1. Surface rust: there is yellow floating rust on the surface of steel bar, which turns red seriously, turns dark brown after a long time, and even scales peel off.

Causes: poor storage, rain and snow erosion, long storage period, humid warehouse environment and poor ventilation.

Preventive and control measures:

(1) Steel raw materials should be stored in warehouses or sheds, and the ground should be kept dry. Steel bars should not be directly stacked on the ground, and drainage measures should be taken around the site to shorten the stacking period as much as possible. Light yellow and slight floating rust do not need to be treated.

(2) The reddish-brown rust spots can be removed by manual steel brush, and mechanical methods should be adopted as far as possible. For serious corrosion and peeling of rust, it is necessary to study whether to degrade the use.

2. Mixed use: the varieties and grades of steel bars are mixed, and the steel bars with different diameters are piled together, which is difficult to distinguish and affects the use. Especially secondary steel and tertiary steel.

Reasons: improper management of raw material warehouse and lax system; If the diameters are similar, they can sometimes be distinguished by visual inspection; The technical proof materials were not sent to the warehouse together with the physical reinforcement.

Preventive and control measures:

(1) The stacking of raw materials and semi-finished products shall indicate the materials and specifications.

(2) Carefully check the materials and specifications before blanking, especially the secondary steel and tertiary steel.

Second, the reinforced mechanical experiment

Phenomenon and reason: the strength and joint experiment of steel bar raw materials are not standardized: the batch number and quantity of steel bar materials are inconsistent with the experimental report, and the engineering parts are not detailed. Mechanical experiments were not carried out in batches according to the requirements of the specification.

Preventive and control measures:

Raw materials: 2 pieces in each group for tensile test, about 500mm long. 350 mm. The same factory, the same heat number, the same specification and the same delivery status, every 60t is an acceptance batch, and less than 60t is counted as a batch. (Round steel bar specimens are taken from different plates, and any two or more straight steel bars are intercepted).

Flash welded joints: 300 welded joints of steel bars of the same grade and diameter completed by the same welder in the same machine shift shall be regarded as a batch. Samples Six samples were randomly cut from the finished product. Three of them are about 500mm long in tensile test and 350mm long in cold bending test.

Arc welding joint: engineering welding conditions: 300 joints of the same joint type test and the same steel grade are accepted as a batch. On-site conditions: For the same joint type test, 300 joints on each floor of the same steel grade are regarded as an acceptance batch, and less than 300 joints are also counted as a batch. Samples Three samples with a length of about 500mm were randomly cut from the finished product for tensile test.

Pneumatic welded joints: 300 joints of the same steel grade on each floor or construction section are regarded as an acceptance batch, and less than 300 joints are counted as a batch. Specimen Three specimens were randomly cut from the finished product for tensile test, with a length of about 500mm. On-site inspection of reinforced mechanical connection joints shall be carried out according to the acceptance batch. Under the same construction conditions, joints of the same grade, type and specification of the same batch of materials shall be used, with 500 joints as an acceptance batch for inspection and pre-acceptance, and less than 500 joints as an acceptance batch. For each acceptance batch of joints, three joint specimens must be randomly intercepted in the project for tensile strength test.

Third, the protection of finished steel products

1. After the thread of straight thread at the end of steel bar is processed, the thread is not effectively protected.

Precautionary measures: After the straight thread thread at the end of steel bar is processed, put on a plastic cap to protect the thread.

2. The reserved steel bars in post-cast strip and construction joints have been put on hold for a long time, without rust protection.

Preventive and control measures:

Requirements: If the reserved reinforcement in the post-pouring belt, construction joint and other parts is left for more than 3 months, the reserved reinforcement must be rusted (brushed with cement slurry).

Four, steel processing

1, reinforcement hook length is not enough.

Reason:

(1) The length of steel bar blanking is not enough.

(2) There are deviations in the processing machinery.

(3) labor saving and convenient installation.

Preventive and control measures:

(1) Carefully check the drawings, be familiar with the specification requirements, and accurately calculate the ingredient list.

(2) Batch processing shall be carried out after the actual lofting is verified.

(3) Check the construction machinery and correct the deviation.

(4) Like an S-shaped tractor, manually bend it back to 1350 after installation. (as shown in figure 2).

2, stirrup hook length is not enough, the angle is less than 1350.

Causes and preventive measures:

Allowable deviation of reinforcement processing

(1) Bending angle of stirrup hook: For general structures, it should not be less than 900; Structures with seismic requirements should be1350;

(2) The length of straight part of stirrup after bending: For general members, it should not be less than 5 times of stirrup diameter, and for structures with seismic requirements, it should not be less than 10 times of stirrup diameter.

3. Straighten the steel bar of the threaded disc. The alloy top block in the machine is too tight, which leads to the damage of the steel rib.

Reason:

The steel bar in the threaded disc is straightened, and the alloy top block in the machine is too tight, which leads to the damage of the steel rib.

Preventive and control measures:

Straighten the rebar in the threaded disc and adjust the alloy top block in the machine according to the rebar specification. Ensure that the reinforcement can be straightened, and the reinforcement ribs shall not be damaged, and cold drawing is not allowed to reduce weight.

The above are collected and sorted by Zhong Da Consulting Company.

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