Influences of Anticorrosive Grease Layer on the Bonding Performance of the Anchor Cable–Grout Interface

Abstract

To investigate the influence of grease residue in the anchorage section of unbonded steel strands on the bond performance of the steel strand–cement grout interface, pull-out model tests of steel strands were conducted. Four test conditions were considered: grease-free, uncleaned, water-cleaned, and cleaning-agent-cleaned. A total of eight steel strand pull-out tests were completed. The effects of different grease treatment methods on interfacial bond performance were analyzed in terms of load– displacement curves, peak pull-out force, bond strength loss rate, and cumulative energy dissipation. The results show that grease residue significantly weakens the interfacial bond performance between the steel strand and cement grout. Under greased conditions, the peak pull-out force was only 17.8%– 29.9% of that under the grease-free condition, indicating a significant loss of bond strength. Under the non-disassembled cleaning condition, cleaning-agent treatment produced a certain recovery effect on the interfacial bond performance, with an average peak pull-out force of 4.70 kN, which was higher than that of the uncleaned condition, but still only recovered to 29.9% of the grease-free condition. The peak pull-out force under the water-cleaned condition was only 2.80 kN, even lower than that of the uncleaned condition, indicating that simple water rinsing could not effectively remove grease residue from the gaps between steel wires and might instead cause the grease to form a more continuous lubricating film on the surface of the steel strand. Therefore, for the anchorage section of unbonded steel strands, surface cleaning without disassembling the strand is insufficient to effectively restore the interfacial bond performance. In practical engineering, thorough removal of grease from the anchorage section should be given sufficient attention.