Prestressing Strand & Wire
Prestressing strand and wire are widely used both for the in-situ pre-or post-stressing of large concrete structures such as bridges and nuclear reactors, and for prestessing of prefabricated concrete elements such as beams. These materials are some of the highest strength constructional steels in use today, and get used in some of the most high-profile and critical engineering structures. They derive their strength from a combination of their chemistry (high carbon, microalloy), and cold work imparted through the extensive hot and cold reduction they acquire in the manufacturing process. Some products may have their strength achieved by a heat treatment process.
Prestressing strand and wire products are covering by BS 5896:2012, and can be covered by the UK CARES scheme for product certification. Testing of these materials requires special grips and extensometry to meet the specified requirements. Test methods for prestressing steels are specified in BS EN ISO 15630-3:2010. R-Tech’s scope of accredited testing of wire and strand products according to these standards includes the following:
Tensile testing to 1500kN
Fatigue testing to 400kN
Reverse bend testing
In addition, testing can be performed to most national and international standards.
Prestressing bars are also available on the market. These are also used in post-tensioning of bridge decks (for example), or may be used as high strength tension elements in buildings. These are generally alloy steels, and again may achieve their strength through a combination of chemistry, cold work and heat treatment.