Chemical bolts rely on the combined effect of the grip force and mechanical interlocking force between the bolt and the concrete to resist uplift and the bolt itself to resist shear. They are mainly used at the connection points of new and old structures.
You can find the mechanical indicators from the product introduction provided by the manufacturer. When calculating, you should refer to the data provided by the manufacturer because the chemical adhesives produced by different manufacturers vary, and so does their bonding capacity. Chemical bolts are a type of post-installed anchor and are used when embedded parts are missed or in post-construction projects.
Chemical Bolts
The chemical bolt anchoring technology belongs to the category of post-reinforcement techniques. In recent years, as a new, simple and effective post-fixing method, the application of chemical bolt anchoring construction has been widely adopted in building renovation, changes in building usage, or the expansion and renovation of existing buildings.
I. Introduction to Chemical Bolts
1. Composition of Chemical Bolts: Chemical bolts consist of chemical tubes, screws, washers and nuts. The screws, washers and nuts (hexagonal) are generally made of galvanized steel and stainless steel (can also be hot-dip galvanized as required). The chemical tubes (or plastic-wrapped agent tubes) contain reactive resins, curing agents and quartz particles.
2. Relevant Parameters of Chemical Bolts
Drilling depth: The required drilling depth is determined by the type and size of the anchor bolt. Except for a few exceptional cases, it is generally greater than the anchoring depth. During drilling, the control of the drilling depth is particularly important.
If the corresponding manufacturer’s anchor bolt is used, there will be a matching automatic depth control drill (for example, the German Feuerhand brand anchor bolt has a matching high-tech column cone universal drill bit FZU for drilling, making the drilling process very convenient).
Anchoring depth: The distance from the surface of the anchoring structure to the bottom of the screw, which is an important parameter affecting its bearing capacity.
Anchoring thickness: The anchoring thickness is equal to the thickness of the object to be anchored. If the anchoring base is at least covered with plaster or tiles, insulation layer, etc., the anchoring thickness should be at least equal to the thickness of the plaster or tiles, insulation layer, etc., plus the thickness of the object to be anchored.
Edge distance: It refers to the distance from the axis of the anchor bolt to the free edge of the component. Spacing: It refers to the distance between the axes of adjacent anchor bolts. Component thickness: It refers to the thickness of the anchoring base.
To ensure the maximum bearing capacity of an anchor bolt, a certain spacing, edge distance and component thickness must be guaranteed. The data is generally based on the technical parameters provided by the manufacturer.
II. Scope of Application
1. It is applicable to ordinary concrete with a strength grade of C15 or above (un-cracked concrete) and dense natural stone.
2. It is used for fixing ordinary steel structures, bases, guide rails, column caps, column feet, corbels, fences, stairs, curtain walls, flat steel and shaped steel, embedded reinforcing bars, embedded formwork, etc.
III. Features
1. The construction temperature range is wide, from 15°C to 40°C.
2. It is an anchor without expansion force, which does not exert compressive stress on concrete. It is suitable for various substrates and performs better on concrete with lower strength.
3. It is safe and convenient (for example, the special upside-down shape of the Hilti bolt cartridge ensures that it will not fall during vertical surface hanging construction).
4. The spacing and edge distance are small, making it suitable for narrow spaces.
5. It is easy to install and operate, and can quickly solidify after installation, with high load-bearing capacity.
6. It is suitable for heavy loads and various vibration loads.
7. It has a large anchoring thickness.
IV. Process Principle
By bonding the anchor bolts and the hole walls with synthetic resin mortar, the anchor bolts, the anchoring base and the object to be anchored are formed into a whole, thereby achieving the effect of fixing components or enhancing the load-bearing capacity of components.
V. Process Flow
Installation Procedure: Drilling – Hole Cleaning – Inserting the Agent Tube – Inserting the Bolt – Gelation Process – Hardening Process – Fixing the Object
1. Drilling: First, according to the design requirements, determine the position based on the spacing and edge distance on the drawing, and drill holes on the base layer. The hole diameter and depth must meet the design requirements.
2. Hole Cleaning: Use tools such as air pressure blow tubes to remove the floating dust and dirt in the hole to keep it clean.
3. Inserting the Agent Tube: Insert the agent tube into the clean hole. Only when the resin can flow like honey at hand temperature can the rubber tube be used.
4. Inserting the Bolt: Use an electric drill to screw in the bolt until the agent flows out. Generally, an impact drill or hand drill is used, with a drilling speed of 750 revolutions per minute. At this time, as the bolt is screwed in, the agent tube will break, and the resin, curing agent and quartz particles will mix and fill the gap between the anchor bolt and the hole wall.
Meanwhile, the anchor bolt can also be inserted into a wet hole, but the water must be drained from the hole, and the waiting time for the gelation process and hardening process must be doubled.
5. Gelation Process: Keep the installation tool in place.
6. Hardening Process: Remove the installation tool and wait for the agent to harden.
7. Fixing the Object: After the agent is completely hardened, add a washer and a hexagonal 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 bolt and must not damage the reinforcing bars.
2. Before construction, material mechanical property tests must be conducted on the anchor bolts. Only after passing the tests can they be used on site.
3. On-site application condition determination tests for the anchor bolts should be carried out during on-site construction to fully verify the bearing capacity. The tests should be conducted not only in low-strength concrete but also in high-strength concrete.
During the tests, the allowable load, corresponding spacing, edge distance, and component thickness should be determined according to the manufacturer’s instructions for embedding the anchor bolts. The tests should be conducted under axial tension, shear force, and combined tension-shear force to determine the influence of the load direction on the bearing capacity.
4. During hole cleaning, all dust and loose particles inside the hole must be thoroughly removed.
5. In winter construction, the chemical tubes should be pre-insulated to ensure sufficient fluidity when inserted into the drilled holes.
6. The screws must be screwed in with an electric drill and must not be directly hammered in.
7. There must be no water accumulation in the drilled holes.
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