How to assess whether the strength of the concrete test block is qualified?

Assess the strength of concrete.

The size conversion coefficient of the size and strength of the concrete specimen used should be taken as follows: the scale molding method, the scale curing premise and the strength test method should meet the requirements of the relevant national specifications. That is, a cube with a side length of , made according to the scale method.

Specimens at a temperature of relative humidity.

Under the premise of a scale of more than 0$1 in the environment or water 2 curing to %34 years of age, the compressive degree of the concrete cube measured by the scale test method.

The newly promulgated and implemented "Code for Acceptance of Construction Quality of Concrete Structure Engineering" requires that the concrete strength and reinforcement protective layer of the structural entity should be dealt with during the acceptance of the sub-division project.

The two important indexes of thickness are re-inspected, and the use of the same premise curing specimen to determine the strength of concrete is an important means and content of structural physical maintenance. At the same time, there are clear provisions in the evaluation of concrete strength, the division of acceptance batches and the treatment of evaluation differences.

Concrete strength overhaul evaluation scale", concrete strength should be overhauled and assessed in batches according to the acceptance batch. The concrete of an acceptance batch shall be composed of concrete with the same strength grade, the same age, and the same production process premise and mix ratio. The information is referred to Xinhuanet.

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Qualified standards for the compressive strength of cement concrete.

When there are 10 groups of specimens, they should be evaluated by mathematical statistics according to the following conditions

rn - k1sn≥

rmin≥k2r

Where: n - the number of concrete specimen groups in the same batch;

rn - the average strength of the same batch of n groups of specimens (MPa);

SN - the standard deviation (MPa) of the strength of the same batch of n group specimens, when SN", take SN;

r - concrete design strength grade (mpa);

rmin - the value of the lowest group of strength in the n group of specimens (mpa);

K1, K2 - Qualified judgment coefficient, see Appendix D.

Values in Schedule D k1, k2.

n 10-14 15-24 ≥25

When there are 10 groups of K1K2 specimens, non-statistical methods can be used to evaluate the following conditions:

rn≥rmin≥

In the measured project, when the compressive strength of cement concrete is assessed as unqualified, the corresponding sub-project is unqualified.

When conforming to the statistical method of evaluation, the concrete test block.

The strength is less than 85% of the design strength is unqualified; When the non-statistical method is evaluated, the strength of the concrete test block is less than 90% of the design strength. Regardless of any method of evaluation, the strength of the concrete test block is less than 85% of the design strength is unqualified.

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If the strength of the concrete test block is less than 100% of the design strength, it can be judged as unqualified.

C30 concrete in the test specification stipulates that the standard strength of C30 strength concrete shall not be less than 85% of 30, that is, !As long as your concrete test block is higher than the test, it is qualified.

The strength grade of concrete should be divided according to the standard value of the compressive strength of the cube, and the strength grade of the concrete is expressed by the symbol C and the standard value of the compressive strength of the cube (in n m).

The standard value of cubic compressive strength refers to a value in the overall distribution of compressive strength measured by standard test method for a cube specimen with a side length of 150 mm made and maintained according to the standard method at the age of 28 days, and the percentage of strength below this value does not exceed 5%.

The strength of concrete should be inspected and evaluated in batches, and the concrete of an acceptance batch should be composed of concrete with the same strength grade, the same age, and basically the same production process conditions and mix ratio.

For the cast-in-place concrete at the construction site, the acceptance batch should be divided according to the acceptance project of the unit project, and each acceptance project should be determined in accordance with the current national standard "Quality Inspection and Evaluation Standards for Construction and Installation Engineering".

The requirement for the test block is to meet the design strength, and it is not mentioned how much it can not 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 link. 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 C10, C15, C20, C25, C30, C35, C40, C45, C50, C55, C60, C65, C70, C75, C80, C85, C90, C95, C100, a total of 19 grades.

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.