Product Technical Guides : US-EN Post-Installed Rebar Guide - Page 18

Post-Installed Reinforcing Bar Guide
Bond strength [ N / mm 2 ]
18 16 14 12 10 8 6 4 2 0
Compressed air drilling
Hammer drilling
Diamond drilling
Displacement [ mm ]
Figure 28 — Example of the influence of drilling method on the bonddisplacement behavior of a post-installed reinforcing bar installed with an adhesive not suitable for diamond drilled holes .
3.5 HOLE CLEANING h ef = 10d a f ' c ~ 3000 psi
1 2 3 4 5
Bond between adhesive and concrete is directly influenced by the condition of the hole wall at the time of adhesive injection . The concrete in which the post-installed reinforcing bar is to be installed may be dry , saturated or even partially or completely submerged at the time of installation .
Figure 30 — Hilti extension rod and Hilti HIT-RB matched tolerance steel brushes for hole cleaning .
All cleaning procedures finish with the use of compressed air . ( It is important to note that the use of compressed air may produce flying debris — eye protection should be worn at all times .)
The importance of hole cleaning as specified in the Hilti Instructions for Use for the performance of post-installed reinforcing bars is indicated in Figure 32 . For cases where adherence to multi-step hole cleaning procedures may not be possible , use of Hilti SafeSet™ technology with Hilti Hollow Drill Bits ( HDB ) is recommended .
Note : Where installation in water-saturated or submerged concrete is required , check that the adhesive system to be used is qualified for these conditions .
Wet diamond core drilling will necessarily result in a damp environment in the drilled hole . Hole cleaning generally involves a water-cleaning process , followed by sequential blowing out the hole with compressed air ( Figure 29 and Figure 33 ) to remove debris and water , and the use of a wire brush ( Figure 30 ) to mechanically scour the hole wall .
Figure 31 — Hilti SafeSet™ System with Hollow Drill Bit ( HDB ) and vacuum .
Compressed air nozzle Hose extension hole cleaning in accordance with MPII
reduced cleaning effort
no brushing ( compressed air only )
Blow out tool
Figure 29 — Hilti accessories for compressed air hole cleaning operations ( partial ).
Bond stress no cleaning
Figure 32 — Schematic representation of the potential influence of hole cleaning procedures on the measured bond and displacement of a postinstalled reinforcing bar loaded in tension .
16 2021