Product Technical Guides : US-EN Post-Installed Rebar Guide - Page 37

Post-Installed Reinforcing Bar Guide
Sustained tension loading of adhesive anchors has been associated with excessive creep in certain anchor applications . For post-installed reinforcing bar applications , engineering judgment is required to determine whether additional precautions for sustained tension load applications may be required . For specific cases , e . g ., where a small number of bars are subjected to direct tension as a result of dead loads , use of the reduced bond stress check required by ACI 318-19 Section may be appropriate . Additionally , reductions on bond strength for concrete temperature , presence of water ( e . g ., saturated concrete ), and installation in lightweight concrete should be adopted as appropriate .
High-cycle fatigue loading is not specifically addressed in the qualification requirements contained in AC308 . Where high-cycle fatigue loading is relevant for a connection to be performed with post-installed reinforcing bars , contact Hilti technical staff for additional guidance .
SConcrete is a naturally alkaline material and under normal conditions corrosion of embedded reinforcing is prevented by passivation of the bar surface . However , when concrete undergoes carbonation , the decreased pH can lead to incipient corrosion . Furthermore , faster corrosion rates ( pitting corrosion ) are observed if the concrete is contaminated with chlorides .
The qualification of adhesive systems for post-installed reinforcing bar applications includes a specific test for the susceptibility of the system to long-term bar corrosion . Bars installed with qualified systems should exhibit similar corrosion rates to cast-in-place bars in the same concrete . It is important that the adhesive surrounding the bar be relatively void-free to minimize corrosion . Therefore , installation quality is important for corrosion resistance as well as for high bond strength . Contact Hilti technical staff for additional guidance on this topic .
7.3 FIRE
Organic adhesives are affected by high temperatures . For postinstalled reinforcing bar connections that are part of a fire-rated assembly ( floor , roof , etc .) it is important that the fire resistance of the connection be evaluated using test data for the timedependent reduction in bond strength associated with typical geometries and time-temperature loading protocols . Contact Hilti technical staff for additional guidance on this topic .
35 2021