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88 Introduction This appendix documents the material properties and performance evolution for the new projects (i.e., MT I-15, TN SR 125, IA US 34, and LA US 61 projects) based on (1) the testing of the first-round and second-round field cores and (2) the second-round distress survey results. The first-round field coring took place shortly after construction and the cores were regarded as plant-mixed plant-compacted (PMPC) specimens. The second-round field cores were obtained after about 2 to 3 years in service. Table F.1 presents the schedule of coring for each project. The following material properties and field performance of the new projects are summarized and compared as follows: ⢠Mixture properties: air void content, dynamic modulus values, creep compliance values, fracture properties at the intermediate and low temperatures, and rutting resistance ⢠Binder properties based on the extracted binders: perfor- mance grades (PGs), multiple stress creep recovery (MSCR) values, and fracture properties at the intermediate and low temperatures ⢠Field performance: transverse cracking length, longitudi- nal cracking length, and rutting depth Air Void Contents Table F.2 compares the overall change in air void content of the field cores between the first and second rounds of coring. Except for the MT I-15 project, most of the pavement sec- tions do not show a consistent trend in air void change, and the air void contents in general were maintained at a similar level. For the MT I-15 project, the air void content signifi- cantly decreased for the second round (2013) compared with the first round (2011), which could be related to the heavy traffic (trucks accounted for 26.3% traffic) that this project experienced. Air void content plays a significant role in the evolution of material properties, which is discussed in the fol- lowing sections. One should note that the air void contents presented in Table F.2 are averages based on all the available field cores; therefore, they may not exactly match the sample air void contents of specific mixture tests. Dynamic Modulus Figures F.1 through F.4 present the dynamic modulus master curve comparisons between the first-round and second- round field cores for the MT I-15, TN SR 125, IA US 34, and LA US 61 projects, respectively. For the MT I-15 project (Figure F.1), the dynamic modulus values of the second-round (2013) field cores are statistically higher than those of the first-round (2011) field cores for each technology. However, it is believed that such an increase in the dynamic modulus values should be attributed mainly to the densification effect (reduction of air voids) rather than to the stiffness hardening effect due to aging. In this project, chip seals were applied 1 year after construction, which may have reduced the degree of aging. Binder property changes in this project (as indicated in a later section of this appendix) confirm the limited effect of binder hardening. For the TN SR 125 project (Figure F.2), the second-round (2014) field cores for both the HMA and Evotherm pavements show higher dynamic modulus values than the first-round (2011) field cores, and air void contents did not change sig- nificantly. Aging is believed to have an important effect on the changes in the mechanical properties, particularly with a thin overlay (1.25 inches). For the IA US 34 project (Figure F.3), the second-round (2014) field cores for both the HMA and WMA (Sasobit and Evotherm) pavements show a larger increase in dynamic modulus values than the first-round (2011) field cores. During 3 years of service, the air void contents of the HMA pavement decreased while the air void contents of the Sasobit and Evotherm pavements stayed at the same level. Therefore, A P P E N D I X F Material Properties and Performance Evolution for New Projects
89 Creep Compliance Figures F.5 through F.8 present the creep compliance master curve comparisons between the first-round and second- round field cores for the MT I-15, TN SR 125, IA US 34, and LA US 61 projects, respectively. For the MT I-15 project (Figure F.5), the creep compliance mastercurves for the 2011 and 2013 field cores cross or overlap each other. The slopes of the creep compliance mastercurves, which are inputs to the AASHTOWare Pavement ME Design thermal cracking model, are lower for the 2013 field cores than for the 2011 field cores, indicating that the capability for stress relaxation (or resistance to thermal cracking) could be less for the 2013 field cores than for the 2011 field cores in terms of particular mix type. Project First-Round Coring Year Second-Round Coring Year MT I-15 2011 2013 TN SR 125 2011 2014 IA US 34 2011 2014 LA US 61 2013 2015 Table F.1. Schedule of coring for each project. Project Mix Type First-Round Air Void Content, % Second-Round Air Void Content, % MT I-15 HMA 6.6 (0.6) 2.4 (0.8) Sasobit 4.9 (0.6) 3.0 (0.5) Evotherm 4.3 (0.9) 2.2 (0.5) Foaming 5.3 (0.9) 2.4 (0.8) TN SR 125 HMA 5.6 (0.8) 5.6 (0.8) Evotherm 7.2 (1.3) 8.0 (1.2) IA US 34 HMA 7.2 (1.4) 4.6 (2.4) Sasobit 8.8 (1.4) 10.8 (1.0) Evotherm 9.0 (0.5) 8.2 (1.2) LA US 61 HMA 4.6 (0.6) 4.6 (0.5) Sasobit 5.9 (0.8) 6.2 (0.7) Evotherm 7.8 (0.8) 6.1 (0.5) Note: The numbers in parentheses indicate the standard deviation. Table F.2. Comparisons of overall air void contents between first-round and second-round field cores. Note: The percentage in parentheses indicates the air void content of the specimen. 100 1000 10000 100000 0.0001 0.1 100 100000 100000000 D yn am ic M od ul us (M Pa ) Reduced Frequency (Hz) 2011 HMA#3 (4.1%) 2011 HMA#7 (4.7%) 2011 HMA#12 (6.7%) 2011 Sasobit#3 (5.3%) 2011 Sasobit#8 (3.2%) 2011 Sasobit#15 (4.6%) 2011 Evo#3 (2.3%) 2011 Evo#9 (4.4%) 2011 Evo#12 (3.5%) 2011 Foam#1 (2.8%) 2011 Foam#2 (2.5%) 2011 Foam#6 (3.6%) 2013 HMA F1 (3.6%) 2013 HMA M5 (2.2%) 2013 HMA T3 (2.2%) 2013 Sas F1 (3.4%) 2013 Sas M3 (3.4%) 2013 Sas T2 (2.5%) 2013 Evo M1 (2.1%) 2013 Evo M5 (2.3%) 2013 Evo T1 (2.3%) 2013 Foam F2 (2.1%) Figure F.1. Comparisons of dynamic modulus mastercurves at the 68çF reference temperature between 2011 and 2013 field cores (MT I-15 project). this increase in dynamic modulus value is presumably due to the significant field aging of the asphalt binder. For the LA US 61 project (Figure F.4), the second-round (2015) field cores for both the HMA and WMA (Sasobit and Evotherm) pavements show a slight increase in dynamic modulus values compared with the first-round (2013) field cores, which is likely due to aging.
