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50 Figure 43. LMH Regression results of and for AC over AC pavement and Wet-No Freeze climate zone. there were not enough sections to separate the sections into The details of each set of model calibration coefficients are two categories (calibration sections and validation sections). given in Appendix N. The approach taken raises concern about how well the cal- Figure 45 shows the predicted versus observed values and ibrated predictions match the field data. The next section dis- for HMA overlays over a cracked asphalt pavement surface cusses that concern. in a Wet-Freeze Zone. Figure 46 shows the predicted versus the observed values of and for HMA overlays over jointed concrete pavements Calibrated Results Compared in a Wet-Freeze Zone. with Observed Field Data Figure 47 shows the predicted versus the observed values The details of each set of calibration coefficients are pro- of and for HMA overlays with reinforcing interlayers over vided in Appendices L, M, and N. The scale and shape param- cracked asphalt pavement surfaces in a Dry-Freeze Zone. eters and that were fit to the field observations are Figure 48 shows the predicted versus observed values of provided in Appendix M, and the calibration coefficients and and for HMA overlays with reinforcing interlays over plots of the predicted versus the observed values of and jointed concrete pavements in a Wet-No Freeze Zone. are provided in Appendix N. Some of the difference between the predicted and the observed distress in these figures is due to the difference in levels of construction quality control. Calibration Coefficients by Regression Analysis Predictions of Overlay Figure 43 shows the predicted versus observed values of Reflection Cracking and for HMA overlays over a cracked asphalt surface in a Wet-No Freeze zone. Eleven sets of calibration coefficients were developed, one Figure 44 shows the predicted versus the observed values set for each combination of pavement structure and climatic of and for a HMA overlay placed over a cracked asphalt zone for which sufficient data were available. Each set of pavement surface in the Dry-No Freeze zone. model calibration coefficients have a maximum of three pairs Figure 44. MH Regression results of and for AC over AC pavement and Dry-No Freeze climate zone.

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51 Figure 45. MH Regression results of and for AC over AC pavement and Wet-Freeze climate zone. Figure 46. H Regression results of and for AC over JPC/JRC pavement and Wet-Freeze climate zone. Figure 47. LMH Regression results of and for AC with reinforcing over AC pavement and Dry-Freeze climate zone. Figure 48. LMH Regression results of and for AC with Reinforcing over PCC pavement and Wet-No Freeze climate zone.

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52 Table 25. Figures of calculated reflection cracking distress curves. Figure Number Overlaid Pavement Type Climate Zone Distress Severity Levels 49 Asphalt WF L, M. H 50 Jointed Reinforced Concrete WF L, M, H 51 Friction Course over Asphalt WF L, M, H 52 Continuously Reinforced WF L, M Concrete 53 Reinforcing Geosynthetic W-NF L over Jointed Concrete 54 Reinforcing Geosynthetic DF L Over Asphalt 55 Asphalt W-NF L, M 56 Friction Course Over Asphalt W-NF L 57 Asphalt DF L, M, H 58 Asphalt D-NF L, M, H 59 Reinforcing Geosynthetic WF L, M Over Jointed Concrete of and values corresponding to the three levels of distress jointed reinforced concrete pavement in a Wet-Freeze Zone severity. In some cases, there were no observed high or medium (Beaver, Pennsylvania). The High level of severity remains low severity distress levels. Thus data were available for 24 out of a for a long time before beginning its sharp rise. The difference total of 33 possible sets of model calibration coefficients. The between the rates of distress development shown in Figures 49 24 sets of calibration coefficients are tabulated and graphs and 50 is due mainly to the difference in thermal stresses. of the observed versus the predicted values of and are Figure 51 shows the predicted development of transverse presented in Appendix N. Figures 49 through 59 present reflection cracking and severity of an HMA overlay over an 11 sample sets of calculated distress curves, one for each of open graded friction course which was used as a strain reliev- the pavement structure and climatic zone combinations, as ing interlayer over a cracked asphalt pavement surface in a listed in Table 25. Wet-Freeze Zone (Frederick, Maryland). Figure 49 shows the predicted development of transverse Figure 52 shows the predicted development of transverse reflection cracking (at the L-M-H, M-H, and H levels of sever- reflection cracking and severity of an HMA overlay over a ity) for an HMA overlay over a cracked asphalt pavement sur- continuously reinforced concrete pavement surface in a Wet- face in a Wet-Freeze Zone (Lincoln, Maine). The H level of Freeze Zone (Minnesota, Washington). The figure indicates severity begins to appear at around 100 days of service life. no observed high severity reflection cracks. Figure 50 shows the predicted development of transverse Figure 53 shows the predicted development of transverse reflection cracking and severity for an HMA overlay over a reflection cracking and severity of an HMA overlay reinforced 80 90 70 80 % Total Length of Cracks % Total Length of Cracks 60 70 50 60 L+M+H 50 L+M+H 40 M+H 40 M+H 30 H 30 H 20 100/e 100/e 20 10 10 0 0 0 200 400 600 800 0 1000 2000 3000 4000 5000 No. of Days No. of Days Figure 49. Development of transverse reflection Figure 50. Development of transverse reflection cracking distress extent and severity for HMA cracking distress extent and severity for HMA overlay over asphalt surface in wet-freeze zone overlay over jointed reinforced concrete in (Lincoln, Maine). wet-freeze zone (Beaver, Pennsylvania).

