Post-Installed Rebar with Chemical Anchors: A Practical Guide
Post-installed rebar means fixing new reinforcement bars into existing concrete using an injection mortar. It is used when a building is extended, strengthened or modified – adding columns, slabs, staircases, beams or lift cores to an existing structure.
Where it is used
- Extending slabs, beams and walls.
- Adding new columns, staircases and lift shafts.
- Retrofitting and strengthening older buildings.
- Correcting missed or wrongly placed starter bars.
Which mortar to use
Use an injection mortar approved for post-installed rebar, typically an epoxy such as Hilti HIT-RE 500 V4 or Fischer FIS EM Plus. Bar size, embedment length and spacing must come from the structural engineer’s design, not from rule of thumb.
Installation steps
- Mark and scan to avoid cutting existing reinforcement.
- Drill to the specified diameter and full depth, keeping the hole straight.
- Clean thoroughly: blow, brush, blow – repeated as per the system instructions. This is the most important step.
- Inject from the bottom of the hole with an extension tube and piston plug for deep holes, filling about two-thirds.
- Insert the bar with a slow twisting motion to the marked depth; mortar should show at the hole mouth.
- Cure for the full time on the cartridge before loading or concreting – longer in cold weather.
Common mistakes
- Dusty holes – the biggest cause of weak bond.
- Using a general-purpose mortar not approved for rebar.
- Embedment shorter than the design.
- Air pockets in deep holes when no piston plug is used.
- Loading or vibrating before full cure.
Check the work
For important structural work, consultants often ask for a pull-out test on sample bars. Fasteners King can supply the mortar, accessories and on-site testing.
Frequently asked questions
Can I use any chemical anchor for rebar?
No. Use a mortar whose approval covers post-installed rebar for your bar size, and follow the engineer’s design.
How long before I can concrete over new rebar?
After the full cure time printed on the cartridge, which depends on base-material temperature.
Where can I buy rebar anchoring systems in Delhi?
From Fasteners King, Chawri Bazar, Delhi – chemical anchors in Delhi NCR – or our Guwahati branch. Call +91 90057 00569.