How should the concrete curing test block and impermeability test block under the same conditions be

The number of retention specimens under the same conditions of the same strength grade should not be less than 10 groups, so as to constitute the basic conditions for evaluating the strength of concrete according to statistical methods; The number of liens should not be less than 3 groups, so that they are sufficiently representative when assessing the strength of concrete according to non-statistical methods.

Specific requirements for the indwelling of the impermeable test block:

The impermeability of waterproof concrete should be evaluated by the test results of cured concrete impermeability specimens under standard conditions. The specimen should be made at the pouring site. A group of impermeable specimens (one group of 6 impermeable specimens) should be retained for every 500 m3 of continuously poured concrete, and each project shall not be less than two groups.

For impermeability specimens using ready-mixed concrete, the number of retention groups should depend on the scale and requirements of the structure. The impermeability test should comply with the relevant provisions of the current "Test Method for Long-term Performance and Durability of Ordinary Concrete" GBJ 82.

The main technical nature.

The properties of concrete include workability of concrete mixture, concrete strength, deformation and durability.

Workability, also known as workability, refers to the fact that the concrete mixture is convenient for the operation of various construction processes under certain construction conditions, so as to ensure the performance of obtaining uniform and dense concrete. Workability is a comprehensive technical index, including three main aspects: fluidity (consistency), cohesion and water retention.

Strength is the main mechanical property of concrete after hardening, which reflects the quantified ability of concrete to resist loads. Concrete strength includes compressive, tensile and shear strength, bending resistance, flexural resistance and grip strength. Among them, the compressive strength is the largest, and the tensile strength is the smallest.

The deformation of concrete includes deformation under non-load and deformation under load. The deformation under non-load action includes chemical shrinkage, dry and wet deformation, and temperature deformation. If the amount of cement is too much, it is easy to produce chemical shrinkage and cause microcracks in the concrete.

Concrete durability refers to the ability of concrete to resist various damaging factors and maintain its strength and appearance integrity for a long time under actual use conditions. Including frost resistance, impermeability, corrosion resistance and carbonization resistance of concrete.

"Code for Acceptance of Construction Quality of Concrete Structure Engineering" GB50204, the paragraph has clear provisions. p31"For concrete structures with impermeability requirements, the concrete specimens should be randomly sampled at the pouring site. For the same project and the same mix ratio of concrete, sampling should not be less than once, and the number of retention groups can be determined according to actual needs.

In addition, the specification explains: "Since the difference between the anti-mixing concrete with the same mix ratio is not large due to construction, it is stipulated that the concrete structure with impermeability requirements shall be sampled not less than once according to the same project and the same mix ratio." Due to the many factors affecting the test results, several sets of specimens can be left in place when necessary. ”

Impermeable concrete test block It also has a mold of the finished product, just a cylindrical kind, on the spot sampling when pouring concrete, 5 groups of concrete of different labels, let it be put in the standard room for maintenance for 28 days! That's what you do on the jobsite!

1. When the amount of concrete continuously poured is less than 500 cubic meters, two groups (12 pieces) of impermeability test blocks should be retained.

2. For every 250 500 cubic meters of concrete added to the slow coarseness, two groups (12 pieces) of impermeability test blocks should be added.

3. If there is a change in the use of materials, mix ratio or construction method, it shall be retained in accordance with the above provisions.

4. The impermeability test block should be made at the pouring site, one of the two groups of test blocks (6 pieces) should be cured in the standard curing room, and the other group (6 pieces) should be cured under the same conditions as the site, and the curing period shall not be less than 28 days.

Differences: 1. Different definitions:

The standard culture test block is the test block that is maintained in the standard culture room. The specification stipulates that the specimen shall be maintained for 28 days in the standard maintenance room with a humidity of more than 90% in (20 3).

The homotrophic test block refers to the specimen Hengyu Town sampled at the concrete pouring site, and is cured according to the maintenance conditions of the on-site structural destruction entity (i.e., placed near the component for curing), and the compressive strength value of the test block under this condition can better reflect the concrete strength of the structural entity. The cumulative curing temperature is generally from the beginning of the curing, to the daily average outdoor temperature accumulated to 600 degrees after the start of the pressure test, but when the temperature in the construction area is special, it should also be ensured that the curing time can not be less than 14d, can not be higher than 60d.

