Fastening products to concrete and brick is a challenge for builders, industries, and homeowners alike. While fastening to wood and plastic is easy, fragile materials are problematic and require special devices. This is where concrete anchors come in. Usually they are made mortgages when pouring the foundation, basement, walls. But in the future, it may be necessary to re-profiling or repairing the premises. More elements are needed here.
What is an anchor
Anchor is a part intended for fastening products and structures to solid foundations made of building materials, primarily concrete, stone and brick. A hole is drilled under it, in which the fastener is held by friction, gluing or stop. Anchor is installed in concrete by wedging metal galvanized fasteners of a special design.
What determines the reliability of the connection
The following factors affect the quality of the connection:
- characteristic of the base (concrete, brick, stone);
- correspondence of the size and type of fasteners to the applied loads;
- preparation and installation technology;
- fastener strength.
The anchor is driven into a hole drilled in a concrete or brick structure: foundation, wall, partition, floor slab. With its help, beams, channels, suspended ceilings, chandeliers, railings, load-bearing structures of great weight are fixed. In this case, the base must be strong enough.
How concrete anchors are attached
Anchors are attached by wedging the sleeve inside a drilled hole or with glue.
Types of mechanical anchors
The simplest fastening is a driven anchor with an internal thread. It is inserted into a pre-prepared hole, unclenched with a special device and the fasteners are screwed in.
A common type is an expansion anchor for concrete, equipped with a wedge.
It is designed for high loads and can even be used to install machine tools or heavy garage doors. The principle of operation consists in wedging the shell mounted on the stud with a conical shank and creating an obstacle to reverse movement. At the same time, the base of the building material must have the necessary mechanical properties to withstand the expansion and weight loads.
To tighten the wedge anchor after it is installed, you need a special center punch, which is inserted inside and wedge the sleeve with a hammer. Then the toolremove and tighten the fixing screw.
In another wedge anchor design, tightening is done with a nut that rests against the surface of the base, moving a threaded stud with a cone at the end. The cone enters the sleeve, which expands and fastens. If the sleeve is made with teeth, then it cuts the concrete, forming a cone inside. The fastening is stronger, because in addition to the bursting force, an additional emphasis appears in the axial direction.
Another device contains a cone system that tightens the spacer on both sides. Due to this, the friction surface increases by 2 times. These anchors are used to fasten structures of medium and heavy weight to concrete and natural stone.
The rod anchor is similar to the wedge anchor, only it is longer. It is used to connect multilayer systems, for example, insulating and facing materials. The inner rod can be cut to the required length. The end with a wedge is inserted into a hole drilled in concrete, and on the other hand, the rod is tightened with a nut and washer. The rod anchor is often used for building facades.
The frame anchor contains 2 wedging zones, one of which is located in the base, and the other in the attached part. When tightening the bolt, it is firmly fastened with a double tightening.
Depending on the purpose, the type of anchor for concrete is selected. Dimensions, types and characteristics are given in the tables, which determine their compliance with the calculatedloads.
Chemical anchors
Concrete anchors can be installed with an adhesive such as polymer resin. To do this, they fill a well-cleaned hole by 2/3. After that, the anchor is inserted with a translational-rotational movement. Instead, you can use a regular hairpin or other fasteners. After the glue has hardened, the structure or part can be attached to the anchor. When properly installed, it is able to withstand significant loads. A chemical anchor is indispensable when installing in porous materials, such as foam concrete or aerated concrete. Mechanical fastening is not suitable here due to the low strength of the base.
Increasing the reliability of the connection is created through the use of inorganic (cement) and organic (highly reactive resin) components as glue. The cement provides good compatibility with the substrate and high mechanical properties.
Reinforcing bars, bolts, threaded studs, bushings with internal thread are fixed with chemical anchoring. Special injection systems for supplying glue have been developed. It is pumped into the connector quickly and in portions, which minimizes consumption. In this case, cylinders with different capacities and solutions with different polymerization rates are used. Press guns can be pneumatic or battery operated.
For chemical anchoring, it is important that the holes in the base are clean. For this, special blowing devices with sets of brushes are used in the equipment kit.
In the case of porousbuilding materials, it is preferable to choose chemical anchors for concrete. Prices here largely depend on the type and quantity of glue, as well as the injection system, with which even simple embedded elements can be fastened: studs, bolts, reinforcement, etc.
Conclusion
The correct choice of the type of anchor for concrete and the technology of its installation will create a reliable and durable connection. For all types, there are tables with characteristics that can be used to find the optimal solution.