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53 90 100 80 90 % Total Length of Cracks 80 % Total Length of Cracks 70 60 70 60 50 L+M+H L+M+H 50 40 M+H M+H (Not calibrated) 40 30 H H (Not calibrated) 30 20 100/e 100/e 20 10 10 0 0 0 1000 2000 3000 4000 5000 0 1000 2000 3000 No. of Days No. of Days Figure 51. Development of transverse reflection Figure 54. Development of transverse reflection cracking distress extent and severity for HMA cracking distress extent and severity for HMA overlay overlay over friction course over asphalt surface with reinforcing geosynthetic over asphalt surface in wet-freeze zone (Frederick, Maryland). in dry-freeze zone (Amarillo, Texas). 70 with a geosynthetic material and placed over a jointed con- crete pavement in a Wet-No Freeze Zone (Waco, Texas). 60 Because medium or high levels of severity were not observed % Total Length of Cracks 50 during the monitoring period, only the low level of severity 40 L+M+H could be modeled. 30 M+H Figure 54 shows the predicted development of transverse H (Not calibrated) reflection cracking and severity of an HMA overlay reinforced 20 100/e with a geosynthetic material and placed on a cracked asphalt 10 pavement surface in a Dry-Freeze Zone (Amarillo, Texas). No 0 medium or high level severity distress was observed on any of 0 2000 4000 6000 8000 10000 the test sections during the monitoring period. No. of Days Figure 55 shows the predicted development of transverse Figure 52. Development of transverse reflection reflection cracking and severity of an HMA overlay over a cracking distress extent and severity for HMA overlay cracked asphalt pavement surface in a Wet-No Freeze Zone over continuously reinforced concrete pavement (Pittsylvania, Virginia). The low severity distress appeared in wet-freeze zone (Minnesota, Washington). after about 1800 days and medium level severity began to 120 90 80 100 % Total Length of Cracks % Total Length of Cracks 70 60 80 50 L+M+H L+M+H 60 40 M+H M+H (Not calibrated) 40 H (Not calibrated) 30 H (Not calibrated) 100/e 20 100/e 20 10 0 0 0 1000 2000 3000 0 500 1000 1500 2000 No. of Days No. of Days Figure 53. Development of transverse reflection Figure 55. Development of transverse reflection cracking distress extent and severity for HMA overlay cracking distress extent and severity for HMA with reinforcing geosynthetic over jointed concrete overlay over asphalt surface in wet-no freeze zone in wet-no freeze zone (Waco, Texas). (Pittsylvania, Virginia).

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54 120 100 90 100 80 % Total Length of Cracks % Total Length of Cracks 80 70 L+M+H 60 60 L+M+H M+H (Not calibrated) 50 M+H H (Not calibrated) 40 40 H 100/e 30 100/e 20 20 10 0 0 1000 2000 3000 4000 0 0 2000 4000 6000 No. of Days No. of Days Figure 56. Development of transverse reflection Figure 58. Development of transverse reflection cracking distress extent and severity for HMA cracking extent and severity for HMA overlay over overlay over friction course over asphalt surface asphalt pavement surface in dry-no freeze zone in wet-no freeze zone (Yazoo, Mississippi). (Pinal, Arizona). appear after about six years; no high level severity distress cracked asphalt pavement surface in a Dry-No Freeze Zone was observed. (Pinal, Arizona). The medium level severity of distress appeared Figure 56 shows the predicted development of transverse and began its sharp rise after about 12 years. reflection cracking and severity of an HMA overlay over an Figure 59 shows the predicted development of transverse open graded friction course which was used as a strain relieving reflection cracking and severity of an HMA overlay with geo- interlayer over a cracked asphalt pavement surface in a Wet-No synthetic reinforcing over a jointed concrete pavement surface Freeze Zone (Yazoo, Mississippi). Only the low level severity of in a Wet-Freeze Zone (New York City). No high level severity distress was observed. distress was observed. Figure 57 shows the predicted development of transverse Figures 49 through 59 illustrate the predictions for each of reflection cracking and severity of an HMA overlay over a the sets of reflection cracking model calibration coefficients. cracked asphalt pavement surface in a Dry-Freeze Zone (Deaf Each of the four major climatic zones are represented, but not Smith County, Texas). The high, medium, and low levels of all of the pavement structure-overlay types are. Although 11 distress severity appeared within the first year. sets of calibration coefficients were developed, a total of 40 Figure 58 shows the predicted development of transverse combinations are possible (four climatic zones and 10 pave- reflection cracking and severity of an HMA overlay over a ment structure-overlay types). All of these additional sets of 90 120 80 % Total Length of Cracks 70 100 % Total Length of Cracks 60 80 50 L+M+H L+M+H 40 M+H 60 M+H H (Not calibrated) 30 H 100/e 40 20 100/e 10 20 0 0 0 1000 2000 3000 4000 0 100 200 300 400 500 600 No. of Days No. of Days Figure 59. Development of transverse reflection Figure 57. Development of transverse reflection cracking distress extent and severity for HMA cracking extent and severity for HMA overlay overlay with reinforcing geosynthetic over over asphalt pavement surface in dry-freeze zone jointed concrete pavement in wet-freeze zone (Deaf Smith County, Texas). (New York, New York).