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The following are practical steps for removing concrete anchors:
Content
I. Identify the Anchor Type Before Starting
▸ Expansion Bolts (most common):
Features: Has a tapered sleeve at the end; expands and grips the hole wall when tightened.
Removal Method: Loosen the screw first → tap the bolt with a hammer → pull it out with pliers.
▸ Chemical Anchors (grouted):
Features: Adhesive is injected into the hole, bonding the bolt in place.
Removal Method: Use a rotary hammer to break the surrounding concrete → cut the bolt at the base.
▸ Embedded Anchors (embedded during casting):
Features: Has a threaded sleeve or steel plate.
Removal Method: Cut with a gas torch (do not pull forcefully, as this will damage the concrete).
II. General Removal Steps
▸ Scenario 1: Expansion Bolts/Ordinary Anchors
Remove the load:
Remove any heavy objects such as pipes or brackets attached to the anchor.
Loosen the screw/nut:
Use a wrench to loosen counterclockwise (use WD-40 rust remover if rusted).
Tap to loosen:
Tap the bolt head from the side with a hammer (to break the bond between the expansion sleeve and the concrete).
Pull out with pliers:
Grip the bolt head tightly with pliers, and pull while rocking it (avoid brute force to prevent breakage).
▸ Scenario 2: Chemical Anchors/Stubborn Anchors
Drill holes to weaken:
Use a power drill to drill angled holes next to the anchor (to weaken the adhesive bond).
Local crushing:
Use a rotary hammer and chisel to break the concrete around the anchor (exposing 5cm of the anchor rod).
Cutting:
Use an angle grinder to cut the anchor flush (fill the remaining hole with mortar).
III. Professional Tool List
| Tool | Purpose | Alternative Method |
|---|---|---|
| Rotary Hammer + Chisel Bit | Breaks concrete around anchor | Sledgehammer + Pry Bar (slower, labor-intensive) |
| Angle Grinder | Cuts exposed bolt head or shank | Hydraulic Shear (for heavy anchors) |
| Locking Pliers / Pipe Wrench | Grips and twists anchor for extraction | Cheater Pipe over Wrench (leverage boost) |
| Penetrating Oil (e.g., WD-40) | Loosens rusted threads | Diesel Soak (less effective) |
IV. Avoiding Pitfalls
▸ Consequences of forceful removal:
The anchor bolt breaks inside the hole (making removal more difficult) or the concrete cracks (requiring repair).
▸ Safety Red Flags:
When removing anchor bolts at height, ensure no one is below!
Wear safety glasses when drilling holes for chemical anchors (to prevent flying debris).
▸ Leaving a way out:
Before removing anchor bolts in critical structures, an engineer must confirm that it will not affect load-bearing capacity.
V. How to repair after removal?
▸ Small holes (<20mm):
Fill directly with high-strength mortar and smooth the surface.
▸ Large holes (exposing rebar):
Chisel into a square hole → apply bonding agent → pour expanding concrete.
