AASHTO PP 104:2021 Standard Practice for Sample Preparation and Polishing of Asphalt Mixture Specimens for Dynamic Friction Testing.
6.3.4. Spade the combined asphalt mixture batches with a large trowel until the asphalt mixture is a relatively uniform depth. Level the asphalt mixture with the trowel, taking care not to segregate the particles. Each asphalt mixture batch should be kept in the vicinity of the quadrant in which it was poured.
6.3.5. Place another piece of non-stick paper on top of the leveled asphalt mixture.
6.3.6. Compact the asphalt mixture until desired height is achieved.
6.3.7. Remove the non-stick paper from the top of the slab.
6.3.8. Slide the mold onto a counter and let it cool in front of a fan for a minimum of one hour before removing the mold. Do not handle the slab before it reaches room temperature.
6.3.9. Once the slab has cooled to room temperature, depending on the compaction method, dernold and flip the slab over and remove the non-stick paper from the bottom.
6.3.10. Depending on the compaction method, the bottom of the slab could be the ideal side for most testing.
6.3.11. Ensure there is no more than a I-mm departure in any of the areas to be tested by the DFT that is not related to mixture surface texture.
6.3.12. The slab should be stored on a rigid plate such as an approximately 25-mm (I -in.) thick piece of plywood to protect against defbrmation. Do not stack slabs or place the slab on a non-flat surface.
6.4. Sample Polishing Procedure’:
6.4.1. Before starting the polishing procedure of the prepared specimen, check that the condition of the TWPD meets the criteria set in Section 5.9. Gently clean any contamination from the tires, if necessary.
6.4.4. Gently lower the polishing tire carriage onto the specimen.
6.4.5. Close the safety door of’ the polisher.
6.4.6. Set the Automatic Counter to the desired number of revolutions established by the agency. Turn on the water flow. Begin polishing. One revolution of the polishing carriage corresponds to one pass made by all three wheels.
Note 5 —100,000 revolutions have been found to be sufficient to polish most compacted asphalt mixes to the terminal friction value, intermittent friction values may be obtained, if desired, to capture the rate of polishing of the asphalt mixture before it reaches its terminal friction value.
6.4.7. Once the sample has been polished, turn off the water flow, raise the polishing tire carriage, and slide out the test specimen slab.
6.5. Measure the friction value by the DFT according to ASTM E19l 1 in the same friction measurement path used to obtain the initial friction value.AASHTO PP 104 pdf download.