Rebar Knowledge Center Installing Post-Installed Rebar

INSTALLING POST-INSTALLED REBAR
Things to consider for reinforcing bar installation
Working with post-installed reinforcing bars can involve many caveats that can limit the effectiveness of
the original design. Some, but by no means all, of the installation aspects relative to post-installed
reinforcing bars are discussed in the following pages. Your primary source of information for post-installed
reinforcing bar installation should be the Manufacturer’s Printed Installation Instructions (MPII) for the
specific adhesive system you are using to install your reinforcing bars. Always follow the MPII with
respect to post-installed anchor and reinforcing bar installation.

Step 1: Locate existing reinforcement
Locating existing reinforcement is generally accomplished by one of the following scanning methods:
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Scanners that locate ferrous materials using magnetic fields
Scanners that utilize ground-penetrating radar technology, or GPR
X-ray scanning equipment

In general, ferrous scanners such as the one shown in
the figure to the right provide the bar location and size
for rebar located within 8-10 inches of the concrete
surface. GPR scanners are capable of locating
ferrous and non-ferrous embedded items, such as
aluminum conduit. X-ray scanning is typically used for
heavy congestion areas or where existing reinforcing
bars are too deep for ferrous or GPR system
detection. It is generally preferable to supplement
rebar scanning results with original design documents
or as-built plans if available.

Step 2: Roughen the existing concrete surface
Roughening the existing concrete surface is typically specified when new concrete will be applied to
existing concrete. Roughening the existing concrete surface prior to casting new concrete not only
provides for increased adhesion, but also increases the joint’s ability to transfer shear through shear
friction. In cases where the surface layer of existing concrete is carbonated, the carbonated layer should
be removed in areas that will receive post-installed reinforcing bars. ACI 318-11, Section 11.6.9 requires
roughening "...to a full amplitude of approximately 1/4 in." This may be accomplished by mechanical
means, sand-blasting or water-blasting. Any loose material should be removed from the roughened
surface prior to placing new concrete.

Step 3: Choose a drilling method
Post-installed reinforcing bars designed for development can require deeper embedments than postinstalled reinforcing bars designed using anchoring-to-concrete provisions. To achieve these deeper
embedments, one of the following three drilling methods is typically employed:
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Rotary-impact drills, or hammer drills, equipped with standard or cruciform carbide bits
Percussive rock drills
Diamond core drills utilizing either wet or dry coring technology

Each method has its own advantages and disadvantages. Hammer drills are the preferred tool for most
applications given their portability and ease of use. They produce a non-uniform hole surface especially
suited for enhancing the adhesive bond, provided correct hole cleaning procedures are used. For deeper