ABSTRACT
Durability issues on external tendons were detected in the mid-1990s. Most of these problems were attributable to the cement grout that was used for the corrosion protection. Different strategies were adopted worldwide to specifically deal with these pathologies, with the focus on the filler materials and installation methods: Some regions banned the use of cement grout and promoted the use of soft fillers instead. Other countries made the use of ready-mix formulas mandatory.
In general, new bulletins were published and existing codes were revised to include extended approval and on-site testing methods, while new certification programs for the grout manufacturing plants and the personnel of the application companies were implemented.
These strategies have been further reviewed in the last years to acknowledge and incorporate safety concerns together with the need of a cost-effective inspection and maintenance regime. These safety aspects may ultimately play a major role in selecting the external tendon corrosion protection system.
This paper will not cover internal tendons, for which the industry has developed a series of effective measures to ensure durable post-tensioning, e.g. the use of proper encapsulation of the tendon with polymeric duct, grout quality control methods, or dedicated monitoring systems such as void sensors and electrically isolated tendons.
