Corrosion on prestressing wires due to segregation of the injection mortar – Detection of injection defects with Ultrasonic-Echo Technique

Abstract

Unsuitable granulometry of injection mortar can promote segregation if high hydrostatic pressure impacts on the mortar for longer time during hardening. Endangered for segregation are long perpendicular prestressing tendons e.g. used in high towers due to the high hydrostatic pressure inside. The segregation causes an accumulation of water and solved ions on top of the tendons. In this area an extremely high pH-value and a very low electrochemical potential occurs. This environment is extremely corrosive and can cause wire breaks within only few months. With the Ultrasonic-Echo Technique (Flaw Detectors) it is possible to detect injection defects by using the phase shift technique.