Chemical anchor anchoring technology belongs to post-reinforcement technology. In recent years, in building renovation, changes in building use, or the reconstruction and expansion of existing buildings, chemical anchor anchoring construction, as a new, simple and effective post-fixing method, has been widely used in construction.

　　1. Composition of chemical anchors (see Figure 1)

　　Chemical anchors consist of a chemical adhesive cartridge, a threaded rod, a washer, and a nut.

　　The threaded rod, washer, and nut (hexagonal) are generally available in galvanized steel and stainless steel (hot-dip galvanized is also available upon request).

　　The chemical adhesive cartridge (or plastic-packaged resin capsule) contains reactive resin, hardener, and quartz granules.

　　2. Relevant parameters of chemical anchors

　　Drilling depth: The required drilling depth is determined by the type and size of the anchor. With few exceptions, it is generally always greater than the anchoring depth. When drilling, control of the drilling depth is particularly important. If a drilling machine that automatically ensures the hole depth and matches the corresponding manufacturer's anchor is used (for example, the German fischer anchor has a matching high-tech cylindrical-conical universal drill bit FZUB), drilling becomes very convenient.

　　Anchoring depth: The distance from the surface of the anchoring base structure to the bottom end of the threaded rod, which is an important parameter affecting its load-bearing capacity, see Figure 2.

　　Anchoring thickness: The anchoring thickness equals the thickness of the object being anchored. If the anchoring base is covered with at least plaster or tiles and an insulation layer, the anchoring thickness is at least equal to the thickness of the plaster or tiles and insulation layer plus the thickness of the object being anchored, see Figure 2.

　　Edge distance: Refers to the distance from the anchor axis to the free edge of the component.

　　Spacing: Refers to the distance between the axes of adjacent anchors.

　　Component thickness: Refers to the thickness of the anchoring base.

　　In order to maximize the load-bearing capacity of an anchor, certain spacing, edge distance, and component thickness must be ensured. The data are generally based on the technical parameters provided by the manufacturer.

　　II. Scope of Application

　　1. Suitable for ordinary concrete with strength grade not less than C15 (uncracked concrete) and dense natural stone.

　　2. Used for fixing ordinary steel structures, base plates, guide rails, column caps, column bases, corbels, fences, stairs, curtain walls, flat steel and section steel, embedded reinforcement, embedded formwork, etc.

　　III. Features:

　　1. Wide construction temperature range, from 15°C to 40°C.

　　2. Non-expansion anchoring, no compressive stress on concrete, suitable for various base materials, and performs better on concrete with lower strength.

　　3. Safe and convenient (for example, the special inverted shape of the Hilti bolt resin capsule ensures that it does not fall during vertical surface hanging construction).

　　4. Small spacing and edge distance, suitable for narrow spaces.

　　5. Convenient installation and operation, rapid solidification after installation, and high load-bearing capacity.

　　6. Suitable for heavy loads and various vibration loads.

　　7. Large anchoring thickness.

　　IV. Process Principle:

　　By bonding the anchor rod and the hole wall with synthetic resin mortar, the anchor rod, the anchoring base, and the anchored object form a whole, thereby achieving the effect of fixing components or improving the load-bearing capacity of components.

　　V. Process Flow:

　　Installation procedure: Drilling - Hole cleaning - Insert resin capsule - Screw in bolt - Gel process - Hardening process - Fix object

　　1. Drilling: First, according to the design requirements, set the positions according to the spacing and edge distance on the drawings, and drill holes in the base. The hole diameter and depth must meet the design requirements.

　　2. Hole cleaning: Use tools such as an air pressure blowpipe to remove floating dust and dirt from the hole, keeping the hole clean.

　　3. Insert resin capsule: Insert the resin capsule into the clean hole. The capsule can only be used when the resin flows like honey at hand temperature upon insertion.

　　4. Screw in bolt: Use an electric drill to screw in the threaded rod until the resin flows out. Generally, an impact drill or hand drill is used at a speed of 750 rpm. At this time, the bolt is screwed in, the resin capsule is broken, and the resin, hardener, and quartz granules are mixed and fill the gap between the anchor and the hole wall. At the same time, the anchor can also be inserted into a wet hole, but the water must be drained from the hole, and the waiting time for the gel process and hardening process must be doubled.

　　5. Gel process: Keep the installation tool stationary. The chemical reaction time is shown in Table 1.

　　6. Hardening process: Remove the installation tool and wait for the resin to harden. The chemical reaction time is shown in Table 1.

　　7. Fix object: After the resin is completely hardened, add the washer and hex nut to fix the object.

　　VI. Quality Requirements and Control

　　1. When drilling, it is best to use a drill bit that matches the anchor, and the reinforcement must not be damaged.

　　2. Before construction, the mechanical properties of the anchor materials must be tested. Only after passing the test can they be used on site.

　　3. During on-site construction, tests to determine the on-site application conditions of the anchor should be conducted to fully verify the load-bearing capacity. The tests should be conducted not only in low-strength concrete but also in high-strength concrete. In the tests, the anchors are embedded according to the manufacturer's instructions for allowable load, corresponding spacing, edge distance, and component thickness. The tests use axial tensile force, shear force, and combined tensile-shear force to determine the influence of load direction on load-bearing capacity.

　　4. When cleaning the hole, the dust and floating ash in the hole must be cleaned thoroughly.

　　5. During winter construction, the resin capsule should be kept warm in advance to ensure that the capsule has sufficient fluidity when inserted into the drilled hole (the resin flows like honey at hand temperature).

　　6. The threaded rod must be screwed in with an electric drill, and must not be driven in directly.

　　7. There must be no standing water in the drilled hole.

　　VII. Construction Example and Application Effect:

　　In the seismic reinforcement project of the National Culture Palace, for the steel plate bonding of the edge beam of the 12th floor exterior wall of Section III, and the fixing of the catwalk in the exhibition hall of Section IV and the audience hall of Section I, a method combining YJ structural adhesive bonding and chemical anchor anchoring was adopted. The beam reinforcement in Section III is one-sided reinforcement, and chemical anchor anchoring was used to fully ensure the overall reinforcement effect and meet the requirements of design and seismic reinforcement.