Post-Installed Reinforcing Bar Guide
3.0 HOW ARE THEY INSTALLED ?
Jobsite constraints should be taken into consideration while designing and installing post-installed reinforcing bars .
Note : In addition to state-of-the-art adhesive anchoring systems , Hilti offers best-in-class detection and drilling equipment to facilitate the installation of post-installed reinforcing bars over a wide range of bar diameters and embedments .
3.1 LOCATION OF EXISTING REINFORCEMENT AND OTHER EMBEDDED ITEMS
The location of existing reinforcement is generally accomplished with one or more scanning methods . These may be generally categorized as :
a . Scanners that locate ferrous materials using magnetic fields ( ferrous scanners , see Figure 21 ),
b . Scanners that utilize GPR ( ground-penetrating radar technology ), and
3.2 ROUGHENING THE EXISTING CONCRETE SURFACE
Surface roughening prior to casting new concrete against existing provides not only for increased adhesion , but also increases the ability of the joint to transfer shear through shear friction . Where new concrete is to be applied to an existing concrete surface , roughening of the existing concrete surface is typically specified10 . In cases where the surface layer of existing concrete is carbonated , the carbonated layer should be removed in areas that are to receive post-installed reinforcing bars . A rule of thumb is to remove the carbonated concrete over a circular area given by the diameter of the bar plus 2-1 / 2 inches .
ACI 318-19 Table 18.104.22.168 requires roughening "... to a full amplitude of approximately 1 / 4 in ." This may be accomplished by mechanical means ( e . g ., using a Hilti TE 76 ATC equipped with a bushing tool , see Figure 22 ), sandblasting or water-blasting . It should be ascertained that the resulting surface does not contain loose material prior to placing new concrete . c . X-ray scanning equipment .
For reinforcing bars located within 8-10 inches of the concrete surface , ferrous scanners provide both bar location and size . For location of both ferrous and non-ferrous embedded items ( e . g ., aluminum conduit ), GPR-based scanners are appropriate . For areas of heavy congestion or where existing reinforcing is too deep for ferrous or GPR systems , x-ray scanning methods may be necessary . Where available , it is generally preferable to supplement scanning results with as built or original design documents .
Figure 22 — Roughening a concrete surface with a Hilti TE 70-ATC Combihammer .
Figure 21 — Using a Hilti PS 300 hand-held Ferroscan scanner to locate and map existing reinforcing prior to beginning drilling .
10 ) See ICRI Technical Guideline No . 310.2 Selecting and Specifying Concrete Surface Preparation for Sealers , Coatings and Polymer Overlays or ASTM E965 Standard Test Method for Measuring Pavement Macrotexture Depth Using a Volumetric Technique .