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Factors Affecting Bond and Friction Losses in Multi-Strand Post- Tensioning Tendons Including the Effects of Emulsifiable Oils

T. Lüthi, J. Diephuis, J. J. Icaza, J. E. Breen, and M. E. Kreger

2005

Emulsifiable oils are often used in post-tensioned construction to reduce friction losses and to provide temporary corrosion protection for tendons during the period of time between stressing and grouting. In the past, oils were flushed from the ducts with water prior to grouting. This practice often led to voids in the grout and created environmental problems related to the disposal of the flushing water.

This report is a summary of research done at Pennsylvania State University and The University of Texas at Austin that addressed the effect of unflushed emulsifiable oils on corrosion, bond, and friction losses. Certain oils available on the market do provide adequate temporary corrosion protection. Bond test results indicate that the strength of post-tensioned specimens with oiled tendons is similar to or better than the strength of specimens with unoiled tendons. Specimens with oiled tendons did experience large amounts of slip in comparison to specimens with unoiled tendons. Friction tests indicate that lubrication reduces the friction coefficient in rigid steel pipes and HDPE ducts on the order of 15 percent if the tendon is stressed when the oil is fresh. The coefficient of friction for HDPE ducts measured from this test program was significantly less than the value recommended by AASTHO.

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