Engineering assessment of the grease-filled annulus of sheathed prestressing strand for use in permanent ground anchorages

The intent of this paper is to briefly review the processes currently adopted to manufacture greased and sheathed strand. The paper also assesses the success of the greasing operations applied to the free length of strand tendons and reports on tests, carried out to investigate the efficiency of greasing, on samples produced by three different manufacturers.

The test work has revealed an unacceptable variation in product quality. Codes of practice recommend that the annulus between the individual strand and the surrounding sheath should be “completely filled with a corrosion inhibiting compound.” Where specialized equipment and factory controlled conditions were employed, the efficiency of grease infilling ranged from 76% to 100%. Investigation of strand greasing from one particular site indicated a range of 0% to 100. A practical acceptance criterion ≥ 80% is recommended and that all sheathed strand suppliers should provide factual data confirming compliance with this criterion that can also be checked routinely in the field.

• Introduction

• Observation

• Greased and Sheathed Strand – the process

• Investigatory Work

• Designated nomenclature and result evaluation method

• Discussion

• Summary and closing remarks

• References