Geo Strap Strain

Q: We are using a 40kN polyester-coated strap for mechanically stabilized wall reinforcement. We sent the strap to a third-party laboratory for quality assurance testing, and they reported an ultimate tensile strength of 20kN (half of the project specification) and a strain at rupture of greater than 50%. Can you offer a suggestion on how to remedy the situation?

A: First of all, are you using an accredited lab? Secondly, Geo straps have a strain at rupture of less than 15%, so something appears off. These high strength reinforcement materials generally are tested with roller grips accompanied by extensometers. The grips can’t initiate failure, and the rupture needs to occur within the specimen gauge length. I would interrogate the lab and get pictures of the test setup and ruptured specimens before ordering new material.