90 100 1000 10000 100000 0.0001 0.1 100 100000 100000000 1E+11 D yn am ic M od ul us (M Pa ) Reduced Frequency (Hz) 2011 HMA #3 (5.7%) 2011 HMA #5 (6.0%) 2011 HMA #17 (6.6%) 2011 Evotherm #5 (6.2%) 2011 Evotherm #8 (8.3%) 2011 Evotherm #18 (9.0%) 2014 HMA F3 (6.4%) 2014 HMA M3 (6.3%) 2014 HMA T1 (7.0%) 2014 Evotherm F3 (9.3%) 2014 Evotherm M2 (8.6%) 2014 Evotherm T3 (7.5%) Figure F.2. Comparisons of dynamic modulus mastercurves at the 68çF reference temperature between 2011 and 2014 field cores (TN SR 125 project). 10 100 1000 10000 100000 0.0001 0.1 100 100000 100000000 1E+11 D yn am ic M od ul us (M Pa ) Reduced Frequency (Hz) 2011 HMA #4 (6.7%) 2011 HMA #5 (7.2%) 2011 HMA #6 (7.4%) 2011 Sas #4 (6.4%) 2011 Sas #5 (7.2%) 2011 Sas #6 (9.1%) 2011 Evo #5 (8.6%) 2011 Evo #8 (8.4%) 2011 Evo #1 (8.0%) 2014 HMA F3 (1.7%) 2014 HMA M3 (6.4%) 2014 HMA T3 (1.2%) 2014 Sas F3 (11.1%) 2014 Sas M2 (10.4%) 2014 Sas T1 (8.9%) 2014 Evo F1 (7.5%) 2014 Evo M5 (9.2%) 2014 Evo T1 (7.5%) Figure F.3. Comparisons of dynamic modulus mastercurves at the 68çF reference temperature between 2011 and 2014 field cores (IA US 34 project).
91 100 1000 10000 100000 0.0001 0.1 100 100000 100000000 D yn am ic M od ul us (M Pa ) Reduced Frequency (Hz) 2013 HMA L1 (4.9%) 2013 HMA L2 (5.0%) 2013 HMA L3 (4.0%) 2013 Sas A1 (5.0%) 2013 Sas A3 (6.3%) 2013 Sas L4 (6.8%) 2013 Evo A2 (8.6%) 2013 Evo D2 (6.7%) 2013 Evo E2 (7.1%) 2015 HMA M2 (4.2%) 2015 HMA T1 (4.9%) 2015 HMA T2 (4.5%) 2015 Sas F3 (5.5%) 2015 Sas M4 (6.0%) 2015 Sas T3 (7.3%) 2015 Evo M5 (5.5%) 2015 Evo M6 (6.3%) Figure F.4. Comparisons of dynamic modulus mastercurves at the 68çF reference temperature between 2013 and 2015 field cores (LA US 61 project). 1E-11 1E-10 1E-09 1E-08 0.0000001 1E-11 1E-08 0.00001 0.01 10 10000 C re ep co m pl ia nc e ( 1/P a) Reduced Time (s) 2011 HMA#3 (4.1%) 2011 HMA#7 (4.7%) 2011 HMA#12 (6.7%) 2011 Sas#3 (5.3%) 2011 Sas#8 (3.2%) 2011 Sas#15 (4.6%) 2011 Evo#3 (3.5%) 2011 Evo#9 (2.3%) 2011 Evo#12 (4.4%) 2011 Foam#1 (2.8%) 2011 Foam #2 (2.5%) 2011 Foam#6 (3.6%) 2013 HMA F1 (3.6%) 2013 HMA M5 (2.2%) 2013 HMA T3 (2.2%) 2013 Sas F1 (3.4%) 2013 Sas M3 (3.4%) 2013 Sas T2 (2.5%) 2013 Evo M1 (2.1%) 2013 Evo M5 (2.3%) 2013 Evo T1 (2.3%) 2013 Foam F2 (2.1%) 2013 Foam M2 (3.0%) 2013 Foam T1 (2.4%) Figure F.5. Comparisons of creep compliance mastercurves at the 68çF reference temperature between 2011 and 2013 field cores (MT I-15 project).
92 1E-11 1E-10 1E-09 1E-08 0.0000001 1E-10 0.0000001 0.0001 0.1 100 100000 100000000 C re ep co m pl ia nc e ( 1/P a) Time (s) 2011 HMA #4 (6.7%) 2011 HMA #5 (7.2%) 2011 HMA #6 (7.4%) 2011 Sas #4 (6.4%) 2011 Sas #5 (7.2%) 2011 Sas #6 (9.1%) 2011 Evo #5 (8.6%) 2011 Evo #8 (8.4%) 2011 Evo #1 (8.0%) 2014 HMA F3 (1.7%) 2014 HMA M3 (6.4%) 2014 HMA T3 (1.2%) 2014 Sas F3 (11.1%) 2014 Sas M2 (10.4%) 2014 Sas T1 (8.9%) 2014 Evo F1 (7.5%) 2014 Evo M5 (9.2%) Figure F.7. Comparisons of creep compliance mastercurves at the 68çF reference temperature between 2011 and 2014 field cores (IA US 34 project). 1E-11 1E-10 1E-09 1E-08 0.0000001 1E-12 1E-09 0.000001 0.001 1 1000 1000000 C re ep co m pl ia nc e ( 1/P a) Reduced Time (s) 2011 HMA #3 (5.7%) 2011 HMA #5 (6.0%) 2011 HMA #17 (6.6%) 2011 Evotherm #8 (8.3%) 2011 Evotherm #8 (8.3%) 2011 Evotherm #18 (9.0%) 2014 HMA F3 (6.4%) 2014 HMA M3 (6.3%) 2014 HMA T1 (7.0%) 2014 Evotherm F3 (9.3%) 2014 Evotherm M2 (8.6%) 2014 Evotherm T3 (7.5%) Figure F.6. Comparisons of creep compliance mastercurves at the 68çF reference temperature between 2011 and 2014 field cores (TN SR 125 project).
