Technical introduction
Planting bar technology is a simple and effective connection and anchorage technology for concrete structures. Ordinary steel bars can be implanted, and bolt anchor bars can also be implanted; Now it has been widely used in the reinforcement and reconstruction projects of existing buildings, such as: the remedy of missing buried steel bars or steel bars deviating from the design position during construction, the reinforcement of stressed members by increasing cross section, the extension of superstructure span, the connection of beams and columns by jacking method, and the planting of shear walls in high-rise buildings.
1, the concrete strength grade of the original member should be determined according to the field test results when the concrete structure is strengthened by planting reinforcement.
When HRB335 steel bar is used for planting, the concrete strength grade of the original member should not be lower than C15; ; When HRB400 grade steel bars are used for planting, the concrete of the original members shall not be lower than C20.
Note: If reinforcement is needed, the diameter of reinforcement shall not be greater than 12mm, and the strength grade of original concrete shall not be lower than C20.
technology standard
China's Technical Specification for Post-Anchorage of Concrete Structures (JGJ 145-20 13) clearly stipulates the relevant requirements and parameters of reinforcement.
process flow
(1) pouring technology of concrete beam: elastic line positioning → drilling → hole washing → glue injection → rebar planting → curing → pull-out test (sampling) → binding rebar and pouring concrete.
(2) Brick masonry technology: elastic line positioning → drilling → hole washing → glue injection → rebar planting → curing and curing → pull-out test (sampling inspection) → brick masonry construction.
Construction operation
Elastic line positioning
According to the position and quantity of steel bars in the design drawing, stagger the position of original structural steel bars and mark the position of planting steel bars. After passing the test, please ask the relevant departments to check the line and drill holes.
bit
Drill a hole with an impact drill. The diameter of the drill should be about 5 mm larger than the diameter of the steel bar. The rebar shall be φ25 rebar produced by Shougang, and the drill bit shall be φ30 alloy steel drill bit. The hole depth is 15d(375mm), and the actual drilling depth is 400 mm. When drilling, the drill bit is always vertical to the cylinder.
cleanout
Hole washing is the most important link in steel bar planting, because there will be a lot of ash in the hole after drilling, which directly affects the quality of steel bar planting, so it is necessary to clean the impurities in the hole. The method is: cover the telescopic rod with a brush, reach to the bottom of the hole, twitch back and forth repeatedly, take out the dust and sundries, and then blow out the floating dust in the hole with compressed air. After blowing, wipe the inner wall of the hole with absorbent cotton dipped in alcohol or acetone. But you can't scrub with water, because alcohol and acetone are volatile and water is not. After scrubbing with water, the hole will not dry quickly. After borehole cleaning, please design and other relevant units for acceptance, and glue injection can be carried out only after it is qualified.
Glue injection
Take a group of strong rebar-planting glue, put it into a sleeve, put it on a special manual syringe, slowly pull the trigger to discharge the thinner glue at the platinum package, then put the spiral mixing nozzle into the bottom of the hole. If the length is not enough, it can be lengthened with a plastic pipe, then pull the trigger, and the trigger hole moves the syringe back once to discharge the air in the hole. In order to make the glue in the hole full and not flow out after the steel bar is implanted, the glue injection in the hole can reach 80%. After the hole is filled with glue, steel bars should be planted immediately. operate
Before glue injection, the formwork at the bottom of the beam has been set up, which is convenient for steel bar positioning after steel bar planting. Before rebar planting, brush the implanted part of rebar repeatedly with a wire brush to remove rust, and then clean it with alcohol or acetone. Immediately after injecting glue into the hole, put the derusting steel bar into the hole, and then screw it in slowly in one direction until the steel bar reaches the bottom of the hole, and don't reverse halfway.
Curing and curing
After the steel bar is implanted, it should be positioned on the beam bottom template, and the steel bar should not be vibrated before the strong steel bar glue is completely cured.
The strong reinforcing glue can be cured at room temperature, and the next working procedure can be carried out after 50 hours.
Detection test
Before the rebar planting construction, the on-site pull-out test should be conducted for the rebar and rebar planting glue to determine whether the rebar and rebar planting glue meet the design requirements.
The method is as follows: make concrete specimens with the same strength grade as the concrete members to be reinforced, implant three groups of steel bars according to the reinforcement planting steps, and carry out pull-out test after the steel bar glue is completely solidified. When the applied force reaches the yield strength of secondary steel bar (450N/mm2), the special steel bar dynamometer appears necking and then breaks.
The force exerted by the dynamometer on the fixture during the test shall conform to FC≥FYK(FC: force exerted by the dynamometer, n/mm2; FYK: yield strength of reinforcement, N/mm2)
The test shows that the strength of adhesive for planting steel bars is greater than the yield strength of steel bars, and the failure of planting steel bars is the yield failure of steel bars, not the failure of adhesive, which shows that both steel bars and adhesive are qualified.
Non-destructive pull-out test shall be conducted after rebar planting to detect the quality of rebar planting in working condition, and the number of tests shall be 10% of the total rebar planting.
In the test, the force exerted by dynamometer is less than the yield strength of steel bar and greater than the designed anchorage force provided by design department. The formula is FM
After the test experiment is qualified, the next process can be carried out.
[Title 2] Binding tendon
Matters needing attention
1. After rebar planting, it is generally not allowed to weld on the rebar planted. If welding is really necessary, the distance between the welding spot and the concrete surface of the base material should be greater than 15d, and the exposed root of the steel bar should be wrapped with a towel soaked in ice water.
2. The cofferdam of the bearing platform must be firm, so as to ensure that no water flows into the bearing platform when planting reinforcement, and keep the bearing platform dry. If the bottle cap can't be guaranteed to be dry, then this scheme is not feasible.
3, pay attention to the weather changes, check the weather forecast before planting steel bar construction, to ensure good weather conditions during planting steel bar construction, don't construction in rainy days.
4, steel must be derusted as required, steel surface can't have oil stains and other sundry.
5. Anchorage glue for planting steel bars must be qualified products, and all performance indexes should meet the specification requirements.
6. In order to ensure the quality of steel bar planting, it is necessary to avoid the occurrence of various factors that affect the quality defects of steel bar planting mentioned in Article 4. It is necessary to comprehensively consider work, materials, machinery, technology, environment and methods to be foolproof.
7, planting steel construction electricity should comply with the provisions of the project, to avoid illegal operation.
8. Equipment and machines used for rebar planting must be operated in accordance with the operating procedures for finding equipment or machines, and illegal operation is not allowed.
9. Don't throw the materials used for rebar planting, which will pollute the environment.