Rationale

ASTM A722 has long been a process specification, requiring that bar be "subjected to cold-stressing to not less than 80% of the minimum tensile strength, and then shall be stress-relieved, to produce the prescribed mechanical properties." This process controls stress relaxation, however, there is no relaxation threshold in A722. Recent advances in stress relaxation testing have allowed the relaxation of bars that meet this process requirement to become available. Since stress relaxation is an important tensile property for many prestressing steel applications, this ballot item proposes to add a relaxation threshold requirement. Additionally, there are other processes that may be employed to reduce stress relaxation, so this ballot proposes to make the cold stress/stress relief process non-mandatory. Since there is no current procedure for testing relaxation of prestressing steel bar, this ballot item also proposes to add testing procedures. Finally, an informational note is proposed to let designers know there are bars available in the market with lower relaxation values than the specified threshold. It is important to note that Ballot Item A01.05 (23-02) Item 3 was previously balloted and many negative votes were received, and the technical contact has been unable to resolve those negatives. This ballot represents an alternative to that ballot.