Fixing products to concrete and brick is a problem for builders, industrial enterprises, as well as homeowners. If fastening to wood and plastic is not difficult, then fragile materials have problems and require special devices. Here, concrete anchors come to the rescue. Usually they are mortgaged when pouring the foundation, basement, walls. But in the future there may be a need for reprofiling or repairing the premises. Other elements are needed here.
What is an anchor
An anchor is a part intended for fastening products and structures to solid bases made of building materials, primarily concrete, stone and brick. A hole is drilled under it , in which the fastener is held due to friction, bonding or abutment. Installation of the anchor in concrete is carried out by the method of wedging galvanized metal fasteners of a special design.
What determines the reliability of the connection
The following factors affect the quality of a connection:
- foundation characteristics (concrete, brick, stone);
- compliance of the size and type of fasteners to the applied loads;
- preparation and installation technology;
- fastener strength.
An 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, heavy-weight supporting structures are fixed. In this case, the base must be strong enough.
How to anchor concrete
Anchors are fastened by wedging the sleeve inside the drilled hole or on glue.
Types of mechanical anchors
The simplest fastening is a driven anchor with internal thread. It is inserted into a pre-prepared hole, unclenched with a special device and screw fasteners.
A common view is an expansion anchor for concrete, equipped with a wedge.
It is designed for high loads and with its help you can even install machines or heavy garage doors. The principle of operation is to wedge a cone mounted on a stud with a conical shank and create an obstacle to the reverse movement. At the same time, the base of the building material must possess the necessary mechanical properties to withstand the spacer and weight loads.
To tighten the wedge anchor after installing it, you need a special beard punch, which is inserted inside and wedged the sleeve with a hammer. Then the tool is removed and the fixing screw is screwed.
In another design of the wedge anchor, tightening is performed using a nut that abuts against the surface of the base, moving the stud with a thread and a cone at the end. The cone enters the sleeve, which expands and consolidates. If the sleeve is made with teeth, then it cuts the concrete, forming a cone inside. The fastening is stronger, since in addition to the bursting force, an additional stop appears in the axial direction.
Another device comprises a cone system that tightens the spacer sleeve on both sides. Due to this, the friction surface increases 2 times. These anchors fasten medium and heavy structures to concrete and natural stone.
The core anchor is designed by analogy with the wedge, only has a large length. With its help, multilayer systems, for example, insulating and facing materials, are connected. The inner core can be cut to the required length. The end with the wedge is inserted into the hole drilled in concrete, and on the other hand the rod is tightened with a nut and washer. The rod anchor is often used to decorate 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 calculated loads.
Chemical anchors
Concrete anchors can be installed on glue, such as polymer resin. To do this, they fill a well-cleaned hole in 2/3. After insert the anchor translational-rotational motion. Instead, you can use a regular hairpin or other hardware. After the adhesive has set on the anchor, a structure or part can be attached. With proper installation, it is able to withstand significant loads. The chemical anchor is indispensable when installed in porous materials, such as foam concrete or aerated concrete. Mechanical fastening is not suitable here due to the low strength of the base.
Improving the reliability of the connection is created due to the use of inorganic (cement) and organic (highly reactive resin) components as glue. Cement provides good base compatibility and high mechanical properties.
Reinforcing rods, bolts, threaded rods , bushings with internal thread are fixed by chemical anchoring. Special injection glue supply systems 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 purpose, special blowing devices with brush sets are used in the equipment set.
In the case of the use of porous building materials, it is preferable to choose chemical anchors for concrete. Prices here are more dependent on the type and quantity of glue, as well as the injection system, with which you can even fix simple embedded elements: studs, bolts, fittings, etc.
Conclusion
The right choice of type of concrete anchor and its installation technology will create a reliable and durable connection. For all types, there are tables with characteristics by which you can find the optimal solution.