The document discusses advanced sampling and analysis methods for post-tensioned concrete tendon greases, emphasizing the shortcomings of current testing standards and the need for innovative approaches. It introduces new sampling tools and small volume testing techniques that are more efficient and cost-effective compared to traditional methods. Findings indicate that these new methods may enhance the detection of failure modes and correlate well with established testing procedures.

1. Advanced methods for
sampling and analysis of
post-tensioned concrete
tendon greases
Rich Wurzbach
ASNT Level III, Infrared and Thermal Testing
Laboratory Lubricant Analyst (LLA-I)
MRG Labs, York, Pennsylvania, USA

2. Overview
 Background of tendon grease testing
 Failures of post-tension tendons
 Comparison of as-found conditions,
failures, to routine grease testing
 Root-Cause failure analysis and corrective
actions
 Enhanced sampling methods
 Expanded grease analysis techniques

3. Background
 Some nuclear containment designs
include ungrouted post-tension concrete
tendons
 Tendon sheaths and anchorhead areas
are filled with a corrosion protection
grease
 ASME Section XI, IWL-2525 Table 1
contains guidance for corrosion protection
grease testing, requires 125g sample
minimum

4. Table IWL-2525-1

5. Status of referenced tests
 ASTM D992 was withdrawn in 1983
 Current version of ASTM D4327 allows for
testing of all three ions, but IWL-2525-1
specifies this for nitrates only, requires two other
tests to be performed.
 APHA tests are for environmental and
wastewater; often requires samples being split
between labs, or being run by inexperienced
personnel, may require refrigeration of prepared
sample
 Total alkalinity test does not fall within the scope
of current ASTM standard.

6. Sampling Challenges
 Quantity required for current IWL-2525
test slate requires disassembly of tendon
anchors can, disturbing anchor area
during sampling
 Harvesting of grease may disturb position
of buttonheads, hiding broken strand
indications
 Invasive nature of sampling requires costly
logistical support, equipment, time,
scaffold, etc.

7. Tendon Anchor and Can

8. Containment Tendon Grease
 Tendon failure at US
nuclear power plant
prompts RCFA, CAR
 IWL, Section IX
requires 125g grease
 Test slate for 2 grams
grease developed; tool
for sampling remotely

9. Grease thief and T-handle
 Provide method to sample grease near anchor without
disassembly
 Design consistent with ASTM D7718 Standard
Practice for Obtaining In-Service Samples of
Lubricating Grease
 T-handle and stinger probe allow sampling grease
from face of anchor
 Results from Small Volume Test (SVT) correlated to
disassembly method (large volume sample)
 Sampling saved ~US$500,000 in maintenance costs

10. Water – D95 (IWL-2525)
 Uses distillation glassware
 Per ASTM: “The amount of water as determined
by this test method…to the nearest 0.05 or 0.1
volume%”, which is 500-1000ppm.
 Per Noria Training: D95 “is fairly cumbersome
and requires a comparatively large sample to
ensure accuracy, which is why it is rarely used in
production-style oil analysis labs today”

11. Water – Karl Fischer (SVT)
 Per ASTM: KF allows “direct determination
of water in the range of 10 to 25,000” ppm
 Can be performed on grease via “oven
method” to eliminate interferences and
improve accuracy
 Only a small volume of grease required
(about ¼ gram)

12. Water Testing Comparison
Image courtesy Noria Corporation, USA Images courtesy Metrohm USA
SVT
IWL

13. Total Alkalinity Testing
 Uses an “ASTM Modified” procedure.
 Per ASTM: “determination of acidic or basic
constituents in petroleum products and
lubricants soluble or nearly soluble in mixtures
of toluene and isopropyl alcohol.”
 Per ASTM: “This test method is not suitable
for measuring the basic constituents of many
basic additive-type lubricating oils. Test
Method D4739 can be used for this purpose.”
Visconorust contains basic detergents

14. Total Alkalinty Comparison
 Method developed using 0.5 grams
grease and smaller solvent amount
 Grease fully dissolves, acidification
process followed
 Titration performed with both colorimetric
and potentiometric (D4793) methods,
correlating results
 Titration performed per IWL-2525 and new
small volume method, correlating results

15. Ion testing
 Two of three methods in IWL-2525 allow
for ion-specific electrodes
 New method for small volume ion-specific
electrode method under development
 Can create more repeatable, reliable, and
quicker test for ions, Chloride, Nitrate and
Sulfide

16. SVT Small Volume Test Slate
 Ferromagnetic Iron (ppm) – tested with a Hall-effect
sensor
 Metals spectroscopy – multiple elements, ppm (iron,
calcium, etc)
 Moisture, ppm
 Total Base Number (alkalinity) – using 0.5g sample
 Red oxide count (corrosion particulate by microscope or
direct-imaging sensor
 Die Extrusion Index – evaluating unexpected softening or
hardening of the grease
 Microbial content – quantification of ATP by grease thin-
film extraction

17. Analysis Techniques
Sample is received. fdM+ is run Grease Thief Analyzer is performed and substrate is made
Two strips are used to make
a dilution to run RDE/ICP.
One Strip is used
for FT-IR.
One Strip is Dissolved in Green
RULER solution to run RULER.

18. Ferrographic analysis and Red
Oxide quantification

19. Results
 Data compiled for 500 tendon locations
 Strongest correlation between related
parameters (Calcium and TBN, Red
Oxides and Ferrous Debris)
 Some high Red Oxides were found in
higher Total Alkalinity locations
 Multiple potential failure modes likely
contributor to lack of consistent correlation

20. Results

21. Results

22. Results

23. Results

24. Analysis of Data
 Not a clear single failure mode
represented by correlated data
 Several tendons identified for further
testing: high ATP (microbial), several high
Red Oxides, & high Red Oxide/Low TBN
 Testing showed majority of tendons in
good condition, small percentage
candidates for disassembly and inspection
 Advanced statistics package used for
ranking metrics

25. Analysis of Data
 Dispersion analysis: failed tendon
exceeded 2σ outside the mean for the
failed tendon for three parameters
Data analysis by Dr. David Polk, Polk-Lepson Research, USA http://www.polk-lepsonresearchgroup.com/

26. Analysis of Data
 Regression analysis performed using Red
Oxides as the dependent variable (actual
measure of corrosion) and assigning
weighting factors for scoring
 Failed tendon and one other scored 5, and
twelve others scored as 4.
Data analysis by Dr. David Polk, Polk-Lepson Research, USA http://www.polk-lepsonresearchgroup.com/

27. Summary
 Tendon failure modes require reliable and
cost-effective method for sampling and
analysis
 Using new sampling tools per ASTM
D7718 without tendon can removal
 Small volume testing methods shown to
be equivalent or superior to traditional
testing
 Additional failure modes detectable with
small volume test slate