Wedge Anchor Removal

Wedge anchors are designed to go into a predrilled hole in concrete and not come out.  To remove a wedge anchor from concrete, enough pullout force must be created that will meet the breaking point of the concrete in which the wedge anchor is installed.  The force needed depends on the depth of embedment in the concrete and the diameter of wedge anchor being installed.  This force, which is called the ultimate tension value, is shown in the table below. (Note that the column headings of 2000psi, 4000psi and 6000psi refer to the strength of the concrete.) 

An important consideration is that when the wedge anchor is pulled to the ultimate tension value, the concrete fails and both the wedge anchor and a cone of concrete is extracted.  There is only two ways to eliminate the wedge anchor from sticking above the concrete, which are:

  1. Using a cut off saw or grinding wheel, cut the wedge anchor off at the surface of the concrete.
  2. Before installing the wedge anchor, drill the hole two times the length of the wedge anchor being installed.  This will allow room for the wedge anchor to be pounded into the concrete and be flat with the surface of the concrete.  Remember, wedge anchors are designed to go into a hole in the concrete and not come out, so it is possible for the wedge anchor, after it is set, to be pounded into the concrete.

Concrete Wedge Anchor – Embedment Depth and Tension

Wedge Anchor Diameter (in)

Embedment Depth (in)

Torque ft/lbs

2000 psi (Tension)

3000 psi (Tension)

1/4

1-1/8

 

1170

1771

1/4

1-3/4

5-10

1841

2408

1/4

2-3/4

 

1975

2748

3/8

1-1/2

 

1631

3636

3/8

3

25-30

3229

5653

3/8

5

 

4075

6328

1/2

2-1/4

 

3999

6714

1/2

4

50-60

6336

8942

1/2

6

 

6902

10175

5/8

3-3/4

 

4999

8747

5/8

5

75-90

8854

15590

5/8

7

 

9381

16710

3/4

3-1/4

 

6638

11314

3/4

6

150-175

10084

18408

3/4

8

 

11170

19805

7/8

3-7/8

 

8392

16354

7/8

5-3/4

200-250

12064

18250

7/8

8-3/4

 

12784

16850

1

4-1/2

 

9773

18250

1

7-1/2

250-300

11800

26726

1

10

 

15590

30491

1-1/4

5-1/2

 

17550

22971

1-1/4

7

400-450

21050

27845

1-1/4

10

 

27893

24788



Holding Values

The wedge anchor is an expansion anchor that creates an outward force against the sides of the hole in the concrete.  This outward force transfers the energy to the concrete to create the holding values via friction of the wedge anchor in the concrete.  The expansion force is in the shape of a “V” when pictured from a side view. If the wedge anchor is pulled to concrete failure then the concrete pullout will be in the shape of a “V” or cone shaped.

Embedment Depth

The depth of embedment of the wedge anchor into the concrete is one factor that determines the holding values that the wedge anchor will obtain.  The deeper that the wedge anchor is embedded into the concrete, then the better the holding values will be.

Minimum Embedment Depth

Each diameter of wedge anchor requires that it is embedded into the concrete a minimum distance in order for the wedge anchor to attain its minimum holding strength.  The larger the diameter, then the deeper the minimum embedment into the concrete must be when the wedge anchor is installed.

Torque Values

Each diameter of wedge anchor has a range of torque values that the wedge anchor must be to reach minimum holding values.  A torque wrench can be used during the installation process, or it can be used to check the torque value of any wedge anchor once it is installed.

Different Types

Wedge anchors are manufactured from different types of steel, such as standard carbon steel, 303 stainless steel, 304 stainless steel and 316 stainless steel.  The holding values and the removal of the wedge anchor are not dependent on the type of steel from which the wedge anchor is manufactured.

Different Manufacturers

Although all wedge anchors work on the same principles, each manufacturer has its own brand names for their wedge anchors.  Regardless of whose wedge anchor is being used, the two methods for removal remain the same.  The holding values, as stated in the chart above, may vary from one manufacturer to another.  The chart refers to the wedge anchor manufactured by Concrete Fastening Systems, Inc.





 

Please remember with all fastening jobs to keep safety in mind. Always follow safety instructions on all tools, and refer to manufacturer's installation instructions when available and always remember to wear safety goggles!

Article written by: Bob Carlisle, President Concrete Fastening Systems, Inc

Back to Section