5　Materials and Equipment

5.1　Prestressing Strand

5.1.1　Prestressing strands consist of high-strength low-relaxation strands with or without coating.They may be of standard type or die drawing type 1860 MPa（Class 270），1960 MPa（Class 290）.Each steel wire of the strand shall not have a joint in full length.

5.1.2　The appearance of strands shall be checked against the following requirements：Intact external packing；Free of oil stain，rust，burr and damage on surface；Diameter tolerance within±0.15 mm；Twisting distance is 12～16 times the diameter for standard type and 14～18 times for die drawing type；Good elongation performance without disheveled end；No damage on PE cladding.The strands shall not be allowed into storage unless they pass the appearance inspection，and detailed records shall be made accordingly.

5.1.3　The supplier（manufacturer）shall provide material certificate，certificate of compliance and test report for each bundle of strand.For unbonded prestressing strand，the material certificates for high density polyethylene resin and special anti-corrosive lubricating grease shall be provided.

5.1.4　The mechanical properties of strand shall comply with the provisions of GB/T 5224.

5.1.5　The mechanical property test of a strand shall cover tensile strength，yield strength，elongation，relaxation performance and elastic modulus.The tests for relaxation performance and elastic modulus shall be carried out by manufacturers and the test results shall be provided along with each delivery.Other test items shall be made by construction contractors as per Appendix A.

5.1.6　The PE cladding surface of unbonded and retard bonded strands shall be even and smooth，free of crumple，crack，oil leakage and unplasticized particles.The defects mentioned above shall be properly remedied.The material of PE cladding shall conform to relevant standards and recycled materials shall not be used.

5.1.7　The anti-corrosive grease for unbonded strand shall have eligible physical properties and proper chemical stability，and contain no harmful ingredients.The applied amount shall be not less than 50g/m.The PE cladding shall be not less than 1.0mm in thickness and have proper toughness and rigidity，and resistant to corrosion and aging.

5.1.8　The curing time of adhesive shall be indicated on the retard bonded strand.

5.1.9　Prestressing strands of the same classification，type，size and process should be used for the same construction location in a prestressing works.Relevant tests and verifications shall be performed when an alternative prestressing strand is required.

5.1.10　The PE cladding of unbonded and retard bonded strands shall be protected during lifting，handling and storage to avoid being impacted and damaged.In addition，measures against rain，sunlight，pollution and corrosion shall be taken.