unbondend prestressed concrete steel strand 1. Diameter: 6.35-15.24 ... 1x7. 3. Strength Grade: 250/270 unbondend prestressed concrete steel strand,suitable for cast-in-placeconcrete of long-span ... 10000 Metric ton / month4, the certification we have: Norway, UK, Australia, South Korea, Germany, Malaysia, Thailand, ISO 9001; ... Specified min.breaking strength3.5 unbondend prestressed concrete steel strand