Chemical Anchor Bonding, commonly referred to as "anchor bonding" or "seeded reinforcement," is a connection technology used in seismic reinforcement of building structures. It utilizes the locking force of structural adhesives to anchor reinforcing bars, making it the best choice for structural reinforcement and heavy-duty fastening applications. Chemical anchor bonding involves drilling holes into materials such as concrete, masonry, or rock, followed by the injection of high-strength anchor bonding adhesive (note: high-strength construction adhesives are generally divided into injection-type and drum-type). After inserting the reinforcing bars or profiles, the adhesive cures, bonding the reinforcing bars to the base material into a single unit. This is a commonly used construction technique in the reinforcement and strengthening industry.
"Reinforcement grouting" technology is a quick and effective connection and anchoring technique for concrete structures; it can accommodate both ordinary reinforcing steel and bolt-type anchoring bars. It is now widely used in the reinforcement and renovation of existing buildings, such as补救漏埋或偏位钢筋，补筋加固构件增大截面，扩大上层结构跨度或提升梁柱接长，增加房屋层高接柱，以及在高层建筑中增设剪力墙的植筋等. When using HRB335 grade steel for planting, the concrete strength grade of the original component must not be lower than C15; when using HRB400 grade steel, the concrete strength must not be lower than C20. If HPB235 grade steel is to be used, the diameter of the steel bars must not exceed 12mm, and the concrete strength grade of the original component must be no less than C20.
Chongqing Crack Grouting Application Range: Suitable for structural reinforcement, addition, transformation, and the connection of new and old concrete, such as columns, beams, floor slabs, passageways, staircases, retaining walls, continuous beams, and foundations, as well as rebar anchoring and bonding of concrete and various materials. The anchoring position can be vertical, horizontal, or at any angle, but is not applicable to structures in high-temperature conditions (>60℃) and components with concrete strength less than C20. It is advisable to conduct construction in a humid environment.
Material: Structural adhesive is a solvent-free, two-component epoxy-type high polymer that cures at room temperature after modification. Domestic structural adhesives include varieties such as "JGN," "ET," "WSJ," and "JC," while imported structural adhesives include brands like SIKADUR from France and HILTI from Switzerland. According to relevant information, the performance of structural adhesives used for anchoring must meet the following requirements:
Shear strength ≥ 18MPa, Tensile strength > 32MPa
Compressive strength > 79 MPa, Flexural strength > 30 MPa
The bonding of concrete components, whether in tensile or shear resistance, should be greater than the tensile and shear strengths of concrete. After curing, the bond exhibits excellent resistance to water, oil, and hydrocarbon wastewater, as well as good resistance to chemical erosion and aging.
Process Flow: Tension Line Positioning → Drilling → Cleaning Holes → Injecting Adhesive → Inserting Rebars → Curing and Maintenance → Pull-out Test (Random Inspection)
Operation Key Points: 1. Drilling: Select the appropriate drill rod size according to the drawings, typically 6mm larger in diameter than the anchor bar. The length of the drill rod should meet the required drilling depth, avoid rebar locations, and mark the drilling positions. Ensure the holes are correctly placed with a minimum spacing of 20 cm. The concrete component holes should be dry; if not, perform a drying treatment. Ensure absolute dryness before the bonding surface of the anchor bar and concrete hardens. Only proceed to the next step after the hole diameter, depth, and position meet acceptance standards. 2. Cleaning: After drilling, use an air compressor and a brush to remove dust from the hole to prevent isolation due to dust affecting the bonding surface. First, use the air compressor to blow several times, then use the brush to scrub the hole back and forth until all dust is removed. 3. Washing: Clean the concrete hole walls with a brush soaked in acetone to ensure good bonding with the structural adhesive. After the acetone has evaporated, promptly plug the hole opening with a paper plug to prevent contamination and await use. 4. Rust Removal: Use a wire brush or rust removal machine to clean the end of the anchor bar until the surface is basically bright and free of any suspended particles. The length of the rust removal should be greater than the anchor solid length. After rust removal, clean the anchor bar with a brush soaked in acetone and place it in a clean environment and container for use. 5. Adhesive Mixing: The optimal application temperature for structural adhesive is 15℃ to 25℃. Adjust the amount of hardener based on the temperature changes through testing. Use precise measuring tools such as balances or scales under 5 kg to weigh the adhesive first, followed by the hardener. Keep the measurement clean and avoid over-mixing to prevent the adhesive from deteriorating over time, affecting the construction and adhesive quality. Typically, the mixed structural adhesive should be used up within 30 to 40 minutes. 6. Grouting: Fill the hole with adhesive using an adhesive grouting gun or other methods, ensuring the hole is completely filled and the air is removed. Push the anchor bar into the hole, filled with structural adhesive, with force and rotate it to help remove air from the adhesive. After multiple fillings, clean any excess structural adhesive. For horizontal anchor bars, pay attention to external leakage and make repairs or use washers to block. Support the anchor bar with brackets before the anchor is solidified to prevent displacement and ensure the correct position. The completed anchor should be statically cured for 1 to 3 days, depending on the construction conditions, with a minimum of 1 day.
