Two ASTM International specifications dominate carbon-steel reinforcing bar in North America. ASTM A615/A615M is the general-purpose standard; ASTM A706/A706M is the low-alloy, controlled-chemistry standard written for weldability and seismic performance.
The core difference is chemistry. A706 places maximum limits on carbon, manganese, phosphorus, sulfur and silicon — plus a carbon-equivalent cap — so the bar can be welded without cracking and can deform ductilely under seismic load. A615 limits phosphorus only, which makes it harder to weld reliably.
Practical guidance: specify A706 where the structure is in a seismic zone or where rebar will be welded; A615 is economical for general reinforcement where neither applies. Many drawings simply call up 'A706 where welding or seismic detailing is required, A615 otherwise.'
Whichever bar grade a project uses, the tie wire, bar ties, chairs and mesh around it still have to meet their own specifications. Leeter supplies black-annealed and galvanized tie wire, welded mesh to ASTM A1064 and rebar supports matched to the specified cover — send your drawing and we will match the accessories.
