The concrete strength grade does not meet the design requirements for the beam and plate structure

The main reason is: the strength of the concrete standard curing test block or on-site testing is assessed according to the specification standard to meet the design requirements.

1) The material of the raw materials used in the configuration of concrete does not meet the provisions of the national standard.

2) When mixing concrete, there is no concrete mix test report provided by the statutory testing unit, or the mix ratio is wrong in operation.

3) When mixing concrete, the feeding material is not measured according to the mass ratio, or the measurement is wrong.

4) Concrete mixing, transportation, pouring, and curing do not meet the requirements of the specification.

The prevention and control measures are:

1) The cement, coarse (fine) aggregates and admixtures used in mixing concrete must meet the relevant standards.

2) It must be prepared according to the concrete mix test report issued by the statutory testing unit.

3) The prepared concrete must be measured and fed according to the mass ratio, and the measurement should be accurate.

4) Concrete mixing must be mechanically stirred, and the feeding sequence is coarse aggregate - cement - fine aggregate - water, and the mixing time is strictly controlled.

5) The transportation and pouring of concrete must be carried out before the initial setting of concrete.

6) Control the pouring and vibration quality of concrete.

7) Control the curing of concrete.

8) When the concrete strength is low and can not meet the requirements, the safety of the structure can be checked according to the actual strength, and the relevant design unit studies and proposes a treatment plan, such as postponing the time to bear the load, reducing the load value or taking measures such as reinforcement.

Judging from your description, the construction area of each floor should be more than 300 square meters, the size of the column grid should be 5-6 meters, and the cross-sectional height of the beam should not exceed 500 or 600.

If only the concrete strength of the 2-story floor slab and 1-story roof beam is not enough, it can be reinforced (the column concrete is fine, right?). There are generally two ways to deal with it: carbon fiber reinforcement and adhesive steel reinforcement.

I have done a project before, high-rise buildings, C50 concrete, the measured strength is only C30, it is a mixture of bonded steel and carbon fiber, the column is made of bonded steel, the beam is bonded steel in the compression area, and the carbon fiber is pasted in the tension area.

The reinforcement scheme can only be issued by the design institute, and it needs to be calculated to see whether the reinforcement scheme meets the requirements. It is recommended that you look for a designer, and it is best to be the one that designed the structure at the beginning, they have a calculation book, and they also have a model, so they know more about the structure.

You really don't meet the standard, and it must be a quality accident when you get it, and it's very difficult to get it.

The concrete strength above C15 can be reinforced with carbon fiber, and it cannot be used below C15; Only in this way, after repairing the cavity and then carbon fiber reinforcement, if the floor slab has holes, it is best to use grouting resin to seal the holes, cracks or something, and the reinforcement has 12 150,000 can be used.

Hope your house goes well.

C15 can not meet the durability requirements of concrete at all, and it may be possible to use the steel bonding method or the method of directly increasing the beam section for reinforcement.

Find a professional reinforcement company, it is estimated that steel beams will be added under the beam plate.

1. The concrete strength of the beam, plate and column is not the same, and the method of pouring the concrete of the column wall and the node concrete of the column and beam should be used first, and then the method of pouring and pounding the concrete of the beam plate should be adopted.

2. Beam and slab refers to the reinforced concrete slab that is integrated by beams and slabs, which includes beam-plate ribbed slabs and tic-tac-toe ribbed slabs, and the engineering quantity is calculated according to the sum of the volume of beams and slabs.

3. The column is the vertical main structural part of the building, supporting the weight of the object above it. In Chinese timber construction, beams and columns are responsible for supporting the weight of the beam frame structure and other parts, such as eaves, and there is often a column base between the main column and the foundation. In addition, there are other smaller columns, which are not placed on the foundation, but on the beam frame to support the weight of the objects above, and then transfer the weight to the main column through the beam frame structure.

For example, the ridge melon column or Shu column is the weight of the eaves that supports part of the beam frame.

4. The strength grade of concrete refers to the compressive strength of 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).

When the strength of the beam-column concrete is different, the oblique steel plate mesh should be left as shown in the figure to block the concrete of different strengths, and the slope should be 45°, and the high-grade concrete of the beam-column node should be poured first, and the low-strength concrete should be poured after the vibration is sufficient.

