete, "water storage and curing" should be used, and for water storage tank projects, the inner mold can be dismantled, and the concrete can be watered and cured after reaching a certain strength; For underground structures or foundations, asphalt emulsion can be applied to the surface or backfilled with soil instead of sprinkling for curing.

2) Plastic film curing refers to the separation of concrete from air with plastic film covering, the moisture is not evaporated, and the cement has reached coagulation and hardening by the water in the concrete to complete the hydration effect. This method can directly cover the plastic draft on the surface of the concrete, or spray the plastic emulsion on the surface of the concrete component, and wait until the emulsion volatilizes, and combine it into a layer of plastic film on the surface of the concrete, so that the concrete component is isolated from the air, so that the water in the concrete will no longer evaporate and complete the hydration effect. The disadvantage of spraying plastic film curing is that the strength of 28D concrete is about 8% lower, and because the film is thin, it can not completely achieve the effect of thermal insulation and frost isolation, so in summer, this method should be added with sunscreen facilities (not less than 24h), otherwise it will lead to filamentous cracks in concrete.

In general, the natural maintenance cost is low, the effect is good, but the maintenance period is long, in order to shorten the maintenance period, improve the turnover rate of the template and the utilization rate of the site, it is suitable for heating and curing when the prefabricated components are generally produced.

How does concrete condense and how many days does it take to reach its strength? Today is a long time to see.

Not less than seven days in summer and no more than four days in winter.