93 For the TN SR 125 project (Figure F.6), the creep compli- ance curves of the 2014 field cores are lower than those of the 2011 field cores for both the HMA and the Evotherm mix- tures. Also, the shape of the creep compliance mastercurves of the 2014 field cores are flatter (have a lower slope) than those of the 2011 field cores, indicating that the stress relaxation ability has decreased and the thermal cracking resistance has been compromised, as expected. For the IA US 34 project (Figure F.7), the creep compliance mastercurves of the 2014 field cores are lower than those of the 2011 field cores for both the HMA and WMA mixtures. Also, the slopes of the creep compliance mastercurves for the 2014 field cores are comparable to those of the 2011 field cores, indicating that the stress relaxation capability decreased slightly over time. For the LA US 61 project (Figure F.8), the creep compli- ance mastercurves of the 2015 field cores are lower (indicat- ing more stiffness) than those of the 2013 field cores for both the HMA and the WMA mixtures, which may be attributable to the effects of aging. Mixture IDT Fracture Properties at the Intermediate Temperature Table F.3 presents comparisons between the second-round and first-round field cores in terms of fracture work density. As shown, no consistent change trend is evident for fracture work density. The fracture work density values of the second- round field cores are statistically higher than those of the first-round field cores for the MT I-15 project. For the other 1E-11 1E-10 1E-09 1E-08 0.0000001 1E-14 1E-11 1E-08 0.00001 0.01 10 10000 C re ep co m pl ia nc e ( 1/P a) Reduced Time (s) 2013 HMA L1 (4.9%) 2013 HMA L2 (5.0%) 2013 HMA L3 (4.0%) 2013 Sas A1 (5.0%) 2013 Sas A3 (6.3%) 2013 Sas L4 (6.8%) 2013 Evo A2 (8.6%) 2013 Evo D2 (6.7%) 2013 Evo E2 (7.1%) 2015 HMA M2 (4.2%) 2015 HMA T1 (4.9%) 2015 HMA T2 (4.5%) 2015 Sas F3 (5.5%) 2015 Sas M4 (6.0%) 2015 Sas T3 (7.3%) 2015 Evo M5 (5.5%) 2015 Evo M6 (6.3%) Figure F.8. Comparisons of creep compliance mastercurves at the 68çF reference temperature between 2013 and 2015 field cores (LA US 61 project). Project Mix Type First-Round Fracture Work Density, kPa Second-Round Fracture Work Density, kPa First-Round Air Void Content, % Second-Round Air Void Content, % MT I-15 HMA 88.4 (5.5) 158.9 (9.6) 5.2 2.7 Sasobit 97.5 (6.6) 143.8 (7.5) 4.4 3.1 Evotherm 90.9 (8.5) 160.7 (17.6) 3.4 2.2 Foaming 87.1 (4.9) 163.7 (15.1) 3.0 2.5 TN SR 125 HMA 116.1 (14.4) 100.2 (4.9) 7.5 5.9 Evotherm 85.6 (6.3) 75.0 (4.1) 7.2 8.0 IA US 34 HMA 95.1 (11.6) 92.9 (12.5) 7.1 3.2 Sasobit 84.8 (19.2) 78.2 (12.1) 7.6 10.2 Evotherm 92.9 (8.5) 98.1 (7.9) 8.3 8.1 LA US 61 HMA 139.1 (27.0) 109.3 (9.9) 4.6 4.5 Sasobit 148.8 (18.6) 89.3 (4.4) 6.0 6.3 Evotherm 141.3 (14.7) 109.8 (8.3) 7.5 5.8 Note: The numbers in parentheses indicate the standard deviation. Table F.3. Comparisons of fracture work density (at 68çF) between first-round and second-round field cores.
94 projects, the fracture work density values of the second-round field cores are either comparable with (IA US 34) or lower (TN SR 125 and LA US 61) than those of the first-round field cores. The higher fracture work density values indicate more resistance to bottom-up fatigue cracking, whereas the lower fracture work density values indicate less resistance to bottom-up fatigue cracking (Wen 2012). Table F.4 presents comparisons between the second-round and first-round field cores in terms of IDT strength. For both the HMA and the WMA pavements, the IDT strength values of the second-round field cores are either comparable with (LA US 61, Sasobit and Evotherm) or higher (MT I -15, TN SR 125, and IA US 34) than those of the first-round field cores, indicating reduced cracking potential based on the analysis results from this study. The HMA pavement for the LA US 61 project is the only one that shows lower IDT strength values for the second-round field cores than for the first-round field cores. Table F.5 presents comparisons between the second- round and first-round field cores in terms of vertical failure deformation. For both the HMA and the WMA pavements, the vertical failure deformation values of the second-round field cores are either comparable with (MT I-15) or lower (TN SR 125, IA US 34, and LA US 61) than those of the first-round field cores. The lower vertical failure deformation values indicate a decreased resistance to top-down cracking. Table F.6 presents comparisons between the second-round and first-round field cores in terms of horizontal failure strain. For both the HMA and the WMA pavements, the hor- izontal failure strain values of the second-round field cores are either comparable with (MT I-15 and LA US 61) or lower (TN SR 125 and IA US 34) than those of the first-round field cores. The lower horizontal failure strain values indicate that the top-down fatigue resistance of the asphalt mixtures deteriorated rapidly during 3 years of service. It should be noted that for the MT I-15 project, the air void contents of the 2013 field cores were much lower than those of the 2011 field cores. Figures F.9 (a) through (d) present the correlations between the IDT fracture parameters tested at 68°F and the air void contents. Also, for the LA US 61 project, Project Mix Type First-Round Vertical Failure Deformation, mm Second-Round Vertical Failure Deformation, mm First-Round Air Void Content, % Second-Round Air Void Content, % MT I-15 HMA 1.7 (0.1) 1.8 (0.3) 5.2 2.7 Sasobit 1.8 (0.1) 1.8 (0.2) 4.4 3.1 Evotherm 1.8 (0.2) 1.9 (0.1) 3.4 2.2 Foaming 1.8 (0.1) 1.9 (0.1) 3.0 2.5 TN SR 125 HMA 2.3 (0.3) 1.6 (0.3) 7.5 5.9 Evotherm 2.0 (0.2) 1.3 (0.03) 7.2 8.0 IA US 34 HMA 2.4 (0.4) 1.4 (0.1) 7.1 3.2 Sasobit 1.8 (0.2) 1.4 (0.1) 7.6 10.2 Evotherm 2.0 (0.2) 1.5 (0.1) 8.3 8.1 LA US 61 HMA 1.8 (0.1) 1.2 (0.05) 4.6 4.5 Sasobit 1.9 (0.1) 1.5 (0.1) 6.0 6.3 Evotherm 1.8 (0.1) 1.2 (0.1) 7.5 5.8 Note: The numbers in parentheses indicate the standard deviation. Table F.5. Comparisons of vertical failure deformation (at 68çF) between first-round and second-round field cores. Project Mix Type First-Round IDT Strength, kPa Second-Round IDT Strength, kPa First-Round Air Void Content, % Second-Round Air Void Content, % MT I-15 HMA 1458.1 (182.3) 2648.7 (133.6) 5.2 2.7 Sasobit 1685.4 (91.7) 2772.9 (495.6) 4.4 3.1 Evotherm 1466.2 (74.7) 2647.1 (184.6) 3.4 2.2 Foaming 1472.0 (97.2) 2737.4 (118.6) 3.0 2.5 TN SR 125 HMA 1328.6 (213.9) 2405.7 (60.1) 7.5 5.9 Evotherm 1221.3 (153.2) 2292.1 (253.1) 7.2 8.0 IA US 34 HMA 1415.1 (76.6) 2787.1 (206.7) 7.1 3.2 Sasobit 1261.6 (200.7) 2016.6 (301.2) 7.6 10.2 Evotherm 1305.6 (168.5) 2540.8 (299.0) 8.3 8.1 LA US 61 HMA 3771.7 (222.3) 2877.6 (223.3) 4.6 4.5 Sasobit 3425.1 (129.4) 3711.7 (397.5) 6.0 6.3 Evotherm 3041.5 (279.6) 2874.2 (368.1) 7.5 5.8 Note: The numbers in parentheses indicate the standard deviation. Table F.4. Comparisons of IDT strength (at 68çF) between first-round and second-round field cores.
