Question:

What is your experience with anchor bolts and anchor bolt installation?

Answer:

Anchor bolts hold or "anchor" equipment or machines or structures to structures. Anchor bolts require a template or a "plan" to make them fit the equipment sole plates or the holes of the column base plate. Promote the use of the template mentioned or some precise layout of the anchor bolt positions.

Consult the plans and they will provide information concerning position and diameter of the anchor bolts. Double check your installation details because in this case we are "casting in concrete."

When design precedes construction, the larger diameter bolts are usually cast into the fresh concrete. Expect to work with ironworkers, millwrights, and machinery manufactures in such cases. Again, promote the use of a template to hold the bolts in place during the placement of concrete.

Expect to be able to place anchor bolts after the concrete is cast. It is a situation that is more common than one would expect. Drilling of the concrete is required to create a void for the anchor bolt. Hole depth and diameter need to be specified to the installation crew.

"Guessing" is concerning bolt diameter and bolt length is a poor practice.

Post placed anchor bolts are inserted in the drilled hole and grouted tightly into place. A template is a good idea for positioning the drill holes and again a good idea to align the bolts hanging in those same holes.

There are differing schools of thought concerning grouting the anchor bolts. One school of thought requires the bolts be hung in the holes and the template be chaired up and fixed tightly into place. Once this work is accomplished, the grout is mixed and placed in and around the bolts.

The other school of thought is to have the bolts and template at the ready. Pre-grouting the holes first. Filling the clean and prepared hole to full or near full with the fresh grout. Then the bolts would be forcefully driven into place and aligned by fitting them to the template before e the grout hardens. Once the bolts are driven home and aligned in the template, they are protected and allowed to set undisturbed until the grout sets hard.

One option not discussed is to "sleeve" the intended location of the anchor bolt and avoid the need to drill the hole into the hardened concrete. The concrete can harden and the anchor bolt placement and grouting can take place later in the schedule.

The easiest and most performance-oriented product to grout in anchor bolts is L&M Crystex Grout. Crystex is cementitious, non-shrink and very fluid. Normally, fluidity is an indicator of lower strength. Not in the case of Crystex. Fluidity is formulated into the grout mixture and when only the addition of a minimum amount of water, Crystex becomes fluid and easy to place or pour.

EpoGrout 758 is the anchor bolt professionals choice of an epoxy grout to fill the void surrounding an anchor bolt. Long work time, low exothermic heat and high bond strengths make EpoGrout 758 unique in its performance surrounding anchor bolts or under dynamic machinery.

Crystex Grout or EpoGrout 758 will provide the installer with a professional and profitable installation.

Byron D. Hanson CET
L&M Construction Chemicals