How to Remove a Broken Anchor Bolt from Concrete
Assess the Damage
Begin by determining the extent of the damage. If the bolt head is still intact but the shaft has snapped off below the surface, you may be able to remove it with a bolt extractor. However, if the bolt head has been sheared off or the shaft has broken deep within the concrete, more drastic measures may be necessary.
Use a Bolt Extractor
For a broken bolt with an intact head, a bolt extractor can be effective. Drill a pilot hole into the center of the bolt head and insert the extractor. Use a wrench or pliers to turn the extractor counterclockwise to gradually loosen and remove the bolt.
Cut and Pry the Bolt Out
If the bolt head is sheared off, use a rotary tool or hacksaw to cut a groove into the remaining shaft just below the concrete surface. Insert a flathead screwdriver or pry bar into the groove and gently pry the bolt out.
Drill and Extract the Stub
For bolts that have broken deep within the concrete, drilling is the most reliable method. Drill a hole slightly larger than the bolt diameter and slightly deeper than the bolt length. Insert a threaded extractor into the hole and turn it counterclockwise to embed its teeth into the bolt stub. Use a wrench or socket to unscrew the extractor and remove the stub.
Chemical Adhesive Removal
If the bolt is bonded to the concrete with a chemical adhesive, apply a solvent designed to dissolve the adhesive. Allow the solvent to penetrate for the recommended time and then attempt to remove the bolt using the techniques described above.
Heat and Expansion
For bolts that have expanded due to corrosion or other factors, heat can be applied to expand the bolt and break the bond with the concrete. Use a heat gun or blowtorch to heat the bolt for several minutes, then quickly try to pry it out.
Chiseling and Breaking
In extreme cases, it may be necessary to chisel away the surrounding concrete to expose the broken bolt. Use a chisel and hammer to carefully remove the concrete without damaging the surrounding structure. Once the bolt is exposed, you can attempt to break it into smaller pieces using a chisel or hammer.
Rotary Hammer and Drill Bit
If the bolt is embedded deep in the concrete, a rotary hammer and drill bit can be used to break the bolt into smaller pieces. Drill several holes around the perimeter of the bolt and gradually increase the size of the holes until the bolt is weakened and can be removed.
Professional Help
If you are unable to remove the broken anchor bolt on your own, it is advisable to seek professional help. A contractor with specialized equipment and expertise can assess the situation and determine the most effective removal method.
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