AASHTO PP 91-18 pdf free download

AASHTO PP 91-18 pdf free download.Emulsified Asphalt Scrub Seal Design.
3. TERMINOL .OGY 3.1. Definitions: 3.1.1. average least dimension- reduction of median particle size to account for flat particles by using flakiness index. Represents the sealcoat thickness in the wheel path where traffic forces flat aggregate to orient on its flattest side. 3.1.2. badly pocked, porous, oxidized- severe raveling of surface with much cracking. 3.1.3. flushed-bleeding- free asphalt on the pavement surface with little or no texture. 3.1.4. median particle size- -theoretical aggregate size that corresponds to 50 percent passing on the gradation curve. 3.1.5. medium cracking- -medium severity transverse, longitudinal, and/or longitudinal joint cracking. Spalling is observed at the crack edge and some cracks have begun to become interconnected. Block cracking, with cracks creating sections approximately 1 to 3 ft in width, also falls under this distress category. 3.1.6. severe cracking- -high severity transverse, longitudinal, and/or longitudinal joint cracking. There is significant spalling at crack edges and cracks have become interconnected. Alligator cracking is also included in this distress category. Use caution in applying maintenance treatments on pavements with severe cracking distress. 3.1.7. slight cracking- -single or well-spaced low severity transverse or longitudinal cracks. Also includes low severity longitudinal joint cracking. 3.1.8. slightly pocked, porous, oxidized- -raveling beginning to show with moderate cracking.3.1.9. smooth, non-porous- -some free asphalt on the pavement surface, but with some cracking. 4. SIGNIFICANCE AND USE 4.1. This standard practice may be used to determine the quantities of materials required for the construction of emulsified asphalt scrub seals. Practitioners may select one of the two design methods detailed in this practice. 4.2. The design practice is similar to those used for chip seals with adjustments made to account for the surface condition and cracking of the existing pavement. 5. SCRUB SEAL DESIGN REQUIREMENTS 5.1. Materials: 5.1.1. Scrub Seal- Emulsified asphalt and aggregate used in the design shall meet the requirements specified by the Owner Agency and shall be representative of the materials used for the project. 5.1.2. Fog Seal (Optional)- Common emulsified asphalt grades for fog seal include CSS-1, CSS-1h, SS-1, SS-1h, and CQS- 1h. Materials shall meet the requirements ofM 140, M 208, orM 316. Other materials and specifications may be used at the request of the Owner Agency. For fog seal, the emulsified asphalt is usually diluted at a 1:1 ratio with potable water. 5.2. Design Methods for Selection of Initial Emulsion and Aggregate Application Rates: 5.2.1. All design work will be carried out using aggregate either directly from the job site stockpile or equivalent material from the same source and having substantially the same material properties. 5.2.2. Modified Kirby Design Method: 5.2.2.1. Aggregate Application Rate: 5.2.2.1.1. Fabricate a board measuring 3 ft by 1’/2 ft. A 3/4-in. thick particle board works well for this item. Attach 1 in. by 2 in. pine wood strips to the edge of the board to create a raised edge. 5.2.2.1.2. Weigh the completed board and record the weight in pounds. 5.2.2.1.3. Place the aggregate to be used on the project on the board. The quantity will vary depending on the gradation, shape, and crushed content of the aggregate, but should be no less than 5 lb and no greater than 25 Ib. Fit as many aggregate particles on the board within the confines of the edging as possible. The aggregate particles should not overlap each other and should be only one stone thick. AASHTO PP 91-18 pdf download.