ASTM A1081 Evaluating Bond of Seven-Wire Steel Prestressing Strand

Scope:

ASTM A1081 method establishes the standard for prestressing steel strands in pre-tensioned and post-tensioned concrete constructions. The strand bond is impacted by manufacturing processes, subsequent handling, and storage conditions. The bond strength and bond breaker can be determined. Performance and reliability for construction use are studied.

Test Procedure:

In ASTM A1081, six strand samples are withdrawn from a single length and placed in a cylindrical casing with a cement mortar. The strengthened mortar causes the steel-embedded cylinder to land into a tensile testing machine. The tensile force on the loaded end and the displacement of the free end of the strand are determined, and results are drawn.

Specimen Size : 

Six samples of the seven-wire steel prestressing strand with nominal diameters of 0.500 in. (12.7 mm) or 0.600 in. (15.24 mm) are selected from a single continuous length. As per ASTM A1081, each sample should be 800 mm long.

Data:

In ASTM A1081 testing, the tensile force measured on the loaded-end of the strand corresponds with a movement of 0.1 in. (2.5 mm) at the free end of the strand.The load (that is, pull-out force) rounded to the nearest 10 lbf (50 N) is calculated when the free end of the strand has moved down about 2.5 mm into the mortar due to the force applied on the loaded end.

Conclusion:

ASTM A1081 method establishes the standard for prestressing steel strands in pre-tensioned and post-tensioned concrete constructions.