Tendon encapsulation systems are constructed from plastic or galvanised steel materials, and are classified into two main types: those where the tendon element is subsequently bonded to the surrounding concrete by internal grouting of the duct after stressing (bonded post-tensioning); and those where the tendon element is permanently debonded from the surrounding concrete, usually by means of a greased sheath over the tendon strands (unbonded post-tensioning).Casting the tendon ducts/sleeves into the concrete before any tensioning occurs allows them to be readily "profiled" to any desired shape including incorporating vertical and/or horizontal curvature.Higher bond strength in early-age concrete allows more economical fabrication as it speeds production.
Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages. (2000), Self-Compacting Concrete (SCC) Time Development of the Material Properties and the Bond Behavior, Leipzig Annual Civil Engineering Report No. (2003), Prestressed Precast Beams Made of Self-Compacting Concrete, Betonwerk Fertigteil-Technik (Concrete Plant Precast Tech- nology), pp. AASHTO (2004), AASHTO LRFD Bridge Design Specifications, 3rd edition. References AASHTO (1998), AASHTO LRFD Bridge Construction Specifications, 1st edition. (1998), âSelf-Compacting Con- crete in Korea,â Proceedings, International Workshop on Self- Compacting Concrete, Kochi, Japan, pp. CEB-FIP Model Code (1990), Design Code 1990, ComitÃ© Euro- International du BÃ©ton. (2003), âDevelopment of Bond Strength of Reinforcement Steel in Self-Consolidating Concrete.â ACI Materials Journal, Vol. Such deviators usually act against substantial forces, and hence require a robust casting bed foundation system.Straight tendons are typically used in "linear" precast elements such as shallow beams, hollow-core planks and slabs, whereas profiled tendons are more commonly found in deeper precast bridge beams and girders.