How much is the design strength of concrete to be qualified, and are there any relevant specificatio

The strength of each group of test blocks is guaranteed to reach 115% of the design strength level.

According to the specification "Concrete Strength Inspection and Evaluation Standard" GB T 50107-2010 test block, there may be smaller ones, such as C21For such control ability, the guarantee rate of concrete strength is very low, which cannot meet the requirements of the specification (95% or more). For example, the next test blocks are pressed out around 63.

Illustrate. Your ability to control is strong. It can be believed that the concrete strength meets the requirements.

The strength of each group of test blocks is guaranteed to reach 115% of the design strength level.

In accordance with the national standard GB 50010 2002 "Code for Design of Concrete Structures".

The concrete strength grade should be in cubes.

The standard value of compressive strength is determined.

The standard value of cubic compressive strength refers to the compressive strength of a cube specimen with a side length of 150mm made and maintained according to the standard method, and the compressive strength with a guarantee rate of 95 is measured by the standard test method at the age of 28 days, which is expressed as FCU,K.

Ordinary concrete is divided into fourteen strength grades: C15, C20, C25, C30, C35, C40, C45, C50, C55, C60, C65, C70, C75 and C80. Concrete strength grade is an important basis for concrete structure design, construction quality control and engineering acceptance.

Different construction projects and construction parts need to use concrete of different strength grades, and generally have a certain range of options.

Precautions for concrete foundation construction are as follows:

1) The foundation groove (pit) should be inspected, the local weak soil layer should be dug out, and the ash or gravel layer backfill should be tamped to the substrate level. And clean the foundation groove (pit).

2) If the foundation soil quality is good and there is no groundwater, the first stage of the foundation groove (pit) can be poured with the original groove (pit), but the size should be guaranteed to be correct and the mortar will not be lost. The upper step should be poured with formwork and supported by the formwork.

It should be firm, the cracks and holes should be plugged tightly, and the wooden mold should be watered and moistened.

3) The pouring height of the foundation concrete is less than 2m, and the concrete can be directly unloaded into the foundation groove (pit), and the concrete can be filled with corners; When the pouring height is more than 2m, the ash should be lowered through the funnel, string drum or chute.

The above content refers to Encyclopedia - Design Code for Concrete Structures.

If your project is not very large, and the number of concrete test blocks is not large, a simple judgment method (according to non-mathematical statistics) is, first of all, the strength of each group of test blocks is guaranteed to reach 115% of the design strength level.

The standard according to is: "Concrete Strength Inspection and Evaluation Standard" GB T 50107-2010

Answer: The design strength of concrete should reach: not less than the design strength and less than the standard strength of the compressive strength of the concrete cube, and the strength value of the previous grade is qualified; The relevant specifications include the "Standard for Test Methods for Mechanical Properties of Ordinary Concrete".

The requirement for the test block is to meet the design strength, and it is not mentioned how much it cannot be exceeded, but if the strength exceeds 150% of the design value, it means that it is very likely that there is a problem in a certain linkRaw materials, production process, test block production and maintenance, to find reasons in these aspects. If the strength of the test block is too high, the management level is unqualified, then there is a potential quality risk, and all the strength should not be paid the same attention.

According to the standard compressive strength, the strength grades of concrete are divided into 19 grades: C10, C15, C20, C25, C30, C35, C40, C45, C50, C55, C60, C65, C70, C75, C80, C85, C90, C95, and C100.

The tensile strength of concrete is only 1 10 1 20 of its compressive strength. Improving the ratio of tensile and compressive strength of concrete is an important aspect of concrete modification.

Classification by apparent density.

According to the apparent density, concrete can be divided into: heavy concrete, ordinary concrete, and light concrete. The difference between these three types of concrete is the difference in aggregate.

Heavy concrete is made with an apparent density greater than 2500kg m and is made with a particularly dense and particularly heavy aggregate. Such as barite concrete, steel chip concrete, etc., they have the properties of opaque X-rays and rays.

Ordinary concrete is the concrete we commonly use in construction, with an apparent density of 1950 2500kg m, and the aggregate is sand and stone.

Lightweight concrete is concrete with an apparent density of less than 1950kg m. It can be divided into three categories:

1. Light aggregate concrete, its apparent density is 800 1950kg m, light aggregate includes pumice, volcanic slag, ceramite, expanded perlite, expanded slag, slag, etc.

2. The apparent density of hollow concrete (foam concrete, aerated concrete) is 300 1000kg m. Foam concrete is made from cement slurry or cement mortar with stable foam. Aerated concrete is made of cement, water and gassing agents.

3. Macroporous concrete (ordinary macroporous concrete, light aggregate macroporous concrete), there is no fine aggregate in its composition. The apparent density range of ordinary macroporous concrete is 1500 1900kg m, and it is prepared with crushed stone, soft stone and heavy slag as aggregates. The apparent density of light aggregate macroporous concrete is 500 1500kg m, which is prepared with ceramsite, pumice, broken bricks, slag, etc. as aggregates.

