This specification deals with the standard types and grade requirements of seven-wire, uncoated steel strands for use in the construction of pre-tensioned and post-tensioned pre-stressed concrete. The two types of strand are low-relaxation and stress-relieved (normal relaxation). The base metal shall be made of carbon steel and shall undergo stranding and continuous thermal and mechanical treatment. Mechanical testing methods shall be performed to determine the breaking strength, yield strength, elongation, and stress relaxation properties wherein the strand shall conform to the required mechanical attributes of the product. Final products shall be furnished on reels or in reelless packs for packaging and marked with two strong tags for identification. The requirements specified herein shall also be applicable for pre-stressed ground anchor construction.

1.1 This specification covers two types and two grades of seven-wire, uncoated steel strand for use in pretensioned and post-tensioned prestressed concrete construction. The two types of strand are low-relaxation and stress-relieved (normal-relaxation). Low-relaxation strand shall be regarded as the standard type. Stress-relieved (normal-relaxation) strand will not be furnished unless specifically ordered, or by arrangement between purchaser and supplier. Grade 1725 [250] and Grade 1860 [270] have minimum ultimate strengths of 1725 MPa [250 ksi] and 1860 MPa [270 ksi], respectively, based on the nominal area of the strand.

1.2 The values stated in either inch-pound units or SI units are to be regarded as standard. Within the text, the inch-pound units are shown in brackets. The values stated in each system are not exact equivalents; therefore, each system must be used independently of the other. Combining values from the two systems may result in nonconformance with the specification.

1.3 The supplementary requirements in S1 shall be specified for 15.2-mm [0.600-in.] diameter uncoated seven-wire steel strand if needed for applications in prestressed ground anchors.