95 Project Mix Type First-Round HFS, mm/mm Second-Round HFS, mm/mm First-Round Air Void Content, % Second-Round Air Void Content, % MT I-15 HMA 0.0096 (0.0015) 0.008 (0.0013) 5.2 2.7 Sasobit 0.008 (0.0002) 0.0078 (0.0011) 4.4 3.1 Evotherm 0.0122 (0.0017) 0.0104 (0.0013) 3.4 2.2 Foaming 0.0119 (0.0006) 0.0101 (0.0006) 3.0 2.5 TN SR 125 HMA 0.0201 (0.0044) 0.0035 (0.0007) 7.5 5.9 Evotherm 0.0099 (0.0022) 0.0019 (0.0016) 7.2 8.0 IA US 34 HMA 0.0168 (0.0058) 0.0028 (0.001) 7.1 3.2 Sasobit 0.0156 (0.0113) 0.0047 (0.0008) 7.6 10.2 Evotherm 0.01 (0.0011) 0.004 (0.0003) 8.3 8.1 LA US 61 HMA 0.0033 (0.0007) 0.004 (0.0007) 4.6 4.5 Sasobit 0.004 (0.0007) 0.0036 (0.001) 6.0 6.3 Evotherm 0.0051(0.0066) 0.0042 (0.0002) 7.5 5.8 Notes: The numbers in parentheses indicate the standard deviation. HFS: horizontal failure strain. Table F.6. Comparisons of horizontal failure strain (at 68çF) (HFS) between first-round and second-round field cores. (a) Fracture work density y = 298.41x 0.791 R² = 0.5686 0 50 100 150 200 0.0 2.0 4.0 6.0 D en si ty of Fr ac tu re W or k, kP a Air Void, % (b) IDT Strength y = 5036.1x 0.786 R² = 0.5025 0 500 1000 1500 2000 2500 3000 0.0 2.0 4.0 6.0 ID T St re ng th ,k Pa Air Void, % (c) Vertical Failure Deformation y = 2.0904x 0.12 R² = 0.8187 1.5 1.6 1.7 1.8 1.9 2.0 0.0 2.0 4.0 6.0 V er ti ca lf ai lu re de fo rm ati on ,m m Air Void, % (d) Horizontal Failure Strain y = 0.0109x 0.108 R² = 0.0291 0.000 0.004 0.008 0.012 0.016 0.0 2.0 4.0 6.0H or iz on ta lf ai lu re st ra in , m m /m m Air Void, % Figure F.9. Relationship between IDT fracture parameters (at 68çF) and air void content: (a) fracture work density, (b) IDT strength, (c) vertical failure deformation, and (d) horizontal failure strain (MT I-15 project).
96 Project Mix Type First-Round Fracture Work Density, kPa Second-Round Fracture Work Density, kPa First-Round Air Void Content, % Second-Round Air Void Content, % MT I-15 HMA 28.7 (12.7) 65.8 (5.7) 6.1 2.7 Sasobit 32.4 (4.1) 93.2 (9.9) 4.1 3.0 Evotherm 55.7 (28.4) 121.1 (17.2) 3.5 2.7 Foaming 60.1 (15.6) 99.9 (10.1) 2.0 2.4 TN SR 125 HMA 84.9 (18.3) 52.7 (6.9) 6.0 5.9 Evotherm 119.8 (58.5) 38.3 (2.9) 7.0 7.8 IA US 34 HMA 55.6 (3.0) 52.6 (11.0) 6.1 5.3 Sasobit 44.9 (11.2) 45.7 (2.1) 8.2 11.4 Evotherm 32.0 (11.2) 37.9 (3.5) 9.0 7.6 LA US 61 HMA NA 74.1 (10.4) NA 4.6 Sasobit 50.7 (5.0) 79.7 (4.9) 5.7 6.0 Evotherm 56.6 (7.5) 50.9 (7.6) 8.1 5.8 Note: The test data for the HMA for the second-round field cores were not available for the low temperature IDT test. Table F.7. Comparisons of fracture work density (at 14çF) between the first-round and second-round field cores Figure F.10. Contaminated field core for LA US 61 project. pavement in the LA US 61 project due to a lack of 2013 test data. The fracture work density values did not change signi- ficantly for any of the mixtures in the IA US 34 project, which is consistent with the findings regarding the slopes of the mastercurves for creep compliance. The higher frac- ture work density values indicate more resistance to trans- verse cracking (i.e., thermal cracking), whereas the lower fracture work density values indicate less resistance to trans- verse cracking. Table F.8 presents comparisons between the first-round and second-round field cores in terms of IDT strength at the low temperature (14°F). For both the HMA and the WMA pavements, the IDT strength values of the second-round field cores are either equal to the first-round cores or significantly higher than the first-round cores. In particular, MT I-15 Foam- ing cores and LA US 61 Evotherm cores showed statistically equal IDT strength in the second-round as compared with the first-round results; all other projects showed statistically higher IDT strength in the second round. No comparisons were made for the HMA pavements of the LA US 61 project due to a lack of 2013 test data. As mentioned earlier, for the MT I-15 project, the statisti- cally higher fracture work density and IDT strength values of the 2013 field cores compared with those of the 2011 field cores are due to the lower air void contents of the 2013 field cores, as shown in Figure F.11, instead of due to aging. This will be addressed in the binder section. Hamburg Wheel-Tracking Test Results Table F.9 shows the rutting resistance index (RRI) compar- isons between the second-round field cores and first-round field cores/PMLC specimens for the MT I-15, TN SR 125, IA US 34, and LA US 61 projects. For the MT I-15 project, the field cores extracted in 2015 had been contaminated with dirt, as shown in Figure F.10. Mixture IDT Fracture Properties at the Low Temperature Table F.7 presents comparisons between the first-round and second-round field cores in terms of fracture work density at the low temperature (14°F). No consistent trend is evident for changes in fracture work density. The fracture work density values for the second-round field cores are higher than those for the first-round field cores for the MT I-15 project and for the Sasobit from the LA US 61 project. For the other projects, the fracture work density values of the second-round field cores are either equal to (IA US 34 and LA US 61 Evotherm) or significantly lower (TN SR 125) than those of the first- round field cores. No comparison was made for the HMA
