Doug Neely, PE AASHTO Technical Subcommittee for Movable ...
AASHTO Subcommittee on Materials...
Transcript of AASHTO Subcommittee on Materials...
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Concrete CTE
AASHTO Subcommittee on Materials Conference
Anchorage, Alaska August 2 - 7, 2009
Suneel Vanikar FHWA, Office of Pavement Technology (202) 366-0120 [email protected]
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CTE Impact on Pavement Performance
Early-age cracking (high CTE vs high slab restraint)
Transverse/longitudinal cracking due to curling stresses
Faulting (built-in curl, joint opening, curl)
Joint spalling (excessive jt movement with high CTE)
Crack spacing/width for CRCP (LTE and punchout)
Edge punchouts (due to curl)
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122°F
50°F
0.0059
CTE=length change/unit length/degree
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122°F
50°F
0.0033
CTE=length change/unit length/degree = 0.0026 in / 7.0 in / 72 F = 5.1 microstrain/F
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Custom Built CTE Device
304 Stainless Steel
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AASHTO TP 60-00
Typical frames made from invar or stainless steel
Typical calibration bar made from 304 stainless steel per TP 60 recommendations
CTE of 304 SS stated as 17.3 x10-6/oC in TP 60
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Independent Lab Result for 304 SS
Specimen ID
Avg.CTE(ppm/oC) (50o to 10oC)
Alumina bisque 5.4+/-0.1
304 Stainless Steel - Gilson reference bar 16.2+/-0.1
Titanium 8.9+/-0.1
304 Stainless Standard - Pine reference bar 15.9+/-0.1
410 Stainless Steel 10.4+/-0.1
304 Stainless Steel – TFHRC manual unit 15.8+/-0.1
Precision Materials and Instruments Corporation
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Impact of Revised CTE Values
LTPP Database AASHTO TP 60 Test Method MEPDG Models in version 1.0 Testing Results from Other Labs
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Standard Method of Test for Coefficient of Thermal Expansion of Hydraulic Cement Concrete AASHTO Designation: T 336-09
The test procedure described in Section 7.2 is used to determine a correction factor to account for expansion of the measuring apparatus during the test. A calibration specimen with a known coefficient of thermal expansion should be used . The specimen should be composed of a material that is essentially linearly elastic , noncorroding, non-oxidizing, non porous and nonmagnetic, and it should have a known thermal coefficient as close as possible to that of concrete e.g. a range of 9 to 18 x10-6/oC within the temperature range of 10 to 50 oC (304 stainless steel is a suitable material) An ISO 9001 or equivalent laboratory should determine the CTE of the calibration specimen according to ASTM E 228 or ASTM 289 within the temperature range of 10 to 50 oC and provide a certificate of the CTE value including the lot number of the sample tested.
NOTE: When using version 1.0 of the MEPDG software, AASHTO TP 60-00 (2007) should be used.
Section X2.1
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Effect of CTE on the predicted percent of slabs cracked
Effect of CTE variability of Concrete Pavement Performance as predicted using the Mechanistic - Empirical Pavement Design Guide, Jussara Tanesi, M. Emin Kutay, Ala Abbas, and Richard Meininger, Transportation Research Board 2007.
(6.3 oC) (8.1 oC)
(9.9 oC) (11.7 oC)
(13.5 oC) (15.3 oC)
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Ongoing/Planned Activities
Update LTPP Database (Aug 2009) Update AASHTO 336 (May 2009) Briefings
Joint Technical Committee on Pavements (May 2009) DARWin-ME Task Force (June 2009)
Recalibrate MEPDG Models (winter 2009) JTCP drafting research problem statement for 20-7
funding (Aug 2009) FHWA Activities
Memo to field (Aug 2009) Draft white paper (Aug 2009) CTE inter-lab study- 17 labs (Aug 2009) CTE ruggedness study (summer 2010) Presentations at several TRB concrete/design
committees (Jan 2010)
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Recommendations
MEPDG version 1.0 use TP 60 CTE values MEPDG version 1.x or version 2.0 use T 336 CTE
values Local Calibration
Completed – verify after national recalibration of models (version 1.x or 2.0)
in process- delay determination of calibration coefficients until national recalibration of models (version 1.x or 2.0)
Correction factor to adjust CTE values is
difference between assumed and actual CTE of calibration specimen
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Summary
Current CTE research still valid MEPDG ver 1.0 or ver 1.x - use CTE
based on TP 60 (17.3 x10-6/C for 304 SS)
MEPDG ver 2.0 - use CTE based on new AASHTO Test Method (T 336) and 2009 recalibrated models
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Additional Information
For additional CTE information contact: Gary Crawford Federal Highway Administration Phone: (202) 366-1286 e-mail: [email protected]