Anchor fasteners are used to connect structural elements of base material to masonry and concrete in buildings and structures. They are installed by first drilling a hole in the base material. The hole is slightly larger than the fastener. Then the anchor is inserted into the hole in the right manner. The distance to which the anchor penetrates the base material is called the embedment depth. There are two types of anchor fasteners namely, mechanical anchor fasteners and chemical anchor fasteners, each of them is discussed below.
Mechanical anchor fastener
Mechanical anchor fasteners use friction to anchor themselves in place. It is used to expand in diameter when it is pushed into the hole. This expansion grips the base material tightly and causes the anchor to be firmly wedged in place. Today, a variety of anchors are available to meet different applications. Mechanical anchors generally fall into two categories, Cast-in-place and Drilled-in anchor fasteners, each of the anchor types is given below.
Mechanical expansion anchors – can be loaded immediately after installation. Steel expansion anchors generally have better resistance to heat or fire. They can be further divided into two categories torque-controlled which is inserted into the hole and secured by applying a specified torque to the bolt head or nut with a torque wrench and displacement controlled which consist of an expansion sleeve and a conical expansion plug, whereby the sleeve is internally threaded to accept a threaded element.
Clamping anchors – used to anchor two or four core insulated bundled cables, all of which have equal cross-sectional areas. The clamp is tightened by bolting and is designed to avoid damage to the cable insulation. The product can be used along with various types of hook bolts.
Concrete wedge anchors – work by inserting them into a hole drilled into concrete. The concrete wedge anchor is then expanded, wedging itself securely in the concrete. These are available in zinc plated carbon steel for indoor dry applications, hot-dipped galvanized for most outdoor applications. This anchor helps prevent rust in dry environments; dependable application and maintenance.
Anchor rods – embedded in concrete foundations to support light poles, traffic signal poles, structural steel columns, highway sign structures. Anchor rods can be cast-in-place or post-installed in an existing concrete slab. These are readily available as stock items or manufactured to meet a variety of ASTM grades and configurations depending on the application.
Screw anchors – made from plastic, metal, or fiber, which enable the attachment of screws into brittle materials. Screw anchors are placed into difficult materials to prepare for the insertion of screws.
Under anchors – the force-transfer mechanism of this type of anchor is based on the mechanical interlock. A special drilling operation allows creating a contact surface between the anchor head and the hole’s wall where bearing stresses are exchanged.
Sleeve anchors – can be used in a variety of base materials, and they are available in a wide variety of diameters, lengths, and head styles. They come preassembled, so they are ready for immediate installation. There are four different head styles, although not all diameters are available in each head style. The head styles are acorn, hex, round, or flat countersunk heads.
Nail anchors – used for lightweight anchoring into solid masonry and hollow wall applications. The nail in anchor is simple to use and ideal for a variety of applications. It is available with a standard zinc pin or a stainless pin for use in marine applications. It is also available in a wholly metal pin anchor for heavier anchoring applications. Please see attached table on each item for grip range, drill size and hole depth.
Plastic anchors – used for mounting in porous materials such as concrete, lightweight concrete and brick. Its force-transfer mechanism is similar to mechanical expansion anchors. A torque moment is applied to a screw that is inserted in a plastic sleeve. As the torque is applied the plastic expands the sleeve against the sides of the hole acting as expansion force.
Drywall anchors – fitted for the location you want something hung and there’s not a stud behind it. A drywall anchor goes between the screw and the drywall, biting into the drywall much more effectively than a screw would. Then, you screw in to the anchor, so everything stays in place.
Tapcon anchors – stands for self-tapping (self-threading) concrete screw. This type of fastener requires a pre-drilled hole using a Tapcon drill bit and is then screwed into the hole using a standard hex or phillips bit.
Insulation anchors – plastic or metal fixings with a large circular head. The insulation anchors have slightly different uses depending on their design, so different anchors are used for different types of insulation and substrate. These anchors are used for attaching insulation to a surface that comes in different varieties of Plated Steel, Galvanized Steel and Stainless Steel. When installing insulation, it is important to have the correct fixings to ensure your insulation remains secure, efficient and in place.
Chemical anchor fastener
Chemical anchors are used for fastening to concrete and similar substrates that provide more flexibility than mechanical anchoring. In this type of anchor, a resin is injected into the hole before insertion of the stud. With this, the chemical naturally fills in all irregularities and therefore makes the hole airtight and waterproof. The main importance of chemical anchors and fillings is that they form very strong bonds. These bonds are stronger compared to the base materials. There are different types of chemical anchors used in structures with different specifications as discussed below.
Polyester chemical anchors – a reactive resin used for the production of 2-component injection mortar. They are used for fixing steel dowels, staircases, handrails, building facades, sound barriers, pipelines, awnings, brackets, post-installation rebar connections.
Unsaturated polyester chemical anchors – used for the production of a 2-component injection mortar, whereby both unsaturated polyester resins dissolved in styrene and styrene-free unsaturated polyester resins with styrene related monomers as a reactive solvent are used.
Vinylester chemical anchors – fast curing anchoring resin for quick setting on vertical or overhead installation. It’s also efficient for cold weather with workable hardening time. has an excellent performance in resistance to acid and alkali. It is a good choice for chemical industry installation projects.
Epoxy acrylate chemical anchors – a two-component resin of styrene-free epoxy acrylate for use in concrete and masonry. It is designed as a fast curing, high-strength resin fixing anchor for very high 0loads and critical fixings especially in corrosive environments or damp conditions.
Pure epoxy standard anchors – a bonded anchoring system for use in cracked and uncracked concrete under normal and seismic conditions. Developed for the most demanding structural applications and rebar connections, it has a very high load-bearing capacity. Its applications include anchoring of threaded rods, reinforcing bars or internally threaded rod sleeves into concrete (normal, porous & light) as well as solid masonry.
Hybrid chemical anchors – a system includes a two-part chemical anchor that is designed to cure fast so you can load the fastening point earlier than you could with an epoxy anchor. It can be used anywhere requiring a threaded rod or rebar into concrete. Whether you require anchorage for structural steel connections such as steel beams or columns to concrete, structures such as racking, sound barriers or fencing, Highly reactive resins can be injected into the borehole before the insertion of the steel stud or bolt.
Resin anchors – used for anchoring reinforcing bars, dowels & holding down bolts. These are resistant to vibration as well as corrosion resistant. It has a fast setting property and compressive strength.
Chemical threaded anchor rods – pre-sized metal anchors especially for use with chemical masses and resin ampoules.
Powder – actuated anchors – used for steel-to-steel connection. A screw is inserted into the base material via a gas-actuated gas gun. The driving energy is usually provided by firing a combustible propellant in powder form. The fastener’s insertion provokes the plastic deformation of the base material which accommodates the fastener’s head where the force transfer takes place.
Discussed above are different types of anchor fasteners used for different applications. Each one of them comes with its own swpt of advantages and specifications. In an upcoming series of article we will discuss in brief all each type of mechanical and chemical anchor fasteners.