97 Project Mix Type First-Round IDT Strength, kPa Second-Round IDT Strength, kPa First-Round Air Void Content, % Second-Round Air Void Content, % MT I-15 HMA 3360.4 (1437.4) 4733.6 (359.4) 6.1 2.7 Sasobit 4218.4 (504.8) 5227.0 (697.4) 4.1 3.0 Evotherm 4728.5 (470.0) 5567.4 (503.0) 3.5 2.7 Foaming 5599.3 (194.3) 5441.1 (375.5) 2.0 2.4 TN SR 125 HMA 2998.1 (52.5) 3152.7 (197.8) 6.0 5.9 Evotherm 2002.7 (412.4) 3122.0 (232.8) 7.0 7.8 IA US 34 HMA 3222.1 (287.3) 3626.3 (155.4) 6.1 5.3 Sasobit 2757.6 (465.2) 2895.5 (414.1) 8.2 11.4 Evotherm 2221.6 (434.0) 2984.9 (166.6) 9.0 7.6 LA US 61 HMA NA 4843.1 (293.9) NA 4.6 Sasobit 3478.7 (898.9) 5215.1 (102.5) 5.7 6.0 Evotherm 4058.2 (423.6) 4024.0 (612.4) 8.1 5.8 Note: The numbers in parentheses indicate the standard deviation. Table F.8. Comparisons of IDT strength (at 14çF) between the first-round and second-round field cores. Project Mix Type First-Round RRI Value Second-Round RRI Value First-Round Air Void Content, % Second-Round Air Void Content, % MT I-15 HMA 17323 (379) 12830 (4814) 5.7 2.5 Sasobit 17874 (8) 16668 (811) 5.9 3.1 Evotherm 16535 (323) 16570 (1731) 6.0 2.7 Foaming 17244 (150) 10500 (6646) 6.0 2.7 TN SR 125 HMA 15796 (-) 17020 (75) NA 6.5 Evotherm 9765 (-) 17339 (572) NA 7.9 IA US 34 HMA 3585 (467) 7095 (6677) 7.3 6.0 Sasobit 1428 (16) 2419 (856) 8.5 7.3 Evotherm 2981 (1153) 3590 (1188) 9.0 6.6 LA US 61* HMA 16850 (-) 18310 (482) 7.0 4.9 Sasobit 17559 (-) 18745 (403) 7.0 5.7 Evotherm 17008 (-) 18480 (104) 7.0 6.7 Note: The numbers in parentheses indicate the standard deviation. * For LA US 61 project, the PMLC specimens were used for the Hamburg test. Table F.9. Comparisons of RRI between the first-round and second-round field cores. (a) Fracture Work Density y = 178.29e 0.316x R² = 0.6078 0 40 80 120 160 0.0 5.0 10.0D en si ty o f F ra ct ur e W or k, kP a Air void, % (b) IDT Strength y = 8344.4x 0.483 R² = 0.8911 0 2000 4000 6000 8000 0.0 5.0 10.0 ID T St re ng th , k Pa Air void, % Figure F.11. Relationship between IDT fracture parameters (at 14çF) and air void content: (a) fracture work density and (b) IDT strength (MT I-15 project).
98 the 2013 field cores show comparable RRI values with the 2011 field cores, although the 2013 field cores have lower air void contents due to traffic densification. The laydown of the chip seal may have slowed the aging of the pavement and thus led to unimproved rutting resistance. It should be noted that very high rut depth variations were found in the 2013 HMA and Foaming Hamburg wheel tracking (HWT) test results although the air void contents of those samples were similar. The reason for this finding is not known. For the TN SR 125 project, the rutting resistance of the 2014 field cores improved compared with the 2011 field cores, mainly due to the aging effect that can be seen in the extracted binder PG test results. For the IA US 34 project, a general trend is evident that the rutting resistance of the 2014 field cores is slightly greater than for the 2011 field cores. For the LA US 61 project, RRI comparisons were made between the 2015 field cores and 2013 plant-mixed laboratory- compacted (PMLC) specimens. The 2015 field cores have higher RRI values than the 2013 PMLC specimens, which should be related to the effect of aging and change in air void content. Field cores were not obtained in 2013. Extracted Binder Performance Grades Table F.10 presents the high and low temperature PG com- parisons between the first-round extracted binders and the second-round extracted binders. All binders were recovered from field cores. For the MT I-15 project, the PGs of the extracted binders in 2013 are close to those in 2011. The chip seals that covered the surfaces could have reduced the asphalt aging. For the TN SR 125, IA US 34, and LA US 61 projects, both the high and low temperature PGs of the second-round extracted binders are higher than those of the first-round extracted binders, which clearly indicates the effect of field aging during 3 years of service. Extracted Binder Multiple Stress Creep Recovery Test Results Table F.11 presents the nonrecoverable creep compliance (Jnr3.2) and percentage