Performance-Based Mix Design for Porous Friction Courses (2018) / Chapter Skim
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Pages 40-49
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40 Introduction In order to have a well performing design, the PFC mixture must have a high enough air void content to achieve the permeability required for water to drain through and away from the pavement surface. Along with performance tests to evaluate durability and cracking concerns, testing was conducted to determine volumetric properties and permeability of the mixtures.
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From page 41... ...
Methodology 41 100 Equation 3VCA G G DRC ca w s ca w = γ − γ γ ∗ 100 Equation 4VCA G P G MIX mb ca ca = − ∗ where VMA = voids in mineral aggregate VCADRC = voids in coarse aggregate in dry-rodded condition VCAMIX = voids in coarse aggregate of the compacted mixture Gsb = combined bulk specific gravity of the total aggregate Ps = percent of aggregate in the mixture γs = unit weight of the coarse aggregate fraction in the dry-rodded condition (kg/m3) γw = unit weight of water (998 kg/m3)
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From page 42... ...
42 Performance-Based Mix Design of Porous Friction Courses thick binder film in place. Cellulose or mineral fibers are the most common stabilizing agents and are very effective in preventing draindown.
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Methodology 43 The specimens were subjected to a load of 158 ± 1 lb produced by a solid steel wheel and extra weights. The specimens were submerged and conditioned in a 50°C water bath for 30 minutes prior to testing.
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44 Performance-Based Mix Design of Porous Friction Courses performance grade. All of the mix designs with the exception of the Part 2 mix with PG 82-22 were produced with a PG 76-22.
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Methodology 45 void properties of the compacted specimens were determined prior to shearing in order to determine if a relationship between cohesive strength and air voids exists. A device developed to determine bond strength of tack coats at the interface of pavement layers (Figure 33)
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46 Performance-Based Mix Design of Porous Friction Courses mix design. In order to provide accurate results, three consecutive runs had to be within 4.0% of each other.
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Methodology 47 take place prior to the 1,200 cycles, and the test was allowed to run for 2,000 cycles to determine the failure point. Some specimens still did not fail prior to 2,000 cycles, and the data were extrapolated to predict the cycles at which the specimen would have reached the 93% reduction.
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From page 48... ...
48 Performance-Based Mix Design of Porous Friction Courses accounts for the vibration and allows the notch width to be within specification. The specimens are conditioned in an environmental chamber for 2 ± 0.5 hours at 25°C ± 0.5°C prior to testing.
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From page 49... ...
Methodology 49 Equation 9Area r a tlig ( ) = − ∗ where Gf = fracture energy (Joules/m2)
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