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From page 103... ... 103 PFC mixtures have been utilized to improve safety and reduce pavement noise and other environmental impacts. These applications are closely related to their high air void content and open-graded aggregate gradation. Read the entire page →
From page 104... ... 104 Performance-Based Mix Design of Porous Friction Courses measured in this study were based on the CoreLok method, which generally results in about 2% less air voids. Three of the designs in this study, the Georgia design and the two Florida designs, had a design air void content below 18%; however, all of the designs were above 15%. Read the entire page →
From page 105... ... Performance-Based Mix Design Procedure 105 did not distinguish between well and poorly performing designs. The Florida designs and the Georgia design had VMA values of approximately 26%, while the New Jersey, South Carolina, and Virginia designs had VMA of approximately 32%. Read the entire page →
From page 106... ... 106 Performance-Based Mix Design of Porous Friction Courses aggregate in the PFC designs, the data showed no significant difference in VCA ratio. VCA testing also seems impractical for PFC mixtures, since these mixtures are often placed at less than the thickness of two aggregate particles of maximum size. Read the entire page →
From page 107... ... Performance-Based Mix Design Procedure 107 Draindown As shown in Table 89, none of the standard designs in this study exhibited draindown using a No. 8 mesh basket. Read the entire page →
From page 108... ... 108 Performance-Based Mix Design of Porous Friction Courses 0.70 and ASTM specifies a minimum of 0.80. This study shows that the TSR alone is not a good predictor of performance, since the Virginia poor design had a higher TSR value than the New Jersey and Georgia good designs. Read the entire page →
From page 109... ... Performance-Based Mix Design Procedure 109 the peak load needed to shear a sample was determined and divided by the cross-sectional area of the specimen. This is a procedure that is easy to run and will not involve costly equipment since it is performed on a Marshall press commonly available in mix design laboratories. Read the entire page →
From page 110... ... 110 Performance-Based Mix Design of Porous Friction Courses mix designs in the modified no-notch I-FIT testing was similar to that of the unconditioned ITS. The peak load for the South Carolina poor, Florida good, and Virginia poor designs was less than 2.300 kN, while the Georgia good, New Jersey good, and Florida poor designs had peak loads greater than 2.900 kN. Read the entire page →
From page 111... ... Performance-Based Mix Design Procedure 111 raveling and one failed due to cracking and were replaced within 8 years. The other three mixtures showed good performance and lasted up to 19 years in the field. Read the entire page →
From page 112... ... 112 Performance-Based Mix Design of Porous Friction Courses The key mixture properties and performance tests evaluated in Part 1 of this research were utilized in other experiments later in this study to evaluate the effects of added P-200 material, binder modification, and layer thickness on the performance of PFC mixtures. The results of these experiments are summarized in the following sections. Read the entire page →
From page 113... ... Performance-Based Mix Design Procedure 113 Durability and Rutting Resistance The Cantabro, splitting tensile strength, and Hamburg test results are shown in Table 103, Table 104, and Table 105, respectively. The results showed improvement over the control mix design when the additional P-200 material was added as follows: • Adding more P-200 material to the mix designs reduced the Cantabro loss. Read the entire page →
From page 114... ... 114 Performance-Based Mix Design of Porous Friction Courses Cracking Resistance The OT data in Table 106 show an increase in cycles to failure with additional P-200 for both the Georgia and South Carolina mix designs. Based on these results, it may be possible to improve resistance to reflective cracking by increasing the cohesiveness of the mixture. Read the entire page →
From page 115... ... Performance-Based Mix Design Procedure 115 Mix ID Proposed Design Requirement Results Improvement Over Control Georgia Control 200 min. (Needs Further Validation) Read the entire page →
From page 116... ... 116 Performance-Based Mix Design of Porous Friction Courses research study indicates that specifying a gradation band of 2% to 6% will provide a potential for more durable mixes. Effect of Fiber The effect of fiber was evaluated based on the Georgia mix design. Read the entire page →
From page 117... ... Performance-Based Mix Design Procedure 117 may be increasing the mixture stiffness or reducing the elastic recovery of the mixture and therefore decreasing the cracking resistance of the design. Since the fiber stabilizer appeared to stiffen and improve strength of the mixture, it was not surprising that the flexibility of mix with the fiber was reduced. Read the entire page →
From page 118... ... 118 Performance-Based Mix Design of Porous Friction Courses Durability and Rutting Resistance Table 113, Modified mixes without fiber had lower unconditioned tensile strength than the Control mix. This resulted in higher TSR values and is why TSR alone is not a sufficient criteria for evaluating resistance to moisture damage. Read the entire page →
From page 119... ... Performance-Based Mix Design Procedure 119 Mix ID Proposed Design Requirement Results Improvement Over Control Georgia Control 20 max. 19.3 Georgia PG 76-22 SBS 12.3 Yes Georgia PG 76-22 GTR 12.1 Yes Georgia PG 82-22 SBS 4.7 Yes Table 113. Read the entire page →
From page 120... ... 120 Performance-Based Mix Design of Porous Friction Courses HiMA design failing the draindown criteria, the addition of fiber or an alternative stabilizing agent will be needed. HiMA is significantly more expensive than standard SBS binders, and therefore it may not be economical to choose the HiMA over the SBS binder. Read the entire page →
From page 121... ... Performance-Based Mix Design Procedure 121 • Optimum binder content is determined for the selected gradation to meet the air void, Cantabro loss, and permeability criteria that are required to achieve the functional capability of a PFC mixture, as shown in Table 2 of the revised procedure (Appendix A) Read the entire page →

From page 103...

... 103 PFC mixtures have been utilized to improve safety and reduce pavement noise and other environmental impacts. These applications are closely related to their high air void content and open-graded aggregate gradation.