Quality Requirements: 1. Material inspection includes tensile strength and modulus of elasticity, calculated as the load to break (N) divided by the tensile cross-sectional area (At), denoted as tensile strength or cohesive tensile strength of the adhesive. Compression strength is determined using Φ25×30mm cylindrical specimens or 25mm×5mm×0mm cuboid specimens, with the strength being denoted as N/A, which is the compression strength or cohesive compression strength of the adhesive. Structural adhesives should have a factory certification and product inspection report upon arrival, detailing test results for all indicators. The tensile strength, modulus of elasticity, and compression strength should be re-inspected before use. 2. Anchor quality inspection includes pre-construction inspection: Prior to construction, simulate test pieces under the same conditions as designed, with at least 3 pieces for pull-out testing. Construction can only proceed upon meeting design requirements; otherwise, the adhesive type or custom design should be changed. Post-construction inspection: During construction, test pieces should be randomly selected based on the project volume, with 1/100 of the total being tested. Half of the pieces are subjected to destructive testing, while the other half are non-destructive. Each type of test should involve at least two pieces. Only upon passing the inspection can the construction be accepted; otherwise, reinforcing measures should be taken. During construction inspection: The hole depth, diameter, axis, and position must be carefully inspected. For anchor bars with excessive misalignment or reaching a certain concentration, reinforcement should be designed and added. Check the quality of the hole cleaning and the density of the adhesive filling at any time. The anchor bars must remain stationary before curing, and collision of the anchor pieces is strictly prohibited before curing, typically within 12-24 hours, depending on the curing temperature. Environmental dryness should be maintained, and construction temperature records should be kept. Anchor inspection methods: There are no specific standards in China. A calibrated hydraulic pressure gauge and jack can be used to test the anchor pieces for tensile strength, measuring the ultimate oil gauge value to calculate the tensile force of the anchor pieces and the bonding strength. The calculation formula is as follows.
Ny (Anchor拔力)
Anchoring fixture pull-out bond strength Fjm = U(Anchor bar cross-sectional circumference) × 1m(Anchor bar anchoring depth)
The anchor tool with specialized clamping tools for anchor拔试验 should have good anchoring performance, be easy to use for both insertion and removal, and be reusable.
Construction Organization: Equipment and labor are allocated based on the size of the workface and the scope of work. Boring is the main process, where one or more hammer drills can be used for concrete drilling during construction. The efficiency varies depending on factors such as hole diameter, depth, concrete strength, component location, and construction conditions. A team of two persons with one hammer drill can typically complete: 30-40 vertical holes, 20-30 horizontal holes, and 10-20 holes in beam bottoms per shift. Gluing, cleaning holes, rust removal, and anchor bolt installation require a dedicated team of 4-6 people, capable of sequential operations and unified scheduling. At least two people are needed for gluing, and at least two for inserting rebars. Structural adhesive mixing requires a specialized operation room and a simple operation desk for use.
Safety Measures: Operators performing high-altitude, electrical work, and using machinery equipment must comply with national, departmental, provincial, and municipal safety operation regulations, and pay attention to the following: 1. Operators must have received professional training and understand the operation procedures of structural adhesive anchoring components; 2. Operators must wear protective gear according to the working environment, such as safety helmets, safety belts, insulated gloves, insulated shoes, windproof masks, etc., and focus on their operations; 3. Scaffoldings used should be sturdy and reliable with protective railings around; 4. It is strictly prohibited to mix neutral lines with phase lines without adequate electrical protection devices, to avoid electric shock accidents caused by connecting phase lines with structural steel; 5. Adhesives, acetone, and other materials should be stored securely with waterproof and explosion-proof measures. After container cleaning, residual materials should be disposed of at designated locations; 6. The operation environment should be well-ventilated with sufficient lighting.
