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Increased demand leads to increased availability
Consulting engineers, government agencies, and other parties frequently query the technical staff at the Concrete Reinforcing Steel Institute (CRSI) on the differences between the ASTM A 706/A 706M specification1 for low-alloy steel reinforcing bars and the ASTM A 615/A 615M specification2 for carbon-steel reinforcing bars. The aim of this article is to:
* Compare the major requirements in ASTM A 706/A 706M with provisions in ASTM A 615/A 615M;
* Relate current availability and relative costs of low-alloy steel reinforcing bars (A 706 bars); and
* Offer insight into prospective near-term developments and issues.
HISTORY OF A 706 BARS
The first version of ASTM A 706 was published by ASTM International in 1974. An interesting description of its background and development is included in a 1973 report by ACI Committee 439.3 The specification was developed in response to the engineering community's requirements for reinforcing bars with controlled tensile properties for earthquake-resistant structures and controlled chemical composition for weldability. In 1986, the specification was revised into a combined standard containing both in.-lb and SI units, and the new designation became ASTM A 706/A 706M.
In 1990, CRSI published Report No. 34, "ASTM A 706 Reinforcing Bars-Technical Information with Commentary on Usage and Availability."4 Prepared by the CRSI technical staff, this report was a response to questions raised by architects, engineers, contractors, and state and federal government agencies. The 1991 article titled "Questions and Answers on ASTM A 706 Reinforcing Bars"5 was based on this CRSI publication and reported that the demand for weldable bars in cast-in-place construction had never fully materialized. Starting in January 1995, however, the California Department of Transportation (Caltrans) initiated a policy of requiring A 706 bars for virtually all of their reinforced concrete structures. Carbon-steel reinforcing bars conforming to ASTM A 615/A 615M would only be permitted for use in slope and channel paving, minor structures, sign and signal foundations (pile and spread footing types), roadside rest facilities, certain types of concrete barriers, and temporary railing.
In November 2005, the Illinois Department of Transportation (IDOT) implemented a policy requiring the exclusive use of A 706 bars for all reinforced concrete construction. IDOT's requirements are even broader than those of Caltrans. For example, IDOT requires A...