Tony Barley,

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Tony Barley, Single Bore Multiple
Anchor Ltd, Harrogate, UK Devon Mothersille,
Geoserve Global Ltd, London, UK
Engineering assessment of the grease filled
annulus of sheathed prestressing strand for use
in permanent ground anchorages
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STRAND CORROSION PROTECTION BARRIER
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The annulus should be completely filled with
a corrosion inhibiting compound EN 15372000
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BS 8081 states to fulfil the
recommendations.protective fluids usually aim
to exclude a moist gaseous atmosphere around the
metal by totally enclosing it within an
impervious covering or sheath NOTE
also
applies to bars couplers
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Water leakage from sheathed strands
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Water pouring from wedges prior to capping
O O
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Measurement of volume of greased strand after
withdrawel from sheath
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Greased strand being lowered into a water filled
steel container
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Displaced water volume overflows into measuring
cylinder
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Measurement of internal volume of grease sheath
after strand withdrawel
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Clean grease off outside of strand and grease off
inside of sheath and repeat volume
measurements This establishes volume of the
empty annulus one metre long
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Comparison of the summation volume of grease on
the outside of strand and inside of sheath with
the empty annulus volume determines the
percentage fullness of the annulus
Use of one metre test length as opposed to say
300mm test length reduces degree of error from
end effects
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Evaluation of the volumetric measurement data to
estimate the Fullness of the annulus between
the strand and the inside of the sheath
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3Tests on Strand Type A 92 ,100 ,100
Fullness 3Tests on Strand Type B 82
, 85 , 88 Fullness 3Tests on Strand
Type C 93 , 100 , 94 Fullness 21
Tests on Strand Type D
50 strands less than 50 Full
25 between 50 80 Full
20 between 80 100
Full
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RECOMMENDATION All Suppliers of coated strand
for use in permanent works should carry out
standard tests to demonstrate the adequacy of
their system in achieving complete filling with
a corrosion inhibiting compound Initially it is
recommended that 80 Fullness is the minimum
requirement of the Acceptance Criteria
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RECOMMENDATION Tests should be carried out in
the factory on batch supplies ,and where doubt
exists ,on random samples taken from the
site. Such Requirements and Acceptance Criteria
should be introduced into modern codes Similar
parallel Tests should be considered for bar and
coupler systems
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THANKYOU FOR YOUR ATTENTION TONY BARLEY DEVON
MOTHERSILLE For info see www.theanchorman.com