Can anyone tell me the evaluation standard for the 28 day strength of concrete specimens, and how to

Calculate the average intensity of the survey area = the sum of the intensities of each survey area and the number of survey areas.

Calculate the standard deviation = the square of all numbers minus the square of the mean multiplied by the number of numbers, divide the result by the number of numbers minus one, and then open the root number of the obtained values, and the number obtained is the standard deviation of this set of numbers.

When inspected by batch, the presumptive value of concrete strength = standard deviation of the average strength of the survey area.

With a spring-driven weight, through the impact rod (force transmission rod), the concrete surface is struck, and the distance of the hammer is measured back, and the rebound value (the ratio of the distance to the initial length of the spring) is used as an index related to strength, and it is a method to infer the strength of the concrete pants.

Since the measurement is carried out on the surface of concrete, it should belong to the surface hardness method of limb purification, which is a detection method established based on the correlation between the hardness and strength of the concrete surface.

According to the Chinese national standard "Standard for Test Methods for Mechanical Properties of Ordinary Concrete" (GB T 50081-2002), the strength grade of concrete is determined based on the 28-day compressive strength. Generally, 28-day compressive strength is a common indicator to evaluate the strength of concrete.

According to the standard, the strength grade of concrete is expressed as Cxx, where XX represents the standard value of 28-day compressive strength in MPa.

If the 28-day compressive strength of a given concrete standard specimen is 24MPa, then the strength grade should be C20. In the Chinese concrete standard, C20 indicates that the standard 28-day compressive strength of concrete is 20MPa to 24MPa.

It should be noted that the specific determination of the strength grade also involves other factors, such as the design draft, engineering use, etc. In actual rot applications, in addition to the 28-day compressive strength, other concrete performance indicators, such as flexural strength, early strength, etc., need to be considered to determine the most suitable concrete strength grade for specific engineering needs. Therefore, in specific projects, Jianhexiang needs to consider multiple factors to determine the most suitable concrete strength grade.

Hello, dear, the method of judging the strength of concrete specimens is: 1For concrete with the same mix ratio that does not bend more than 100 cubic meters, sampling shall not be less than once; 2.

When the concrete of the same mix ratio is less than 100 trays mixed in each working shift, sampling shall not be less than once; 3.When a continuous pouring is poured more than 1000 cubic cars; per 200 cubic meters; Sampling once; For each floor, the concrete of the same mix ratio shall be sampled not less than once; 4.At least one set of standard curing test blocks should be retained for each sampling, and the number of indwelling groups for curing test blocks under the same conditions should be determined according to actual needs.

Hello, the method of judging the strength of concrete specimens generally adopts the compressive strength test, and there are usually three methods: (1) compressive breaking posture failure test: the compressive load is applied to the concrete specimen in the vertical direction, and the parameters such as the time, load and stress area of the specimen are recorded to calculate the compressive strength of the concrete.

2) Compressive and tensile test: the compressive load is applied to the concrete specimen in the vertical direction, and the tensile load is applied in the horizontal direction at the same time, and the deformation of the test specimen is recorded when the test piece is not the same load, so as to calculate its compressive strength. (3) Compression and slip test:

On the basis of the compressive and tensile test, a slip load is applied in the horizontal direction to calculate the slip strength of the concrete.

Medium strength mpa of compressive rock of concrete specimen = rough mountain failure load of specimen (n) bearing area of specimen (mm2).

Calculations should be accurate to: )

When the strength grade of coagulated soil is C60, the strength values measured by non-standard specimens should be multiplied by the size conversion factor.

Take "concrete cube specimen specifications 150*150*150mm and 100*100*100mm" as an example:

Its value is: for 200mm 200mm 200mm specimen;

For 100mm 100mm 100mm specimens.

When the concrete strength grade is C60, it is advisable to use the standard specimen 150mm 150mm 150mm specimen. The conversion factor of 150mm 150mm 150mm specimen is.

For example, the compressive strength of the three test blocks of 100*100*100mm with a failure load of 335kn, 352kn and 318kn is equal to = (335000 + 352000 + 318000) 3 (100 * 100) = because 100 * 100 * 100 is a non-standard test piece so its compressive strength = coefficient ) The failure load of the three test blocks is 424kn, 401kn and 396kn is equal to = (424000+). 401000+396000) 3 (150*150), because 150*150*150 is the standard specimen, so its compressive strength = coefficient) =.