of recovery (R3.2) comparisons between the first-round and second-round extracted binders. For the MT I-15 project, the trends of Jnr3.2 and R3.2 are not consistent among the HMA and the different WMA technologies, which again could be attributed to the reduced aging effect due to the chip seal surface treatment. For the TN SR 125, IA US 34, and LA US 61 projects, both the HMA and the WMA binders extracted in the second round show statistically lower Jnr3.2 and higher R3.2 values than those extracted in the first round, which indicates that the rutting resistance of the pavements improved over time. Extracted Binder Fracture Properties at the Intermediate Temperature Tables F.12 and F.13 present the maximum stress and frac- ture energy comparisons (at 68°F) between the first-round and second-round extracted binders, respectively. Generally, the binders extracted from the second-round field cores show statistically higher maximum stress values (less resistance to top-down fatigue cracking) and fracture energy values (less resistance to bottom-up fatigue cracking) than those extracted from the first-round field cores, except that the Foaming binder extracted in 2013 from the MT I-15 project shows statistically less maximum stress and fracture energy than that extracted in 2011. It is noted that the PGs of the 2013 binders are not significantly different from the PGs of the 2011 recovered binders. This phenomenon warrants further study. It was also observed that the 2014 extracted Project Binder Type First-Round PG, % Second-Round PG, % MT I-15 HMA 70.9-26.0 (0.0-0.8) 69.2-24.6 (0.4-0.3) Sasobit 71.7-27.1 (0.1-0.1) 69.3-26.6 (0.4-0.2) Evotherm 70.2-27.4 (0.3-0.9) 68.6-27.6 (0.6-0.1) Foaming 69.0-24.5 (0.3-0.7) 70.2-25.8 (0.6-1.1) TN SR 125 HMA 78.7-21.1 (0.4-0.4) 85.8-11.8 (0.5-0.2) Evotherm 66.2-20.5 (0.5-0.0) 87.5-8.7 (0.6-0.2) IA US 34 HMA 65.7-25.5 (0.3-0.7) 74.1-23.3 (0.3-0.1) Sasobit 66.5-27.1 (0.2-0.0) 72.4-23.6 (0.3-0.03) Evotherm 66.2-26.2 (0.5-0.4) 72.9-23.6 (0.2-0.1) LA US 61 HMA 81.8-16.7 (0.3-0.5) 86.0-14.8 (0.5-0.4) Sasobit 81.5-19.6 (0.6-0.4) 86.8-14.7 (1.2-1.5) Evotherm 80.7-18.8 (0.2-0.8) 86.9-15.8 (0.3-0.5) Note: The numbers in parentheses indicate the standard deviation. Table F.10. Comparisons of performance grades between the first-round and second-round extracted binders.
99 Project Binder Type Jnr3.2 R3.2 First-Round, kPa Second-Round, kPa First-Round, % Second-Round, % MT I-15 HMA 0.38 (0.04) 0.32 (0.01) 49.3 (1.1) 38.8 (0.2) Sasobit 0.37 (0.00) 0.21 (0.00) 50.2 (0.5) 55.0 (0.1) Evotherm 0.18 (0.01) 0.20 (0.01) 64.3 (0.3) 64.2 (0.3) Foaming 0.15 (0.00) 0.20 (0.00) 72.2 (0.2) 64.1 (0.5) TN SR 125 HMA 0.45 (0.02) 0.11 (0.01) 29.4 (1.2) 49.1 (0.2) Evotherm 0.76 (0.05) 0.08 (0.01) 27.6 (0.5) 52.2 (0.3) IA US 34 HMA 1.17 (0.26) 0.36 (0.02) 6.0 (1.2) 15.9 (0.4) Sasobit 1.57 (0.10) 0.50 (0.03) 3.2 (0.04) 13.6 (0.2) Evotherm 1.35 (0.1) 0.45 (0.01) 4.6 (0.7) 13.1 (0.1) LA US 61 HMA 0.67 (0.02) 0.31 (0.01) 33.5 (0.7) 50.1 (0.3) Sasobit 0.68 (0.02) 0.32 (0.00) 34.7 (0.8) 47.2 (0.3) Evotherm 0.59 (0.03) 0.28 (0.00) 37.3 (1.4) 49.0 (0.1) Note: The numbers in parentheses indicate the standard deviation. Table F.11. Comparisons of MSCR Jnr3.2 and R3.2 values between the first-round and second-round extracted binders. Project Binder Type First-Round Maximum Stress, kPa Second-Round Maximum Stress, kPa MT I-15 HMA 367.6 (7.8) 438.2 (7.2) Sasobit 463.5 (15.3) 495.4 (15.1) Evotherm 372.6 (17.6) 413.8 (11.6) Foaming 503.4 (7.7) 443.2 (3.7) TN SR 125 HMA 905.9 (84.1) 2085.6 (74.3) Evotherm 614.3 (12.8) 2519.2 (110.7) IA US 34 HMA 415.4 (12.2) 1457.6 (265.9) Sasobit 339.7 (19.9) 1193.5 (28.5) Evotherm 428.4 (4.1) 1386.3 (107.0) LA US 61 HMA 1315.3 (1.1) 2455.6 (134.2) Sasobit 1356.3 (6.6) 2693.9 (195.7) Evotherm 1008.1 (11.3) 2618.8 (381.2) Note: The numbers in parentheses indicate the standard deviation. Table F.12. Comparisons of maximum stress (at 68çF) between the first-round and second-round extracted binders. Project Binder Type First-Round Fracture Energy, kPa Second-Round Fracture Energy, kPa MT I-15 HMA 3479.2 (74.9) 4279.8 (175.1) Sasobit 5411.5 (1073.3) 4951.1 (249.2) Evotherm 3639.0 (250.5) 4132.6 (205.2) Foaming 4836.0 (81.3) 4526.5 (24.8) TN SR 125 HMA 1563.6 (189.9) 2437.5 (368.0) Evotherm 3475.7 (615.3) 2560.5 (301.5) IA US 34 HMA 744.3 (14.6) 1851.6 (229.9) Sasobit 645.4 (22.7) 1574.7 (28.7) Evotherm 839.2 (57.8) 1825.3 (138.0) LA US 61 HMA 8599.2 (1.3) 12000.0 (698.4) Sasobit 8335.2 (2.4) 14532.1 (2749.8) Evotherm 8237.3 (13.6) 11635.6 (2912.4) Note: The numbers in parentheses indicate the standard deviation. Table F.13. Comparisons of fracture energy (at 68çF) between the first-round and second-round extracted binders.
