Performance-Based Mix Design for Porous Friction Courses (2018) / Chapter Skim
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From page 50... ...
50 Introduction Three aggregate types (limestone, traprock, and granite) were evaluated in Part 1.
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Part 1: Evaluation of Mix Designs 51 Mix Design Component Florida Florida New Jersey Virginia Georgia South Carolina Mixture Designation Good (cracking) Poor (cracking)
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52 Performance-Based Mix Design of Porous Friction Courses added to the poor design in order to match the gradation of the original poor blend; therefore, the only real difference in the adjusted blends was the difference in binder type. Instead of using the 6.0% AC stated on the JMF for the Florida poor mix, it was decided to use the same AC as the good design (7.1%)
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Part 1: Evaluation of Mix Designs 53 Mix Design Designation p-Value Difference Georgia Good 0.426 Insignificant South Carolina Poor 0.818 Insignificant Florida Good 0.756 Insignificant Florida Poor 0.019 Significant Virginia Poor 0.126 Insignificant New Jersey Good 0.480 Insignificant Table 20. Cantabro conditioned vs.
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54 Performance-Based Mix Design of Porous Friction Courses only specimens to pass the ASTM recommended 20% maximum loss criterion. If the AASHTO criterion (15%)
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Part 1: Evaluation of Mix Designs 55 An analysis of variance (ANOVA) analysis (α = 0.05)
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56 Performance-Based Mix Design of Porous Friction Courses Mix ID Total AC (%)
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Part 1: Evaluation of Mix Designs 57 requirement. Since New Jersey and Virginia require the VCA calculation to be incorporated in their designs, the failing VCA ratios seemed to be an error.
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58 Performance-Based Mix Design of Porous Friction Courses design is a 9.5 mm NMAS mix, this seemed appropriate. The results provide a decrease in the VCA ratio to a value of 0.92, which passes the recommended criterion.
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Part 1: Evaluation of Mix Designs 59 unexpected when fabricating PFC specimens. A change in VMA of less than 1.0% for a design shows no relative change to the mixture.
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60 Performance-Based Mix Design of Porous Friction Courses Performance Testing Draindown The draindown testing was performed on all of the JMF designs using a 2.36 mm (#8) mesh basket.
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Part 1: Evaluation of Mix Designs 61 Figure 46. Part 1 HWTT results.
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62 Performance-Based Mix Design of Porous Friction Courses Moisture Susceptibility Testing The moisture susceptibility testing for Part 1 provided both indirect tensile strength (ITS) of the conditioned and unconditioned specimens, along with the TSR for each mixture.
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Part 1: Evaluation of Mix Designs 63 Based on unconditioned strengths, it can be seen that there is a gap between the mean strength of the mixtures. The New Jersey, Georgia, and Florida poor designs have strengths greater than 70 psi, while the Virginia, Florida good, and South Carolina designs have strengths of less than 60 psi.
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64 Performance-Based Mix Design of Porous Friction Courses Figure 48 shows that there is a relationship between air voids and shear strength (R2 = 0.60) such that the shear strength of the mix decreases as air voids increase.
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Part 1: Evaluation of Mix Designs 65 There was a single outlier in three of the specimen sets. Since there were at least four samples tested per mix design, this left at least three specimens on which statistical analysis could be performed.
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66 Performance-Based Mix Design of Porous Friction Courses I-FIT The I-FIT procedure was used to determine the mixture susceptibility to intermediate temperature cracking. While most dense-graded mixtures have an FI ranging from 0 to 20, the values for the PFC mixtures were much larger due to the large slope, post-peak.
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Part 1: Evaluation of Mix Designs 67 1.694 1.263 1.556 1.297 1.255 1.582 0.000 0.500 1.000 1.500 2.000 2.500 Georgia Good South Carolina Poor Florida Poor Florida Good Virginia Poor New Jersey - Good kN Figure 50. Part 1 I-FIT -- average peak load.
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68 Performance-Based Mix Design of Porous Friction Courses Wet Track Abrasion The Wet Track Abrasion Test was originally performed according to the ISSA TB-100 test procedure and the specimens were submerged in water and tested for 5.25 minutes. This produced no visible wear on the specimen, so the testing time was increased to 30 minutes.
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Part 1: Evaluation of Mix Designs 69 shows a difference in the mixtures. From the results of the ANOVA (Table 36)
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70 Performance-Based Mix Design of Porous Friction Courses Mix ID Peak Load N Mean Grouping Florida - Poor 5 3.286 A Georgia - Good 5 3.111 A New Jersey - Good 6 2.951 A Virginia - Poor 5 2.295 B Florida - Good 6 2.057 B C South Carolina - Poor 6 1.645 C p < 0.001 R2 = 83% Table 36. ANOVA for Peak load of Part 1 no-notch I-FIT specimens.
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Part 1: Evaluation of Mix Designs 71 Mix ID FI N Mean Grouping South Carolina - Poor 6 62.7 A Virginia - Poor 5 49.6 A B New Jersey - Good 6 36.1 B C Georgia - Good 5 21.6 C Florida - Poor 5 21.1 C Florida - Good 6 19.5 C p < 0.001 R2 = 72% Table 38. ANOVA for FI of Part 1 no-notch I-FIT specimens.
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72 Performance-Based Mix Design of Porous Friction Courses 23.5 27.9 57.5 57.7 28.7 35.6 21.1 19.5 49.6 62.7 21.6 36.1 0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 FL Poor FL Good VA Poor SC Poor GA Good NJ Good Av er ag e Fl ex ib ili ty In de x FI - Notch FI - No Notch Figure 59. I-FIT notch versus no-notch comparison for FI.
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Part 1: Evaluation of Mix Designs 73 All of the designs when analyzed for peak load were significantly different. All of the designs except Florida poor were also significantly different for the Gf.
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