Can they drill it out or does it need to move? Are there recommendations for drilling out?
Hi Kathy,
Ultimately, the decision on whether and how to drill out the cast-in anchor or to abandon it is at the discretion of the engineer of record, but below are some considerations.
An option to consider is to core drill out the existing anchor and replace it with a larger adhesive anchor system. Care should be taken for the drill to be as concentric as possible with the existing anchorage. The new anchorage would need to follow the installation requirements (minimum anchor spacing, edge distance, concrete thickness, etc. All available in our Anchor Fastening Technical Guide) for the adhesive anchor. Depending on your base material, two of Hilti’s ultimate performing chemical anchor systems are the HIT-HY 200 V3 and HIT-RE 500 V3. If maintaining the original anchor’s diameter with the larger core-drilled hole, the HIT-RE 500 V3 Technical Bulletin for HIT-RE 500 V3 with Large Annular Gap includes additional data for the engineer to consider.
For abandoning the anchor, Hilti does not have test data regarding the effects of abandoned anchor bolts near a newly installed (mechanical or adhesive) anchor. However, please reference the attached University of Tennessee “Effect of Abandoned Holes on Capacity of Wedge Bolts” study for your review. Page 6 contains a summary of the report findings.
Please reach out to hnatechnicalservices@hilti.com if you have additional questions.
Best,
Sinan