Repair Systems — 02 — Concrete & Structural Defects
Tie wire, bar chairs and formwork fixings
Technical product reference for annealed tie wire, plastic bar chairs and rebar spacers, chemical anchor injection systems, and formwork ties used in concrete spalling repair. Covers product selection for rebar assembly, maintaining minimum cover, starter bar installation, and formwork fixing in Australian remedial repair.
Tie wire, bar chairs and fixings in concrete spalling repair
Reinforcement assembly consumables — tie wire, bar chairs, chemical anchors, and formwork fixings — are the often-overlooked site hardware that holds a concrete spalling repair together during construction. Annealed tie wire positions and secures reinforcement cages; plastic bar chairs maintain the critical minimum concrete cover depth that determines long-term repair durability; chemical anchors provide the structural connection for additional or replacement bars; and formwork ties secure the form panels that contain the fresh repair mortar until it achieves strength.
Product Reference
Individual products — one card each — scroll to view all
National Reinforcing / Generic Supply
Annealed Tie Wire — 1.0 mm / 1.6 mm Galvanised or Black
Annealed soft steel tie wire — rebar tying and formwork fixing
Annealed soft steel tie wire in 1.0 mm and 1.6 mm diameter is the standard site consumable for tying reinforcement bars, binding laps, and fixing bar chairs and spacers in concrete repair formwork. Annealing (heat treatment) makes the wire soft and flexible — it bends easily by hand or with a reo tying tool without breaking, and the tied ends can be twisted and turned back to avoid projecting above the concrete surface. In concrete spalling repair, tie wire is used to secure additional reinforcement mesh or starter bars where reinforcement has been cut or additional bars are being added, to tie replacement cages in column and beam repairs, and to fix bar chairs and spacers at the correct cover depth before placing repair mortar.
Hy-Ten / National Reinforcing / Generic
Plastic Bar Chairs and Rebar Spacers
Plastic bar chairs and rebar spacers — concrete cover maintenance
Plastic bar chairs and rebar spacers are used in concrete repair to maintain the correct minimum concrete cover over reinforcement — this is one of the most critical factors determining the durability of a repair, as inadequate cover over steel leads to rapid carbonation front penetration and re-initiation of corrosion within the repair life. Plastic spacers are used in preference to concrete or masonry nib spacers (blocks) and wire chairs because plastic does not rust and does not create rust staining paths to the mortar surface. Bar chairs are available in heights matching standard cover depths — typically 20 mm, 25 mm, 30 mm, 40 mm, and 50 mm — and in slab, beam, and wall types.
Hilti / Ramset / Fischer
Chemical Anchor — Epoxy or Hybrid Injection System
Injectable chemical anchor — epoxy or hybrid — starter bars and structural fixings
Two-component injectable chemical anchors — epoxy (Hilti HIT-RE 500 V4, Ramset Chemset Epoxy 306, Fischer FIS EM) and hybrid polyester or vinylester (Hilti HIT-HY 200, Ramset Chemset Champion) — are used in concrete spalling repair to install additional reinforcement bars, connect new repair sections to existing structure, fix formwork ties into existing concrete, and provide structural dowels at repair interfaces. The resin is injected into a drilled, cleaned hole using a dual-cartridge dispensing gun — the two components mix in the static mixing nozzle and the combined resin fills the annulus between the anchor bar or bolt and the hole wall. After curing to the time stated in the TDS (varies significantly with temperature — longer at low temperature), the anchor is ready for loading.
Peri / Doka / Generic Supply
Formwork Fixings — Through-Ties, Wing Nuts, and Clamps
Formwork ties, clamps, and cone systems — formwork panel fixings
Formwork fixings — including through-tie bars, wing nuts, clamps, cone systems, and she-bolts — are used to secure plywood and steel formwork panels to the existing concrete structure and to each other during repair mortar casting. In concrete spalling repair, the most common formwork fixing configurations are: (1) through-tie systems in column and wall forms where the tie rod passes through the existing wall and is threaded through both form faces and secured with wing nuts or clamp plates; (2) she-bolt and cone systems that leave no permanent hole through the finished concrete face — the cone is removed on stripping and the she-bolt is unscrewed, leaving only a small cone-shaped hole that is filled with repair mortar; and (3) form clamps (C-clamps, snap ties) used where through-ties cannot be used — for example, on single-face wall forms where access to the back face is restricted. In many remedial repair situations, through-ties are not possible because drilling through the existing structure would damage it or compromise waterproofing — in these cases, surface-fixed form props and external clamps supported by chemical anchor fixings into the existing concrete are used instead.
System Comparison
Concrete spalling — confirm all selections against the current manufacturer TDS before specifying.
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Do not confuse tie wire, bar chairs and fixings with:
- Structural connections — tie wire is a temporary positioning aid only and provides no structural load transfer — for any structural connection between new and existing concrete (shear keys, starter bars, stitching bars), use chemical anchors designed to AS 5216 or mechanical fasteners engineered to AS 4100
- Concrete mortar block spacers — small mortar blocks used as rebar spacers are an alternative to plastic bar chairs but are porous and can become corrosion initiation points in aggressive environments — use plastic bar chairs in remedial repair work
- Mechanical expansion anchors — torque-controlled and drop-in expansion anchors are different from chemical injection anchors — mechanical anchors are used in uncracked concrete for static loads; chemical anchors are generally preferred in cracked concrete, near edges, and for rebar installation
- Scaffold tube and coupler fixings — scaffold tube and coupler connections are for access platforms, not for structural formwork fixing — do not use scaffold couplers as primary form tie fixings unless specifically engineered for that purpose
- Helical crack stitching bars — proprietary stainless helical bars grouted into slots across cracks (Helifix, Thor Helical) are a specialist crack stitching product, not the same as general-purpose tie wire or chemical anchor starter bars — listed under settlement cracks and cracking repair systems
Disclaimer
This page provides general technical information only. Final product selection must be confirmed against the current manufacturer technical data sheet, project specification, substrate condition, exposure classification, AS 3600 requirements, and applicator warranty conditions. Do not rely on this reference as a substitute for professional engineering or remedial building consultant advice.