If it is not a very large project, when the number of concrete test blocks is not large, a simple judgment method (according to non-mathematical statistics) is, first of all, the strength of each group of test blocks is guaranteed to reach 115% of the design strength grade.

The standard according to is: "Concrete Strength Inspection and Evaluation Standard" GB T 50107-2010

It should be the difference between any two of the three numbers divided by the average of the three numbers, if it is greater than 15%, it is considered that the concrete engineering represented by this test block is unqualified. It's not that the higher the strength, the better.

It's too much super strong, and it should be considered unqualified.

But it's easy to solve, please design a modification to say that you can use such high-strength concrete.

So much ultra-high, how can it be unqualified?

It is not economical or cost-effective;

Maybe not credible, the quality supervision committee doubts the authenticity of the witness sampling or test results, if you are on-site coring, the strength can indeed meet this standard, then it should be evaluated!

This is related to the specific policies of each quality supervision station, such as our here, the district generally cannot exceed 150%, but the city can not exceed 200%, it is best to consult your current boss or local counterparts! If it exceeds the proportion they stipulate and becomes the object of suspicion, it may be physically cored!

The intensity can reach about 50% of the design value in 3 days, 70-80% in 7 days, and 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.

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

Conservation purposes. After the concrete is poured, if the climate is hot and the air is dry, if the maintenance is not carried out in time, the water in the concrete will evaporate too quickly, forming a dehydration phenomenon, which will make the cement particles that have formed a gel body can not be fully hydrated, and the pin cavity rubber can not be converted into stable crystals, and lack sufficient cohesion, so that it will fall off in flakes or powders on the surface of the concrete. In addition, when the concrete does not have sufficient strength, the premature evaporation of water will also produce large shrinkage deformation and dry shrinkage cracks.

The above content reference: Encyclopedia - concrete curing.

What is the design strength of concrete for general house construction?

Pro, the design strength of concrete for general house construction is C20

The strength grade of concrete refers to the compressive strength of the concrete. The strength grade of concrete should be divided by the standard value of the compressive strength of the concrete cube. The symbol c is used with the standard value of the compressive strength of the cube (in n mm 2; or MPA meter).

According to GB50010-2010 "Code for Design of Concrete Structures", ordinary concrete is divided into 14 grades, namely: C15, C20, C25, C30, C35, C40, C45, C50, C55, C60, C65, C70, C75, C80. For example, concrete with a strength class of C30 is 30 MPasfcuk < 35 MPa

Concrete, for short"(tong)": refers to the general term of engineering composite materials that cement aggregates into a whole by cementitious materials. The word concrete usually refers to the use of cement as cementitious material, sand and stone as aggregates

Cement concrete, also known as ordinary concrete, is widely used in civil engineering engineering when it is mixed with water (which can contain admixtures and admixtures) in a certain proportion and is mixed to obtain cement concrete.

Have a great day! Praise thank you

The standard deviation of the design strength of concrete is the ratio of concrete to the butt.

There are detailed regulations in the design specifications:

Concrete strength standards.

The difference should be calculated and determined according to the statistical data of the same type of concrete, and should meet the following requirements:

1.When calculating, the number of strength specimen groups should not be less than 25 groups;

2.When the concrete strength grade.

C20 and C25 grades, when the calculated value of the standard deviation of the strength is not less, the standard deviation used to calculate the strength of the preparation should not be less than; When the strength grade of concrete is equal to or greater than C30 grade, and the calculated value of the standard deviation of the strength is less than that, the standard deviation used to calculate the strength of the preparation should not be less than.

3.When there is no statistical data to calculate the standard deviation of concrete strength, its value should be taken according to the current national standard "Code for Construction and Acceptance of Concrete Structure Engineering" (GB50204). In GB50204, it is specified that the standard deviation of concrete with a parallel punch less than C25 is taken, between C25 and C30, and for concrete greater than C35, it is taken.

The standard deviation of concrete strength should be calculated and determined according to the statistical data of the same kind of concrete before returning to the cherry tree, and when there is no statistical data, it can be selected according to the provisions of the national standard GB50204

Concrete strength grade: Ridge hunger below C20

C20-C35 is higher than C35

Railway concrete works can be pressed:

Strong regret grade: less than C20

c20-c40

Higher than C40 component factory:

Mixing plant :

The concrete strength should reach between 70% and 90% of the design strength.

The effect of humidity on the strength of concrete is achieved by affecting the hydration and hardening of cement. When the temperature is suitable and the humidity is high, the strength develops quickly, and on the contrary, it is not conducive to the growth of concrete strength.

The cube or cylindrical specimen is used, and a cushion strip is added between the upper and lower supporting surfaces of the specimen and the press pressing plate, so that the corresponding strip loading is formed up and down the specimen to cause the splitting failure of the specimen along the center of the cube or the diameter section of the cylinder, and the axial tensile strength of the concrete can be obtained by converting the force value at the time of splitting.

If the laboratory sampling procedures and post-maintenance are strictly followed, theoretically the design strength can reach about 70 in 7 days and more than 90 in 28 days. But this is only theoretical, if you are a large volume of concrete, or other special requirements, or the curing sampling is not up to standard, don't worry!