Product Technical Guides : US-EN Post-Installed Rebar Guide - Page 17

Post-Installed Reinforcing Bar Guide
with the ANSI B212.15 standard for carbide drill bit dimensions . The Hilti SafeSet system performs equally well in dry and wet concrete .
Figure 27 — Drilling with a Hilti rotary percussive drill equipped with Hilti SafeSet™ technology .
Figure 25 — Inclined core drilling with a Hilti drill stand .
Rock drills offer speed and efficiency and produce a rough hole surface that is suitable for bond , but the larger impact energy associated with rock drills may increase the tendency for damage in the concrete member , particularly if used in applications with small edge distance or reduced backside cover . Rock drills typically require larger edge distances / member thickness ( see Section 3.3 ). For applications involving rock drilled holes , contact Hilti . For longer embedment depths , core drills are generally the preferred option ( Figure 26 and Figure 27 ).
In contrast to hammer drills , which fracture the concrete with impact energy , core drill bits utilize a sacrificial matrix containing diamond fragments to abrade the concrete . Hilti diamond core bits with laser-welded segments offer long life and exceptional drilling efficiency . Using extensions , core drills can produce very long , straight holes . The stiffness of the core barrel permits holes to be drilled with less deviation from the intended path , and they are capable of drilling through embedded steel without great effort . On the other hand , where the existing reinforcing must be protected ( e . g ., as in the case of pre-stressing tendons ), this feature of core drilling may be a liability . More importantly , core drills typically produce a very smooth hole that is usually covered with a thin film deleterious to bond . Accordingly , core drilled holes must be thoroughly cleaned prior to injecting adhesive . Note also that some adhesive systems are not suitable for use with core drilled holes . For qualified systems , specific hole cleaning procedures have been developed to optimize bond under these conditions , and are detailed in the Hilti Instructions for Use ( generically , these instructions are known as the Manufacturer ’ s Printed Installation Instructions , or MPII ).
Note : Drilling through existing reinforcing or other embedded objects should in general not be undertaken prior to consultation with the engineer of record or other authority having jurisdiction .
Figure 26 — Core drilling with a hand-held Hilti wet core drill with watercapture technology .
Note : Correct hole drilling and cleaning are critical for the performance of post-installed reinforcing bars . Detailed instructions , referred to by Hilti as Instructions for Use , accompany all Hilti anchoring products . For questions regarding correct installation Hilti offers expert advice through Hilti field representatives , nationwide Hilti Centers , Hilti Customer Service , and online at www . hilti . com ( USA ), or www . hilti . ca ( Canada ).
Figure 28 illustrates the potential influence of drilling method on the load-displacement behavior of a postinstalled reinforcing bar at shallow embedment . Where the drilling method to be used has not been predetermined , it is advisable to use an adhesive that is suitable for all drilling methods ( e . g ., Hilti HIT-RE 500 V3 ).
15 2021