Common quality problems and control of steel bar projects

1. Surface corrosion: Yellow floating rust appears on the surface of the steel bars, which turns to red in severe cases. After a long time, it turns into dark brown, and even fish scales may peel off.

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

Preventive and control measures:

(1) Steel bar raw materials should be stored in warehouses or sheds to keep the ground dry. Steel bars must not be stacked directly on the ground. Drainage measures must be provided around the site. period as short as possible. Light yellow and slight floating rust does not need to be treated.

(2) The reddish-brown rust spots can be removed with a manual steel brush, and mechanical methods should be used as much as possible. For serious rust and peeling off of rust, it should be studied whether to downgrade the use or not use it.

2. Mixed materials: The types and grades of steel bars are mixed, and steel bars with different diameters are stacked together, making it difficult to distinguish and affecting use. Especially secondary and tertiary steel.

Reasons: Improper management of the raw material warehouse and lax system; similar diameters can sometimes be distinguished by visual inspection; technical certification documents were not delivered to the warehouse at the same time as the physical steel bars.

Preventive and control measures:

(1) The materials and specifications of raw material stacking and processed semi-finished products should be indicated.

(2) Carefully check the material and specifications before blanking and processing, especially grade 2 steel and grade 3 steel.

3. Steel bar mechanics experiment

Phenomena and reasons: The steel bar raw material strength and joint science experiments are not standardized: the single batch number and quantity of the steel bar material do not match the experimental report sheet, and the engineering location is inconsistent. detailed. Failure to conduct mechanical experiments in batches as required by the specification.

Preventive and control measures:

(1) Raw materials: In the tensile test, each group of 2 pieces is about 500mm long. 350mm. For the same factory, the same furnace number, the same specifications, and the same delivery status, every 60t is considered an acceptance batch, and any quantity less than 60t is also counted as one batch. (Circular steel bar specimens are taken from two or more optional steel bars of different disks and straight bars).

(2) Flash welding joints: 300 steel bar welding joints of the same grade and diameter completed by the same welder in the same shift should be considered as one batch. Test pieces: 6 test pieces are randomly cut from the finished product. Three of them were about 500mm long in the tensile test, and two were about 350mm long in the cold bending test.

(3) Arc welding joints: Engineering welding conditions: 300 joints of the same joint type test and the same steel bar grade are one acceptance batch. Under on-site conditions: 300 joints of the same joint type test and the same steel bar grade for each to two floors are considered as one acceptance batch, and those with less than 300 joints are also counted as one batch. The test pieces were randomly cut from the finished products for tensile testing. Three test pieces were about 500mm long.

(4) Electroslag pressure welding joints: 300 joints of the same steel bar level in each floor or construction section are In an acceptance batch, less than 300 joints will be counted as one batch. Test pieces: Randomly cut 3 test pieces from the finished product for tensile testing, about 500mm long.

(5) Air pressure welding joints: 300 joints of the same steel bar grade in each floor or construction section are considered an acceptance batch, and less than 300 joints are also counted as one batch. The test pieces are randomly cut out from the finished products for tensile testing. Three test pieces are about 500mm long.

(6) Connection joints: The on-site inspection of the mechanical connection joints of steel bars is carried out according to the acceptance batch. Under the same construction conditions, joints of the same grade, type, and specifications from the same batch of materials will be used. An acceptance batch of 500 pieces will be used for inspection and pre-acceptance. Less than 500 pieces will also be treated as an acceptance batch. For each acceptance batch of joints, three joint specimens must be randomly intercepted during the project for tensile strength testing.

Extended information:

When the mechanical connection of third-level steel bars is connected by sleeve stripping, are there any standards that require that after tightening the sleeve, the wire in the sleeve should not be less than 10 buckles, 1~1.5 buckles are allowed to be exposed on the outer steel bar of the sleeve.

When tying the steel bars, tie the knot inward and press the tail wire inward. Some measures to prevent common quality problems in steel bar projects:

(1) Positioning measures for steel bars and control of concrete and protective layers of steel bars.

(2) Requirements for earthquake resistance.

(3) Joint setting and joint quality of steel bars.

(4) The appearance quality of steel bar installation should be horizontal and vertical, with uniform spacing.

Baidu Encyclopedia - Practical techniques for prevention and control of common quality problems in construction projects

Weipu.com - A brief discussion on the control of common quality problems in steel bar projects

People's Daily Online - Carrying out residential project quality in Dalian Activities for the Year of Prevention and Control of Common Diseases