Product Technical Guides : US-EN Post-Installed Rebar Guide - Page 20

Post-Installed Reinforcing Bar Guide
The objective of adhesive injection is to achieve a void-free installation . Aside from reducing bond area and inhibiting cure , air voids in the injected adhesive may lead to increased effort associated with bar installation and can cause uncontrolled ejection of the adhesive from the hole during bar installation as air is forced out of the adhesive matrix .
Note : Proper skin and eye protection should always be worn during injection of Hilti adhesives .
In order to inject the adhesive with minimal air voids in drilled holes , the Hilti injection system utilizes matched-tolerance piston plugs ( Figure 36 ). The Hilti piston plug system provides positive feedback to the operator for controlling the injection process through the pressure of the adhesive on the plug and has been shown to dramatically improve injection quality and efficiency .
Smaller bar diameters can be inserted in a vertical downward direction with ( relatively ) minimal effort . Large-diameter bars in horizontal and upward-inclined orientations may require substantial effort to lift and insert the reinforcing bar into the adhesive-filled hole ( Figure 38 ). In all cases , it is advisable to test the fit of the bar in the hole prior to injecting adhesive .
For overhead installations , particularly of larger diameter bars , provision must be made for securing the bar during adhesive cure . In addition , certification requirements for installers performing installation of bars to carry sustained tension loads , as well as additional special inspection requirements , may apply .
Note : Hilti dispensers provide efficient , void-free adhesive injection at all orientations , hole diameters and depths , and temperature conditions .
Figure 36 — Hilti HIT-SZ piston plugs , available in diameters appropriate for # 3 through # 18 reinforcing bars .
Dispensing equipment used for injection is generally selected as a function of bar size and orientation , ambient temperature conditions and accessibility ( Figure 37 ).
Figure 38 — Installing large diameter bars .
Figure 37 — The Hilti HIT-P8000D pneumatic dispenser , appropriate for large volume installations and large bar diameters .
18 2021