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OCR for page 29
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Table 8. Regression coefficients for model based Corrosion Potential, and as Table 12, which was developed for
on Contact Angle Measurement after Lime Dip & the model based on the combination of Contact Angle Mea-
Change in Corrosion Potential. surement after Lime Dip & Organic Residue Extraction for
those residues determined to be stearate only.
Predictor Coefficient
Constant 1.209 Using Table 11 as the example, the first row shows the re-
Contact Angle after Lime Dip (°) -0.007 sults of these two individual QC tests obtained for Source 349.
Change in Corrosion Potential after 6 h (V)--as Received 1.233 Based on the regression model, the predicted mortar pull-out
Adjusted Coefficient of Determination (R2 adj.) 0.73 stress at 0.1-in. slip is 0.264 ksi. The lower bound on the pre-
diction interval for that combination of the two test results
Table 9. Regression coefficients for model based on must be calculated specifically using those values and is
Contact Angle Measurement after Lime Dip & Organic 0.131 ksi. Since 0.131 ksi is less than the mortar pull-out
Residue Extraction (stearate-based residues). threshold of 0.313 ksi, this source fails to meet the minimum
Predictor Coefficient
threshold for the combined Contact Angle Measurement
Constant 0.864 after Lime Dip & Change in Corrosion Potential performance.
Contact Angle after Lime Dip (°) -0.006 For Source 548, the lower bound on the prediction interval
Extracted Organic Residue (mg/cm2) -1.093 calculated for the specific combination of test results measured
Adjusted Coefficient of Determination (R2 adj.) 0.98
for that source is 0.420 ksi, and this source "passes" since this
value exceeds the 0.313 ksi threshold. The last column shows
Table 10. Regression coefficients for model based whether that strand would be expected to pass based on the
on Weight Loss on Ignition (LOI), Contact Angle actual pull-out test result. The conclusions reached based on
Measurement after Lime Dip & Change in Corrosion the prediction interval and the actual pull-out test results are
Potential. consistent for Sources 349 and 548. However, this is not always
Predictor Coefficient the case; the evaluation process based on the prediction inter-
Constant 1.203 val is by definition conservative, and some sources will be
Weight Loss on Ignition (mg/cm2) -0.846 judged as failing that may not fail in the actual pull-out test.
Contact Angle after Lime Dip (°) -0.006
A similar example is shown in Table 10, which was developed
Change in Corrosion Potential after 6 h (V)--as Received 1.178
Adjusted Coefficient of Determination (R2 adj.) 0.76
for the model based on the combination of Contact Angle
after Lime Dip & Organic Residue Extraction (for stearate-
based residues).
lower bound on the prediction interval, and the comparison of
the lower bound and the actual pull-out test result with the
Interpretation of Elemental Analyses
specified mortar pull-out threshold of 0.313 ksi, for two of the
Relative to Manufacturing Processes
three multiple regression models. These are shown as Table 11,
which was developed for the model based on the combination The atomic absorption and colorimetric analyses of wash
of Contact Angle Measurement after Lime Dip & Change in solutions from strands from various sources indicated varied
Table 11. Evaluation of prediction interval for model based on Contact Angle
Measurement after Lime Dip & Change in Corrosion Potential.
Mortar Pull-Out 0.1-in Slip Stress (ksi)
Contact Pass/Fail*
Pass/Fail*
Strand Angle Change in Value Based on
Experimentally Lower Bound Based on
Source after Corrosion Predicted by Prediction
Determined in of Prediction Pull-Out Test
ID Lime Potential (V) Regression for Interval from
Pull-Out Test Interval Result
Dip (°) QC Results QC Tests
349 87 -0.289 0.156 0.264 0.131 Fails Fails
548 79 -0.080 0.623 0.576 0.420 Passes Passes
697 68 -0.154 0.606 0.559 0.417 Passes Passes
717 94 -0.241 0.206 0.276 0.136 Fails Fails
478 73 -0.272 0.409 0.38 0.232 Fails Passes
960 76 -0.211 0.409 0.435 0.303 Fails Passes
102 87 -0.266 0.315 0.291 0.161 Fails Passes
103 79 -0.172 0.397 0.463 0.331 Passes Passes
151 98 -0.322 0.273 0.149 0.003 Fails Fails
* Threshold for passing is 0.313 ksi.
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Table 12. Evaluation of prediction interval for model based on Contact Angle
Measurement after Lime Dip & Organic Residue Extraction (100% stearate only).
Mortar Pull-Out 0.1-in Slip Stress (ksi)
Contact Pass/Fail*
Extracted Pass/Fail*
Strand Angle Value Based on
Organic Experimentally Lower Bound Based on
Source after Predicted by Prediction
Residue Determined in of Prediction Pull-Out Test
ID Lime Regression for Interval from
(mg/cm2) Pull-Out Test Interval Result
Dip (°) QC Results QC Tests
717 94 0.117 0.206 0.211 0.176 Fails Fails
478 73 0.033 0.409 0.420 0.388 Passes Passes
960 76 0.035 0.409 0.401 0.371 Passes Passes
102 87 0.069 0.315 0.303 0.274 Fails Passes
151 98 0.037 0.273 0.276 0.240 Fails Fails
* Threshold for passing is 0.313 ksi.
levels of sodium, calcium, potassium, zinc, boron, and phos- are zinc phosphate and sodium borate, also known as borax.
phate on the strand samples. The presence and concentration Lubricants typically consist primarily of either sodium stearate,
of these elements is largely governed by the specific pre- calcium stearate, or some other fatty acid blend.
treatment process and wiredrawing lubricants used in the Tables 13 and 14 show each strand source ranked in ascend-
manufacturing of strand from each specific source, although ing order of concrete or mortar pull-out bond performance
other sources of some of these elements may also be involved. together with the prominent elements removed during the
The pretreatments commonly used in strand production extraction process, and the presumed pretreatment and
Table 13. Compounds likely used in manufacture of each
source--historic and recently manufactured strands.
Concrete Pull-
Prominent Presumed Presumed
Strand out Bond
Elements Pretreatment Lubricants
Stress (ksi)
calcium salt of
153 Ca, Zn, P zinc phosphate -
fatty acid
KSU-H Na, K, B borax Na/K stearate 0.209
SC-F Ca, Zn zinc phosphate calcium stearate 0.223
101 Na, K, B borax Na/K stearate 0.241
KSU-F Na, K, B borax Na/K stearate 0.241
102 Na, Ca, B borax Na/Ca stearate 0.441
SC-H Na, K, Zn zinc phosphate sodium stearate 0.472
151 Na, B borax calcium stearate 0.541
sodium salt of
SC-IS Na, Zn zinc phosphate 0.682
fatty acid
sodium salt of
103 Na, Zn zinc phosphate 0.944
fatty acid
Table 14. Compounds likely used in manufacture of each
source--OSU strands.
Mortar Pull-
Prominent Presumed Presumed
Strand Out Bond
Elements Pretreatment Lubricants
Stress (ksi)
calcium salt of
349 Ca, Zn, P zinc phosphate fatty acid and 0.156
resin
717 Na, Ca, Zn, P zinc phosphate Na/Ca stearate 0.206
478 Na, K, Zn, P zinc phosphate Na/K stearate 0.409
960 Na, K, Zn, P zinc phosphate Na/K stearate 0.409
calcium salt of
697 Ca, Zn, P zinc phosphate fatty acid and 0.606
resin
Na/K salt of fatty
548 Na, K, Zn, P zinc phosphate 0.623
acid
