1. Construction process
1) Positioning
The drilling position and model shall be marked according to the design requirements. If there is stressed reinforcement on the base material, the drilling position can be adjusted appropriately, but it should be planted inside the distribution reinforcement of the shear wall. Drill anti-skid holes. Drill small holes with chisels at the marked points of planting reinforcement to prevent the drill from sliding and misplacing during drilling.
2) Drilling
The drilling type is impact drill. Generally, the drilling shall be perpendicular to the plane of the concrete member, with a slope of no more than 8 degrees (except that there is no operation space or special requirements due to being too close to the floor). The drilling depth is 15d (d is the diameter of the reinforcement). The drilling progress should not be too fast, so as to avoid the heat of drilling head affecting the strength of concrete around the drilling. When drilling, if the main reinforcement or stirrup in the original structure needs to be displaced and avoided, it can only be displaced after being approved by the supervisor and the designer.
3) Hole cleaning
Remove the dust in the hole. During the drilling process, there will be ash residues in the hole. Especially when drilling downward, the ash residues are not easy to escape. The ash residues should be removed frequently, otherwise the drill will be burned and the drill bit will be burned. After drilling, check the hole depth and hole diameter, blow out the dust in the hole with compressed air, then brush the hole wall with a brush, blow the hole with compressed air again, and repeat for 3-5 times until there is no dust and debris in the hole. Before glue filling, the wall of hole should be free of dust, oil and organic impurities.
4) Reinforcement treatment
The length of reinforcement shall be determined according to the design requirements of the drawings. If the reinforcement is welded externally, the reinforcement should be welded first and then planted. If it is difficult and must be welded later, the distance between the welding point and the base concrete surface should be more than 15d (d is the diameter of the reinforcement). The root of the exposed part of the planted reinforcement should be wrapped with a wet towel soaked in ice water, that is, the minimum length of the planted reinforcement to be welded later is: hole depth + welding length + 15d, so as to avoid the high temperature affecting the strength of the adhesive during welding. For surface treatment of reinforcement, use electric steel wire or manual steel wire brush to remove rust on the surface of reinforcement, and use acetone or alcohol to remove oil stain and dust on the surface of reinforcement.
5) Preparation of anchoring adhesive
The rebar planting glue is barrel type rebar planting glue, and mechanical mixing should be adopted. The agitator can be composed of an electric hammer and mixing teeth, and the mixing teeth can be welded in a cross shape at the end of an electric hammer drill bit Φ 14 steel bars. A small amount can be manually mixed with thin steel bars. Take a clean container (plastic or metal basin, free of oil, water and impurities) and a weighing scale, mix them according to the mix ratio, and use a stirrer to stir for about 10 minutes until they are mixed evenly. It is better to stir in the same direction to avoid air bubbles. The glue should be prepared and used on site, and the amount of glue should not be more than 5kg each time.
6) Embedded reinforcement
After the rebar planting glue is prepared according to the design requirements, manually feed the glue to 2 / 3 of the depth of the hole. Place the treated reinforcement into the hole filled with structural adhesive. Manual insertion method: when the reinforcement is inserted into the hole, because the structural adhesive has a certain concentration, it cannot be inserted to the end at one time. The method of repeatedly pulling, inserting or rotating until the reinforcement is inserted into the bottom of the eye (note that sometimes there will be rebound after the reinforcement is inserted to the end, which should be prevented). Reinforcement positioning in the center: since the diameter of the drilling hole is larger than the diameter of the implanted reinforcement, the implanted reinforcement may not be in the center. Stones are used to support and position the opening of the hole, and then hard glue is used to close the hole to fix it and prevent the glue in the hole from flowing out of the hole.
7) Solidifying and protection
The solidifying time refers to the hardening time of the structural adhesive, but the strength of the adhesive only reaches 40% – 60% of the design strength. When the temperature is below 20 ℃, it takes about 48 hours to reach the design strength. Therefore, it is generally required to anchor the reinforcement with structural adhesive. After the construction is completed, it generally takes 48 hours according to the ambient temperature before the reinforcement can be stressed. Before the structural adhesive is cured, the anchor bar shall be protected. It is not allowed to sway and collide with the anchor bar, and special personnel shall be assigned to protect it on site.
8) Quality inspection
Measure the length of exposed reinforcement in the borehole and determine the depth of embedded reinforcement (detailed site records). Measure whether the position, model, diameter and specification of planted reinforcement are correct (make records). Pull out test shall be carried out and the test results shall be identified and approved by the supervising engineer. The allowable deviation of embedded reinforcement depth is + 20mm, and the allowable deviation of verticality is 5 °.
Post time: Sep-04-2022