AASHTO PP 77-14 pdf free download
AASHTO PP 77-14 pdf free download.Materials Selection and Mixture Design of Permeable Friction Courses (PFCs).
3. TERMINOL OGY 3.1. Definitions: 3.1.1. asphalt binder- -an asphalt-based cement that is produced from petroleum residue either with or without the addition of modifiers. 3.1.2. abrasion loss- -the loss of mass from an asphalt mixture specimen under the effect of abrasion. 3.1.3. air voids- -the total volume of the small pockets of air between the coated aggregate particles throughout a compacted paving mixture, expressed as a percent of the total volume of the compacted specimen. 3.1.4. breakpoint sieve- the finest sieve to retain at least 10 percent of the aggregate fraction. 3.1.5. draindown- -separation of asphalt binder from the coarse aggregate structure, generally during storage Or transportation. 3.1.6. permeable friction course (PFC)- a special type of porous asphalt mixture with air voids of at least 18 percent used for reducing hydroplaning and potential for loss of friction resistance, where the function of the mixture is to provide a free-draining layer that permits surface water to migrate laterally through the mixture to the edge of the pavement. 3.1.7. stabilizing additive- materials used to minimize draindown of asphalt during transport and placement of PFC, which may include fibers, polymers, crumb rubber, or a combination of these additives. 3.1.8. voids in the coarse aggregate (VCA)- -the volume of voids between the coarse aggregate particles, where this volume includes filler, fine aggregate, air voids, asphalt binder, and stabilizing additives, if used.
4. SUMMARY OF PRACTICE 4.1. Aggregates, asphalt binder, and stabilizing additives are selected that meet specification values. Trial aggregate blend gradations are selected and tested to determine the design aggregate gradation. The blends are compacted using a trial binder content in order to evaluate the trial mixes and select the design gradation to ensure stone- on-stone contact. Once a trial gradation is selected, the asphalt binder content is altered and the optimum asphalt binder content is selected based on meeting minimum binder content and air void requirements and ensuring stone-on-stone contact in the mixture. Stone-on-stone content is verified by ensuring the volume of voids in the mixture is less than or equal to the volume of voids in the dry-rodded coarse aggregate fraction of the design gradation. The mix design is further verified by determining the abrasion loss, which is used as an indicator of the durability of the mixture. The designed mixture is then evaluated for resistance to moisture susceptibility.
6.1.3. Asphalt Binders- Performance-graded asphalt binders meeting the requirements of M 320 are selected based on the climate and traffic. Because of the relatively high binder contents and open grading of the aggregate, a stiff asphalt binder is needed to ensure durability. Therefore, for high- volume roadways or pavements with slow to standing traffic, select the asphalt binder high- temperature grade two grades higher than the asphalt binder grade required for the climate. (See Note 1.) Select the high-temperature binder grade one grade higher than the climatic grade for all other roadways. Note 1- Some southern states successfully use a PG 76 asphalt binder for high-volume roadways, which is only one grade higher.
6.1.4. Stabilizing Additives- Stabilizing additives are needed to prevent draindown of asphalt binder from the coarse aggregate skeleton during transportation and placement. Stabilizing additives such as cellulose fiber, mineral fiber, crumb rubber, and polymers have been used to minimize draindown potential. AASHTO PP 77-14 pdf download.
