1、Standard Practice for Emulsified Asphalt Content of Cold Recycled Mixture Designs AASHTO Designation: PP 86-171Technical Section: 2a, Emulsified Asphalts Release: Group 3 (August 2017) American Association of State Highway and Transportation Officials 444 North Capitol Street N.W., Suite 249 Washing
2、ton, D.C. 20001 TS-2a PP 86-1 AASHTO Standard Practice for Emulsified Asphalt Content of Cold Recycled Mixture Designs AASHTO Designation: PP 86-171Technical Section: 2a, Emulsified Asphalts Release: Group 3 (August 2017) 1. SCOPE 1.1. This standard for mix design evaluation is used to determine the
3、 amount and composition of emulsified asphalt and other additives when using cold recycling (CR) of asphalt mixtures which includes cold in-place recycling (CIR) or cold central plant recycling (CCPR). The mix design is based on strength and other performance properties. 2. REFERENCED DOCUMENTS 2.1.
4、 AASHTO Standards: M 85, Portland Cement M 216, Lime for Soil Stabilization MP 31, Materials for Cold Recycled Mixtures with Emulsified Asphalt T 2, Sampling of Aggregates T 11, Materials Finer Than 75-m (No. 200) Sieve in Mineral Aggregates by Washing T 27, Sieve Analysis of Fine and Coarse Aggrega
5、tes T 30, Mechanical Analysis of Extracted Aggregate T 164, Quantitative Extraction of Asphalt Binder from Hot Mix Asphalt (HMA) T 166, Bulk Specific Gravity (Gmb) of Compacted Hot Mix Asphalt (HMA) Using Saturated Surface-Dry Specimens T 168, Sampling of Bituminous Paving Mixtures T 209, Theoretica
6、l Maximum Specific Gravity (Gmm) and Density of Hot Mix Asphalt (HMA) T 245, Resistance to Plastic Flow of Asphalt Mixtures Using Marshall Apparatus T 269, Percent Air Voids in Compacted Dense and Open Asphalt Mixtures T 283, Resistance of Compacted Asphalt Mixtures to Moisture-Induced Damage T 308,
7、 Determining the Asphalt Binder Content of Hot Mix Asphalt (HMA) by the Ignition Method T 312, Preparing and Determining the Density of Hot Mix Asphalt (HMA) Specimens by Means of the Superpave Gyratory Compactor T 331, Bulk Specific Gravity (Gmb) and Density of Compacted Hot Mix Asphalt (HMA) Using
8、 Automatic Vacuum Sealing Method 2017 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law.TS-2a PP 86-2 AASHTO 2.2. ASTM Standards: D3549, Standard Test Method for Thickness or Height of Compacted Bituminous Pav
9、ing Mixture Specimens D7196, Standard Test Method for Raveling Test of Cold Mixed Emulsified Asphalt Samples 2.3. Other Documents: LTPP Seasonal Asphalt Concrete Pavement Temperature Models, LTPPBind 3.1 Basic Asphalt Recycling Manual, Asphalt Recycling and Reclaiming Association and FHWA-HIF-14-001
10、, