AASHTO R 46-08 pdf free download

AASHTO R 46-08 pdf free download.Designing Stone Matrix Asphalt (SMA).
3. TERMINOL .OGY 3.1. Definitions: 3.1.1. stone matrix asphalt (SMA)- -an asphalt mixture consisting of two parts, a coarse aggregate skeleton and a rich asphalt binder mortar. The mixture must have an aggregate skeleton with coarse aggregate-on-coarse aggregate contact (generally referred to as stone-on-stone contact). The coarse aggregate is generally considered to be that fraction of the aggregate retained on the 4.75-mm (No.4) sieve but may be designated as other sizes. 3.1.2. air voids (Va)- -the total volume of the small pockets of air between the coated aggregate particles throughout a compacted asphalt mixture, expressed as a percent of the bulk volume of the compacted asphalt mixture (Note 1). Note 1- Term defined in the Asphalt Institute Publication MS-2. 3.1.3. voids in the mineral aggregate (VMA)- the volume of the intergranular void space between the aggregate particles of a compacted asphalt mixture that includes the air voids and the effective binder content, expressed as a percent of the total volume of the specimen (Note 1). 3.1.4. voids in the coarse aggregate (VCA)- the volume between the coarse aggregate particles. This volume includes filler, fine aggregate, air voids, asphalt binder, and stabilizing additive (if used). 3.1.5. SMA mortar- a mixture of asphalt binder, fllr [material passing the 0.075-mm (No. 200) sieve], and stabilizing additive. 3.1.6. stabilizing additive- either cellulose or mineral fiber.4. SUMMARY OF THE PRACTICE 4.1. Materials Selection- Asphalt binder, aggregate, mineral fillers, and stabilizing additives that meet the applicable specification are selected. 4.2. Selecting Optimum Gradation- -Three recommended trial aggregate gradations from the selected aggregates are blended. The dry-rodded unit weight for the coarse aggregate for each trial gradation is determined in accordance with T 19M/T 19. For each trial gradation, an initial trial asphalt binder content is selected and at least two specimens are compacted in accordance with T 312. Where no previous history is available, an initial trial asphalt binder content between 6.0 and 6.5 percent is recommended. Gradations of the three blends are selected to ensure that minimum V M A requirements and stone-on-stone contact are achieved. 4.3. Selecting Design Binder Content- Replicate specimens are compacted in accordance with T 312 at three binder contents. The design binder content is selected on the basis of satisfactory conformance with the requirements of Section 10 (Note 2). Note 2- When an SMA mix cannot be designed within the minimum binder content requirements, the guidelines given in Table X2. l can be used to establish minimum binder content requirements based on the combined-aggregate bulk specific gravity. 4.4. Evaluating Moisture Susceptibility- The moisture susceptibility of the mixture, designed and compacted in accordance with T 312 toa Va content of 6.0土1.0 percent, is evaluated in accordance with T 283.6. SEL .ECTION OF TRIAL GRADATIONS 6.1. The trial gradations must be selected to be within the desired specification range as defined in M 325. To design an SMA mixture, it is recommended that at least three trial gradations be initially evaluated. It is suggested that one of the trial blends fall along the coarse limits, one along the fine limits, and one in the middle of the gradation bands as defined in M 325. When the bulk specific gravities of the different aggregates to be used in the mixture vary by more than 0.2, the trial blend gradations should be based on volumetric percentage. An example problem ilustrating how to blend aggregates based on volume is given in Appendix X1.1.AASHTO R 46-08 pdf download.