100 Evotherm binder from the TN 125 project shows statisti- cally lower fracture energy values than the 2011 Evotherm extracted binder. Extracted Binder Fracture Properties at the Low Temperature Table F.14 presents the binder failure strain (at 41°F) between the first-round and second-round extracted binders. For the MT I-15 project, the failure strain values of the 2013 extracted binders are statistically higher (indicating better resis- tance to thermal cracking) than those of the 2011 extracted binders. Such value changes indicate that fundamental changes may have taken place in these binders, which is worth further study. Chip seals play a positive role in reducing the aging of the existing asphalt layer. However, an extensive study of the effects of chip seals on the asphalt binder in the underlying asphalt layer is beyond the scope of this study. For the TN SR 125 and LA US 61 projects, the failure strain values of the second-round extracted binders are much lower (indicating less resistance to thermal cracking) than those of the first-round extracted binders, which can be explained by the aging resulting from years of service. The lower binder failure strain values indicate a decrease in the resistance to ther- mal cracking. For the IA US 34 project, the failure strain values of the 2014 extracted binders are comparable to those of the 2011 extracted binders. Summary of Material Properties Comparisons between HMA and WMA Pavements Tables F.15 through F.18 present the material properties comparisons between HMA and WMA pavements for the first and second rounds. In most cases, for the MT I-15, IA US 34, and LA US 61 projects, the rankings between HMA and WMA pavements in the first round are largely consistent with those in the second round. For the TN SR 125 project, although most of the rankings between HMA and WMA pavements in 2011 remained the same in 2014, the most pronounced changes are that the dif- ferences in the PGs and fracture energy values of the HMA and the Evotherm WMA binders in 2011 were no longer evi- dent in 2014. Summary of Pavement Performance MT I-15 Project For the MT I-15 project, chip seals were placed on the pave- ment surface after 1 year of service for the purpose of pro- tecting the overlay. During the second-round distress survey (i.e., 2 years after construction), only transverse cracking was found, and no longitudinal cracking or measurable rutting was recorded. Figure F.12 clearly shows transverse cracking on the surface of the chip seal layer. These transverse cracks are in the form of either surface-initiated thermal cracking or reflective cracking, as illustrated by the field cores shown in Figure F.13. Figure F.14 presents comparisons of transverse crack lengths (based on crack width and severity) between HMA and WMA pavements for the transverse cracks measured in the existing pavement before construction and those mea- sured for the 2013 second-round field distress survey. The WMA pavements show transverse crack lengths that are comparable with those of the HMA pavement in the second- round distress survey. Comparing the transverse crack lengths before and after the overlay was constructed, it appears that the existing transverse cracks in all the HMA and WMA pavements, except the Evotherm WMA pavement, reflected to the pavement surface within 2 years of service. Although Project Binder Type First-Round Failure Strain, mm/mm Second-Round Failure Strain, mm/mm MT I-15 HMA 5.2 (1.0) 7.0 (1.1) Sasobit 5.9 (1.0) 9.2 (0.1) Evotherm 6.1 (0.8) 8.9 (0.4) Foaming 6.1 (0.7) 8.2 (0.9) TN SR 125 HMA 1.1 (0.1) 0.3 (0.2) Evotherm 1.2 (0.1) 0.3 (0.1) IA US 34 HMA 1.1 (0.2) 0.9 (0.02) Sasobit 1.2 (0.1) 1.1 (0.2) Evotherm 1.3 (0.3) 0.8 (0.2) LA US 61 HMA 4.5 (0.4) 2.8 (0.04) Sasobit 5.1 (0.8) 2.6 (0.3) Evotherm 6.8 (0.4) 2.7 (0.2) Note: The numbers in parentheses indicate the standard deviation. Table F.14. Comparisons of failure strain (at 41çF) between the first-round and second-round extracted binders.
Material Material Property HMA vs. WMA 2011 2013 14°F 68°F 86°F 14°F 68°F 86°F Mix Dynamic Modulus Sasobit < = = = = = Evotherm < = = = = > Foaming = = = = = = Creep Compliance Sasobit = > > = > = Evotherm = = = = > = Foaming = = < = > = Vertical Failure Deformation (68°F) Sasobit = = Evotherm = = Foaming = = Fracture work density (14°F) Sasobit = < Evotherm = < Foaming < < Rutting Resistance Index Sasobit = = Evotherm = = Foaming = = Binder PG Sasobit = = Evotherm = = Foaming = = MSCR (R3.2) Sasobit = < Evotherm < < Foaming < < Fracture Energy (68°F) Sasobit < < Evotherm = = Foaming < < Failure Strain (41°F) Sasobit = < Evotherm = = Foaming = = Note: â>â, â=â, and â<â denote that the HMA has a higher, comparable, or lower value, respectively, than the WMA technology in terms of the different material properties. Table F.15. Comparison of material properties between HMA and WMA pavements (MT I-15 project). Material Material Property HMA vs. WMA 2011 2014 14°F 68°F 86°F 14°F 68°F 86°F Mix Dynamic Modulus Evotherm = > = = = = Creep Compliance Evotherm = = = = > = Vertical Failure Deformation (68°F) Evotherm = = Fracture Work Density (14°F) Evotherm = > Rutting Resistance Index Evotherm > = Binder PG Evotherm < MSCR-R3.2 Evotherm = Fracture Energy (68°F) Evotherm < Failure Strain (41°F) Evotherm = = = = = Table F.16. Comparison of material properties between HMA and WMA pavements (TN SR 125 project). Material Material Property HMA vs. WMA 2011 2014 14°F 68°F 86°F 14°F 68°F 86°F Mix Dynamic Modulus Sasobit = > = > = >Evotherm = > = = = > Creep Compliance Sasobit = = = = = = Evotherm = = > = = = Vertical Failure Deformation (68°F) Sasobit =Evotherm = Fracture Work Density (14°F) Sasobit =Evotherm = Rutting Resistance Index Sasobit >Evotherm = Binder PG Sasobit =Evotherm = MSCR (R3.2) Sasobit >Evotherm = Fracture Energy (68°F) Sasobit >Evotherm = Failure Strain (41°F) Sasobit =Evotherm = = = = = > = = = > > = = = = Table F.17. Comparison of material properties between HMA and WMA pavements (IA US 34 project).
