It may be necessary to bolt to concrete when securing a heavy piece of machinery to a concrete floor, building A bridge, or when doing foundation repairs. There are many other uses specific to the type of bolt. The type of bolt you should use can be determined by the load it will bear as well as how and where it can be installed.
1. Cast-in-Place Anchor Bolts
A common type of concrete bolt is the cast-in-place anchor bolt. This is a threaded bolt that has been set in place and cast into a section of concrete, generally a building foundation or slab. The bolt threads at the end of the steel rod protrude from the concrete, and a washer and nut are used to hold the object being secured in place. Cast-in-place anchors come in different shapes: L-bolt, J-bolt, pigtail anchor with a 10-degree bend, or with a steel plate and hex nut. The anchor bolt has a stronghold because it is pre-cast, but it can be tricky to steady in wet concrete. It is usually used to tie walls to the foundation to make buildings more earthquake-proof.
2. Epoxy Bolts
An epoxy bolt is used in existing concrete. To install an epoxy bolt, a hole is drilled in the concrete, and the bolt is inserted along with an epoxy, which sets the bolt. Epoxy is actually stronger than the concrete it is set into. Epoxy bolts are ideal where there must be a close spacing of the anchors or they must be placed close to an edge where a typical anchor bolt would tend to blow out the concrete when hammered in.
3. Grout Bonded Concrete Anchors
These kinds of fasteners are anchored into existing concrete surfaces or structures. Instead of using epoxy, a high strength grout is used to secure the bolt. Grout has a few advantages over epoxy. It will not break down under high heat and it is easier to pump into the holes. It does take longer to set up, and it is not quite as strong a bond as the epoxy.
4. Wedge Bolts
A wedge bolt is also used in a hardened concrete floor. A hole is drilled in the concrete, and a wedge is inserted into the hole. Then, a bolt is inserted and screws into the wedge. The wedge tightens around the bolt, securing it.
5. Concrete Drop-In Anchors
A concrete drop-in anchor is a steel expansion sheath that is tapered at the bottom and has a cone-shaped expander plug. To install them, a hole is drilled, and the anchor is driven into the hole until it is flush with the concrete. Then, a special setting tool is used to expand the anchor. This anchor is used in light to heavy-duty applications.
Bolts must be spaced along the floor or wall to distribute the load that will be attached to them. Building codes typically dictate the spacing of those bolts. Anchor bolts are meant to be permanent once they are set in place so unless the concrete holding them is removed first they are not going anywhere. This can sometimes be problematic. For example, when moving heavy machinery in a factory, it can be difficult to move the machine without damaging the bolts.
In some instances, the old machine is making way for a new one with the same bolt pattern in the base, or another type of machine might be slated to be set there later on. In many instances, those anchor bolts are crucial to the precise setting of specific machinery whose placement is governed down to micro-millimeters. They cannot be damaged because they cannot be replaced at any small cost. That can mean taking out an entire pedestal in some cases and rebuilding it. You may never encounter this at home but then again you just might.
The availability and diversity of concrete bolts, fasteners, screws, and add-on concrete anchors on the market, however, makes doing so much simpler. Both the seasoned veteran Millwright and for the novice do-it-yourselfer alike to bolt anything to concrete with complete confidence in their work. Use only as directed.