2. The objects are different:

For concrete inspection batches, each inspection batch should be retained at least one group;

For the intensity level, the number of retention positions for each intensity level is determined according to the needs, and it is generally best to have the same number as the standard retention level.

3. Different roles:

For acceptance, after all the test block results come out, they must be evaluated, and the evaluation results must be qualified, otherwise the structure will be tested;

Sampling re-inspection, generally used for structural measurement, homotrophic qualified, in the structure testing can do a few points less (that is, less rebound, even without structural testing).

4. Different sampling methods and proportions

Each inspection batch is generally to be retained, on-site stirring, the same strength grade, the same mix ratio, the same production process of each sampling unit (that is, when the following conditions should be retained in a group) should meet the following requirements:

a. Make 100 trays per mix, but not more than 100m3.

b. According to each workbench shift.

c. Each cast-in-place floor.

d. When the amount of continuous pouring concrete is greater than 1000m3, it is calculated every 200m3. If the commercial concrete is used: the concrete used for delivery inspection is 100m3, and the concrete mixed in a workbench shift is less than 100m3 according to each workbench shift.

When the amount of continuous ** concrete is greater than 1000m3, it is calculated every 200m3.

According to the same strength level of retention, the same strength of the same condition of curing specimens, the number of retention should be determined according to the amount and importance of concrete engineering, should not be less than 10 groups, and should not be less than 3 groups, important parts (beams, plates and columns in the main body) such as generally can be retained as standard maintenance.

5. Maintenance is different

The maintenance environment of the concrete standard culture test block is (20 3), the humidity is more than 90%, and the standard maintenance room is generally built on the construction site, or sent to the standard maintenance room of the laboratory immediately after the mold is removed.

The test block under the same conditions must be placed near the representative part for protection.

6. The conditions for inspection are different

The age of the standard culture test block is 28 days, and the age cannot be exceeded.

The age of the homotrophic test block is generally 14-60 days, that is, the equivalent maintenance age can be taken according to the daily average temperature when the cumulative age reaches 600 ° day by day, and the age period of 0 °C and below is not counted; The equivalent maintenance period should not be less than 14 days and should not be greater than 60 days.

Specification for indwelling of concrete specimens under the same conditions:

1. The number of retention specimens of the same strength grade and the same condition should be determined according to the quantity and importance of concrete engineering, and should not be less than 10 groups and not less than 3 groups, of which each floor should not be less than 1 group.

2. The retention of the curing specimens under the same conditions should be evenly distributed in the construction period of the project, and the amount of concrete poured between the two groups of specimens shall not be greater than 1000m.

3. After the mold removal of the curing specimen under the same conditions, it should be placed in an appropriate position close to the corresponding structural component or structural part, and the same maintenance method should be adopted.

Fabrication of mortar test blocks.

1. When making the masonry mortar test block, the bottomless test mold is placed on the ordinary clay brick covered with a layer of wet paper with good water absorption (the water absorption rate of the brick is not less than 10%, and the moisture content is not more than 20%), and the inner wall of the test mold is coated with a thin layer of engine oil or release agent in advance. Wet deficit paper should be fresh paper. The use surface of bricks is required to be flat, and the four vertical surfaces of bricks are not allowed to be used if they are glued to cement or other cementitious materials.

2. Fill the mortar into the mold test at one time, and use the tamper to evenly insert it 25 times from the outside to the inside according to the spiral direction, in order to prevent the low-consistency mortar from leaving holes after inserting and bending, it is allowed to insert the putty knife along the mold wall several times, so that the mortar is 6 8mm higher than the top surface of the mold. When the surface of the mortar begins to appear in a state of pitting (about 15 30min), the raised mortar is cut and smoothed along the top surface of the test mold.

3. After the test block is made, it should be stopped in the temperature environment of 20 5 for a day (24 2h), when the temperature is low, the time can be appropriately extended, but it should not exceed two days and nights, and then the number is dismantled. After the mold is removed, it should be cured to 28d under standard curing conditions, and then the pressure test should be carried out.