102 (a) HMA section (b) Sasobit section (c) Evotherm section (d) Foaming section Figure F.12. Distresses in MT I-15 project: (a) HMA section, (b) Sasobit section, (c) Evotherm section, and (d) Foaming section. Material Material Property HMA vs. WMA 2013 2015 14°F 68°F 86°F 14°F 68°F 86°F Mix Dynamic Modulus Sasobit = = = = = =Evotherm = = = = = > Creep Compliance Sasobit = = < = = =Evotherm = = < = = = Vertical Failure Deformation (68°F) Sasobit = = Evotherm = = Fracture Work Density (14°F) Sasobit Not Available = Evotherm Not Available > Rutting Resistance Index Sasobit = = Evotherm = = Binder PG Sasobit = =Evotherm = = MSCR (R3.2) Sasobit = > Evotherm < > Fracture Energy (68°F) Sasobit > = Evotherm = = Failure Strain (41°F) Sasobit = =Evotherm < = Note: âNot Availableâ indicates that no comparison could be made due to lack of data. Table F.18. Comparison of material properties between HMA and WMA pavements (LA US 61 project).
103 (a) HMA: reflective cracking (b) Sasobit: surface-initiated cracking (c) Evotherm: reflective cracking (d) Foaming: reflective cracking Figure F.13. Field cores drilled at the tip of transverse cracks (MT I-15). 0 20 40 60 80 100 120 140 160 Tr an sv er se C ra ck L en gt h, ft /2 00 ft Before Construction Second Round HMA Sasobit Evotherm Foaming 09/15/2011 08/14/2013 Figure F.14. Measured transverse crack lengths for the MT I-15 project. the Evotherm pavement had the highest transverse cracking number before construction, the Evotherm pavement did not reflect as much cracking as the other pavements, such as the HMA and Foaming pavements, which may be attributed to the high fracture work density of the Evotherm pavement. This result confirms that high fracture work density values indicate greater resistance to reflective cracking. TN SR 125 Project For the TN SR 125 project, Figures F.15 and F.16 provide an overview of the pavement conditions before construction, during construction, after construction, and 3 years after construction for the HMA and Evotherm pavements, respec- tively. Visual observation indicates that both the HMA and Evotherm pavements developed extensive cracking distresses
104 (a) Before Construction (b) During Construction (c) After Construction (d) 3 Years After Construction Longitudinal Cracking (Non-wheel path) Transverse Cracking Figure F.15. HMA pavement overview for the TN SR 125 project. Figure F.16. Evotherm pavement overview for the TN SR 125 project. (a) Before Construction (b) During Construction
105 Figure F.16. (Continued). (d) 3 Years After Construction(c) After Construction Longitudinal Cracking (Non-wheel path) Transverse Cracking before construction, although quantitative measurements of crack lengths are not available. Three years after construction, the pavement surface exhibited cracking again. Based on the field cores taken at the tip of cracks, as shown in Figure F.17, most cracks are reflective cracking. Note that only a tack coat was applied on the existing pavement surface before the over- lay was placed; no milling was conducted. Figures F.18 (a) and (b) present comparisons between the HMA and Evotherm pavements for the TN SR 125 project in terms of transverse cracking length and rut depth, respectively. The HMA pavement shows transverse cracking comparable with the Evotherm pavement. For the rut depths, no significant difference was found between HMA and Evotherm pavements. IA US 34 Project After 2 years of service, all the HMA, Sasobit, and Evotherm pavements in the IA US 34 project developed some degree of transverse cracking and rutting, as shown in Figure F.19. Field cores taken at the tips of transverse cracks, as shown in Figure F.20, indicate that most transverse cracking in the IA US 34 project was surface-initiated. (a) HMA: reflective cracking (b) Evotherm: reflective cracking Figure F.17. Field cores drilled at the tip of transverse cracks for the TN SR 125 project.
(a) Transverse Cracking Comparison 0.0 50.0 100.0 150.0 200.0 250.0 Tr an sv er se Cr ac k Le ng th , ft /2 00 ft HMA Evotherm Existing Overlay 10/24/2010 12/16/2014 (b) Rut Depth Comparison Existing Overlay 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 Ru tD ep th ,i n. HMA Evotherm 10/25/2011 12/16/2014 Figure F.18. Measured distress comparisons between HMA and Evotherm pavements for the TN SR 125 project. (a) HMA section (b) Sasobit section (c) Evotherm section Figure F.19. Field performance results for the IA US 34 project. (a) HMA (b) Sasobit (c) Evotherm Figure F.20. Field cores drilled at the tip of transverse cracks for the IA US 34 project.
107 (a) Transverse Crack 0 20 40 60 80 100 Tr an sv er se Cr ac k Le ng th , ft /2 00 ft HMA Sasobit Evotherm (b) Rut Depth 0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 Ru tD ep th ,i n. HMA Sasobit Evotherm Figure F.21. Distress comparisons between HMA and WMA pavements for the IA US 34 project. (a) HMA section (b) Sasobit section (c) Evotherm section Figure F.22. Field performances for the LA US 61 project. Figures F.21 (a) and (b) present the transverse cracking length and rut depth comparisons among the HMA, Sasobit, and Evotherm pavements, respectively. No significant dif- ferences in transverse cracking were found among the three pavements. The HMA pavement shows higher rut depth values than the Sasobit and Evotherm pavements. LA US 61 Project After 2 years of service in the field, the HMA, Sasobit, and Evotherm pavements of the LA US 61 project generally exhibited transverse cracking only, as shown in Figures F.22 (a), (b), and (c), and very low rut depth values. The field cores extracted at the tip of transverse cracks (Figure F.23) indicate that the cracks were surface-initiated. Figures F.24 (a) and (b) present comparisons of the trans- verse cracking length and rut depth, respectively, between HMA and WMA pavements. Based on the t-test results, no significant statistical difference in transverse cracking was found between the Sasobit and HMA pavements or between the Evotherm and HMA pavements, although by observation, the average crack length in the HMA pavements is higher than in the Evotherm pavements. Based on the comparison criterion of a rut depth difference of 1 â16 inch, the Sasobit and Evotherm pavements show comparable rutting performance with the corresponding HMA pavement.
108 (a) Transverse Crack 0.0 20.0 40.0 60.0 80.0 100.0 Tr an sv er se C ra ck L en gt h, ft /2 00 ft HMA Sasobit Evotherm 0.00 0.02 0.04 0.06 0.08 0.10 0.12 Ru t D ep th , i n. HMA Sasobit Evotherm (b) Rut depth Figure F.24. Field performance comparisons for the LA US 61 project. (a) HMA section (b) Sasobit section (c) Evotherm section Figure F.23. Field cores drilled at the tip of transverse cracks for the LA US 61 project.