The node area of the column is considered as the reinforced concrete reinforcement area (belt) to organize the construction

1. Use steel wire mesh to block along the perimeter of the strength strengthening area; If necessary, multi-layer boards can be used as temporary construction joints;

2.First, use the slurry method to pour the beam and slab according to the set pouring sequence (the area with low pouring strength grade);

3. Then remove the area with high strength of the multi-layer plate pouring node area, and directly carry out the pouring construction if only the steel wire mesh is set;

4. If the concrete at the boundary has been initially set due to the long pouring interval, the concrete ratio minus stone concrete (concrete with high strength) is used for wetting;

5. The most important thing is that concrete with high strength must use anti-shrinkage and expansion concrete.

Analysis of the main reasons:

The water-cement ratio is not strictly controlled in strict accordance with the scientific concrete construction requirements, when the same kind of cement is used, the concrete strength grade mainly depends on the water-cement ratio, and the combined water required when the cement is hydrated, generally only accounts for about 25% of the cement weight, but in order to facilitate mixing and vibration, the concrete should have a certain fluidity, more water is needed in the construction, and when the concrete is hardened, the excess water remains in the concrete to form a blister or form a porosity after evaporation, which greatly reduces the actual effective area of the concrete resistance loadand may create stress around the pores. And the larger the water-cement ratio, the lower the bonding between the cement slurry and the aggregate, so the larger the water-cement ratio in the concrete, the lower the strength. If water is added at will for the convenience of construction, or although there is a mix ratio design, but due to the high moisture content of the sand and stone on site, the construction mix ratio does not deduct the moisture of the aggregate, and the water-cement ratio in the concrete is increased, which will cause the concrete strength to be seriously insufficient;

The workability is not good, the concrete mixing is uneven, and the vibration is not compact. Although the small water-cement ratio in concrete can theoretically obtain higher concrete strength, the water-cement ratio is bound to affect the workability of concrete, so that the concrete mixture is not easy to vibrate and compact, and will also affect the strength of concrete;

The selection of raw materials does not meet the requirements during concrete construction: the strength of cement concrete is mainly due to the result of cement hardening, whether the cement varieties used meet the requirements and whether they are damp, and whether the cement storage time has an important impact on the strength of concrete; Aggregate, sand and stone aggregate play a skeleton role in concrete, and if its quality does not meet the requirements, it is difficult to prepare concrete with high strength; The quality of the mixing water will have an impact on the strength of the concrete;

Under the influence of low temperature, the strength growth of concrete is closely related to the temperature during the curing period. When the temperature is below freezing, hydration basically stops; When the air temperature is lower than -3, the water in the concrete freezes, and the volume of the water expands nearly 9% when it freezes, so that the concrete has the danger of being expanded and cracked, and the strength of the concrete is reduced;

The sampling of concrete test blocks is not representative, the test blocks are not made according to the regulations, the test blocks are not vibrated and compacted, or the pouring temperature is too low; Poor maintenance management of the test block or maintenance conditions that do not meet the requirements;

Improper construction methods, such as inaccurate measurement in construction, reversal of concrete feeding sequence, insufficient mixing time and other factors will cause the concrete strength to fail to meet the design requirements.

Main precautions:

Strictly control the concrete mix ratio, focus on the water-cement ratio, and control the amount of cement and mixed water;

Ensure that the raw materials used in concrete construction meet the requirements of the specification, use the corresponding varieties and grades of cement that meet the construction requirements, and the construction party with conditions for various raw materials should be sent for inspection and inspection to ensure that the quality meets the requirements;

Standardize the construction, feed in order, strengthen the mixing and vibration during the construction, and the mixing time should be reasonably determined according to the slump of the concrete and the capacity of the mixer to ensure the uniformity and compactness of the concrete;

Pay attention to curing to ensure the curing temperature and cement hydration rate; Standardize the test block inspection of concrete to ensure the representativeness and accuracy of the test.

Find a design institute to come up with a reinforcement plan, and find a concrete company to claim compensation.