Evaluation of Bonded Concrete Overlays on Asphalt Pavements (2022) / Chapter Skim
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From page 89... ...
89 Several BCOA design methods have been developed over the past two decades, including BCOA-ME, the Colorado DOT method, the Illinois DOT method, and PaveME. One of the first design methods included the ACPA BCOA Thickness Designer program; however, this program is no longer supported and has been excluded from discussion and further analysis for this study.
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Figure 70. Screenshot of BCOA-ME.
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Input Criteria General information Latitude, longitude, and elevation Design-lane ESALs Maximum allowable percentage of slabs cracked and reliability (25% cracked slabs and 85% reliability recommended) Climate Annual mean daily average temperature region ID Map of sunshine zone Existing structure Post-milling asphalt pavement layer thickness Asphalt layer fatigue (adequate or marginal)
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92 Evaluation of Bonded Concrete Overlays on Asphalt Pavements Illinois DOT The Illinois DOT design method was developed in 2008 in cooperation with the University of Illinois Urbana–Champaign (Roesler et al.
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Performance Prediction 93 The design method failure criteria, not modifiable by the user, include 20% slab cracking at 85% reliability. This method considers BCOA designs applicable for traffic levels below 5 million ESALs.
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94 Evaluation of Bonded Concrete Overlays on Asphalt Pavements Current BCOA design methods present several major limitations: • None of the design methods explicitly models the concrete–asphalt bond. Two introduce a partial bond and increase the concrete slab stress by a constant factor (Colorado and Illinois DOT)
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Performance Prediction 95 (Figure 74)
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96 Evaluation of Bonded Concrete Overlays on Asphalt Pavements 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 0.001 0.01 0.1 1 10 100 BC O A Th ic kn es s ( in ch ) ESALs (millions)
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Performance Prediction 97 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 400 500 600 700 800 900 BC O A Th ic kn es s ( in ch ) Flexural Strength (psi)
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98 Evaluation of Bonded Concrete Overlays on Asphalt Pavements The BCOA thickness is not influenced by asphalt layer thicknesses less than 7 in. An increase in asphalt layer thickness from 7 to 10 in.
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Performance Prediction 99 Flexural strength values ranging from 450 to 700 psi resulted in the maximum BCOA layer thickness (Figure 80)
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100 Evaluation of Bonded Concrete Overlays on Asphalt Pavements slabs, the maximum overlay thickness is reached at 10,000 ESALs and the minimum BCOA layer thickness is unchanged regardless of ESALs for 4- × 4-ft slabs (for range evaluated)
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Performance Prediction 101 In summary, the Illinois DOT design method is sensitive to changes in asphalt layer thickness, traffic factor, and MOR. The Illinois DOT design method is fairly insensitive to changes in k-value.
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102 Evaluation of Bonded Concrete Overlays on Asphalt Pavements from 4 to 8 in. (Figure 85)
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Performance Prediction 103 0 20 40 60 80 100 0 1,000 2,000 3,000 4,000 5,000 Lo ng itu di na l C ra ck in g (% sl ab s) Average Annual Daily Truck Traffic 4-inch 5x5 4-inch 8x8 6-inch 5x5 6-inch 8x8 8-inch 5x5 8-inch 8x8 Figure 86.
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104 Evaluation of Bonded Concrete Overlays on Asphalt Pavements Input % Change in BCOA Thickness over Evaluated Input Rangea BCOA-ME Colorado DOT Illinois DOT 4- x 4-ft 6- x 6-ft 12- x 12-ft All 4- x 4-ft 6- x 6-ft Nob Yes No Yes No Yes No No Yes No Yes Asphalt thickness −0.6 −1.7 −1.3 −0.3 −0.3 0.0 −1.1 −0.9 −1.8 −3.0 −3.1 ESALs 2.0 0.8 1.3 0.0 0.9 0.0 2.1 2.4 0.0 2.4 1.8 k-value −0.1 0.0 −1.0 0.0 −1.6 0.0 −3.1 −0.7 0.0 −0.4 0.0 Flexural strength −1.3 −1.6 −3.6 −1.1 −1.1 −0.5 −2.0 −3.1 −2.4 −3.1 −3.1 a Negative values represent a decrease in BCOA thickness over the evaluated input range. b No = excludes synthetic macrofibers; Yes = includes synthetic macrofibers.
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Performance Prediction 105 however, BCOA-ME results in less than half the BCOA layer thickness when synthetic macro bers are used. Increasing k-value for the Colorado DOT design method causes a signi cant reduction in BCOA thickness (approximately 3 in.)
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106 Evaluation of Bonded Concrete Overlays on Asphalt Pavements and thicker overlays (6 and 8 in.) , no change in longitudinal cracking is seen, excluding an increase in concrete flexural strength, over the range of values evaluated.
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Performance Prediction 107 (a)
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108 Evaluation of Bonded Concrete Overlays on Asphalt Pavements (a)
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Performance Prediction 109 (a)
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110 Evaluation of Bonded Concrete Overlays on Asphalt Pavements (a)
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Performance Prediction 111 (a)
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112 Evaluation of Bonded Concrete Overlays on Asphalt Pavements (a)
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Performance Prediction 113 (a)
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114 Evaluation of Bonded Concrete Overlays on Asphalt Pavements (a)
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Performance Prediction 115 (a)
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116 Evaluation of Bonded Concrete Overlays on Asphalt Pavements (a)
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Performance Prediction 117 (a)
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118 Evaluation of Bonded Concrete Overlays on Asphalt Pavements Figure 102. Design method results for (a)
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Performance Prediction 119 Figure 103. Design method results for (a)
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120 Evaluation of Bonded Concrete Overlays on Asphalt Pavements Figure 104. Design method results for (a)
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Performance Prediction 121 Figure 105. Design method results for (a)
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122 Evaluation of Bonded Concrete Overlays on Asphalt Pavements Figure 106. Design method results for (a)
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Performance Prediction 123 Figure 107. Design method results for (a)
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124 Evaluation of Bonded Concrete Overlays on Asphalt Pavements Figure 108. Design method results for (a)
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Performance Prediction 125 Figure 109. Design method results for (a)
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126 Evaluation of Bonded Concrete Overlays on Asphalt Pavements Table 60. Design procedure results.
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Performance Prediction 127 Figure 110. PaveME-predicted versus field-observed longitudinal cracking for all projects.
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128 Evaluation of Bonded Concrete Overlays on Asphalt Pavements field-observed longitudinal cracking (in percentage of slabs)
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