3 days, 7 days, 28 days standard strength of concrete?

The strength of concrete is determined according to the temperature, curing conditions, and time, and there is no standard strength concept of 3 days, 7 days, and 28 days. There is only a standard value for concrete, such as C25. There are also differences in whether the concrete is self-mixed or ready-mixed pumping on site, the initial setting time, and the slump.

all affect the strength of concrete. The standard curing is 28 days for strength assessment, and the same condition curing is in Celsius.

600 degrees days to carry out strength evaluation, impermeable concrete.

It takes 60 days. When the concept is clear, the problem is clear.

The standard strength of concrete refers to the strength of 28 days under standard curing conditions. In real life, often due to actual needs, 7 days of concrete standard curing test blocks are added for testing to estimate the strength of 28 days for reference. Generally speaking, the strength should reach more than 80% of the design strength in 7 days.

It is understood that there is no such thing as a 3-day intensity. In addition to meeting the design strength, that is, 100%, the 28-day strength should also meet the standards for the evaluation of concrete strength.

Generally speaking, as long as the concrete test block is made and cured according to the specification, the strength can basically reach about 50% of the design value in 3 days, 70-80% in 7 days, and about 100% in 28 days, or even higher.

The 28-day strength of concrete is implemented immediately according to the evaluation standard, GB T50107-2010 new standard.

Assessed and non-assessed. 3D is generally more than 30%, 7D60 is above, most of them are above 70, 28D If the strength of the monoblock reaches more than 115%, then all are qualified, if not enough, you can refer to the standard to participate in the assessment.

As long as the concrete test block is made and cured according to the specification, the strength can basically reach about 50% of the design value in 3 days, 70-80% in 7 days, and about 100% in 28 days, or even higher.

Artificially create 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 curing time depends on the cement type, such as ordinary Portland cement concrete, not less than 7 days and nights. The latter is suitable for high-rise structures and large-area concrete structures that are not easy to be cured by sprinkling, and the perchloroethylene resin plastic solution is sprayed on the concrete surface with a spray gun.

After the solution volatilizes, a thin film is formed on the surface of the concrete, which isolates the concrete from the air, prevents the evaporation of water in the concrete, ensures the normal hydration of the cement, and the film can age and fall off by itself after the curing is completed.

Hello, I have seen your question and am preparing the answer, please wait a moment Hello, under normal curing, the strength of concrete can reach 40% 50% of the design value in 3 days, 70%-80% in 7 days, 80% 90% in 14 days, about 100% in 28 days, or even higher. 3 days, 7 days, and 14 days are the reference intensity and cannot be used as the final evaluation basis, and 28 days are the standard intensity and cannot be used as the final evaluation basis.

As long as the concrete test block is made and cured according to the specification, the strength of the concrete can basically reach about 50% of the design value in 3 days, 58% in 7 days, 79% in 14 days, and about 100% in 28 days, or even higher.

Concrete can reach strength after 28 days, during which one is the solidification phase and the other is the growth phase. The setting time is within 8 hours after pouring, and the strength growth period does not reach the expected strength until 28 days after pouring, and will slowly grow over the next 6 months.

Instructions for concrete curing times

1. The standard curing period of concrete specimens is 28 days, and its compressive strength is tested.

2. After the concrete is poured, it should be covered and moisturized within 12 hours. For the concrete mixed with silicate cement, silica cement and slag cement, the curing time should not be less than 7 days; For concrete mixed with coagulant admixtures or impermeability requirements, the curing time should be more than 14 days.

3. After the construction of the overall surface layer project is completed, the maintenance time should be more than 7 days. After the compressive strength reaches 5MPa, it can be walked on concrete.

The strength of concrete can basically reach about 50% of the design value in 3 days, 70-80% in 7 days, and about 100% in 28 days, or even higher.

Concrete has the characteristics of abundant raw materials and simple production process, so that the amount of concrete is getting larger and larger, and concrete has the characteristics of high compressive strength, good durability and wide range of strength grades.

These characteristics make it widely used, not only in various civil engineering projects, but also in shipbuilding, machinery industry, marine development, geothermal engineering, etc., concrete is also an important material.

Precautions for beating concrete:

1. When putting concrete into the mold, do not inject a large amount of concrete into the impact formwork or steel frame. If the height of the concrete pouring is more than 2m, the tandem pipe and slide pipe should be used for cutting, and the drop height between the discharge nozzle and the pouring layer should be kept within it.

2. If you plan to pour concrete twice, the interval should usually not exceed 1 hour and 30 minutes, and the vibrator must be continuously stirred at the handover position.

3. In the process of pouring concrete, when the concrete surface floats, there are no bubbles and will not sink, the vibrating rod should always be used to vibrate. When using a vibrator, it is necessary to carry out continuous movements in a determined order, and the position of each movement should not exceed 40 cm to avoid leakage or excessive vibration.

4. After a rough estimate of the remaining amount of concrete and the remaining amount of concrete, the required quantity should be discussed with the construction manager of the batching plant and a reasonable schedule should be formulated.

Hello, I'm glad to answer your questions, please wait a minute, oh kiss and ask a question, my cement pavement has been poured for 5 days, and there are a few days to pass the heavy-duty car, because in the curing process of cement, in the time intensity curve, 3 days, 7 days, 28 days, these three time periods are obviously representative. Within 3 days, the strength of cement is growing rapidly. Generally, it can reach more than 75% of the maximum strength, and can be used basically.

Within 3 to 7 days, the strength growth of cement slows down, and generally reaches more than 95% of the maximum strength, which can be used completely. After 7 days, the cement strength increases more slowly, and by 28 days, the cement strength reaches its maximum. 14 days is a median value, and it will not increase after 28 days.

Therefore, the national standard regards these few days as several basic time points to measure the strength of cement.

Question: Can I pass for 10 days?

Depending on the level of your pouring, if you maintain it properly, it will take seven days to pass the small car, and at least 14 days to pass the large car, generally about 28 days.

Hope it can help you kiss it.

Question: PC425 cement, thickness 20 cm, is there an 8 mm steel bar in the middle?

Yes, please wait a minute.

Purely in terms of pressure, there should be no problem, but it is difficult to guarantee that it will not crack, and it will take at least 12 days to kiss.

There is a battlefield to ask questions, and I am afraid of being crushed by a cart.

At least 12 days to pass the heavy vehicle.

Question: Is the temperature 10 not guaranteed now?

Kiss! Hello, happy to answer your <>

The strength of pro-concrete for 3 days, 7 days, 14 days and 28 days is as follows: the strength of concrete can reach 50% in 3 days, 70-80% in 7 days, about 100% in 28 days, or even higher in 14 days. The strength of concrete reaches 70 80% in 14 days, 45 55% in 7 days, and 100% in 28 days.

The quality of concrete is closely related to the type, amount and method of admixture. The strength of concrete can only ensure normal development under the condition that temperature and humidity are suitable, and it should be maintained in accordance with the provisions of the construction code. In summer, it is necessary to prevent exposure to the sun, and make full use of the time when the temperature is high and low in the morning and evening to pour concrete; Minimize transportation and pouring time, prevent exposure to the sun, and increase the slump of the mixture when it comes out of the tank

Intermittent watering should not be done during curing, because the temperature of the concrete surface rises when it is dry and cools when it is watered, and this alternating effect of cold and heat will reduce the strength and crack resistance of the concrete. I hope mine can help you! Do you have any other questions?