Determination of Creep Compliance and Tensile Strength of Hot-Mix ...

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ACKNOWLEDGEMENTSThe authors wish to thank the Missouri Department of Transportation (MoDOT), andin particular, John Donahue for sponsoring this work, and Leslie Wieberg forpreparing the specimens. Special thanks go to Harold Von Quintus of AppliedResearch Associates, Donald W. Christensen and Ray Bonaquist of AdvancedAsphalt Technologies, George Lopp, assistant-in-engineering at the University ofFlorida at Gainesville, Y. Richard Kim of North Carolina State University, MihaiMarasteanu of the University of Minnesota, William Buttlar of the University of Illinoisat Champagne-Urbana, James Sherwood and Raj Dongre of the Federal HighwayAdministration, and Ayesha Shah of the North Central Superpave Center, all ofwhom contributed guidance on the work in this study.EXECUTIVE SUMMARYCreep compliance and indirect tensile (IDT) strength of hot-mix asphalt (HMA) arethe two primary inputs to the low-temperature or thermal cracking module in the newMechanistic-Empirical Pavement Design Guide (M-E PDG) software. Creepcompliance is defined as time-dependent strain per unit stress, while IDT strength isbest defined by what its name implies: HMA strength when subjected to tension.The test protocol used as the reference for this work is American Association ofState Highway and Transportation Officials (AASHTO) test method T 322. Howeverin preparation for the laboratory work that was performed at the Missouri Universityof Science and Technology (Missouri S&T), many experts (see Acknowledgements)were consulted as to how IDT creep/strength testing and calculations are actuallybeing performed.MoDOT supplied the test specimens. Six different plant-produced wearing (surface)course mixes were tested. Four of the mixes were tested at three levels of percentair voids: 4, 6.5, and 9%. The remaining two mixes were tested only at 6.5% airvoids. Per requirements of the M-E PDG, creep testing was performed at 0, -10, and-20 degrees Centigrade (°C) (32, 14, and -4 degrees Fahrenheit (°F), respectively)and IDT strength testing was performed at -10°C. Additional IDT strength testingwas performed at 4.4 and 21°C (40 and 70 °F, respectively) per MoDOT’srequirements. Poisson’s ratio was determined from the creep testing while tensilefailure strain was determined from the IDT strength testing.All required results were obtained. Trends such as increasing creep compliance anddecreasing tensile strength with increasing % air voids and/or temperature wereconfirmed. The presence of recycled asphalt pavement (RAP) in a mix tended todecrease the creep compliance (increase the stiffness) and increase the tensilestrength compared to similar mixes without RAP.ii
TABLE OF CONTENTSACKNOWLEDGEMENTS .......................................................................................... IIEXECUTIVE SUMMARY ........................................................................................... IITABLE OF CONTENTS........................................ .................................................... IIILIST OF FIGURES ....................................................................................................VLIST OF TABLES.................................................. ...................................................VIIINTRODUCTION ....................................................................................................... 1OBJECTIVES ............................................................................................................ 2TECHNICAL APPROACH ......................................................................................... 3General .................................................................................................................. 3Materials and Target Specimen Properties ............................................................ 3Specimen Fabrication........................................ ..................................................... 4IDT Testing........................................................ ..................................................... 5Equipment...................................................... ..................................................... 5Creep Compliance Testing ................................................................................. 6Procedure................................................... ..................................................... 7Tensile Strength Testing................................ ................................................... 10Procedure................................................... ................................................... 11Data Reduction.................................................. ................................................... 13Creep Compliance ............................................................................................ 13Poisson’s Ratio ................................................................................................. 15Tensile Strength and Tensile Failure Strain... ................................................... 16RESULTS AND DISCUSSION ................................................................................ 17Creep Compliance............................................. ................................................... 17Poisson’s Ratio.................................................. ................................................... 28iii
Page 1 and 2: • • • • • • • • •
Page 3: TECHNICAL REPORT DOCUMENTATION PAGE
Page 7 and 8: LIST OF FIGURESFigure 1: Test Equip
Page 9 and 10: LIST OF TABLESTable 1: HMA Mixes an
Page 11 and 12: OBJECTIVESThe objective of this pro
Page 13 and 14: voids generally describes the avera
Page 15 and 16: Figure 1: Test Equipment SetupCreep
Page 17 and 18: and level of % air voids. Although
Page 19 and 20: specimen is actually at the test te
Page 21 and 22: same four mixes but at 4.4°C (40°
Page 23 and 24: n Dn PNormalization Constant = ×
Page 25 and 26: where:0.05 ≤ ν ≤ 0.50Tensile S
Page 27 and 28: Table 4: Creep Compliance: 06-101 (
Page 29 and 30: 0.10Creep Compliance (1/GPa)07-123
Page 31 and 32: as it pertains to creep compliance,
Page 33 and 34: However, published documentation of
Page 35 and 36: Getting back to the issue of the er
Page 37 and 38: 0.090Creep Compliance @ 100 sec. @
Page 39 and 40: Table 12: Instrumented Tensile Stre
Page 41 and 42: Table 15: All Tensile Strength: -10
Page 43 and 44: 100090080006-101Virgin binder = PG7
Page 45 and 46: Tensile Failure StrainThe tensile f
Page 47 and 48: Table 18: Tensile Failure Strain: -
Page 49 and 50: CONCLUSIONSExpected trends such as
Page 51 and 52: REFERENCES1. Guide for Mechanistic-
Page 53 and 54: APPENDIX A: CREEP COMPLIANCE
Page 55 and 56:
0.080.070.06Creep Compliance (1/GPa
Page 57 and 58:
0.200.180.160.14Creep Compliance (1
Page 59 and 60:
Page 61 and 62:
Page 63 and 64:
0.300.25Creep Compliance (1/GPa)0.2
Page 65 and 66:
0.140.12Creep Compliance (1/GPa)0.1
Page 67 and 68:
Table B-19: Non-instrumented Data @
Page 69 and 70:
Table B-21: Instrumented Data @ 21.
Page 71 and 72:
Table B-23: Instrumented Data @ 4.4
Page 73 and 74:
Table B-25: Instrumented Data @ -10
Page 75 and 76:
Page 77 and 78:
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Determination of Creep Compliance and Tensile Strength of Hot-Mix ...

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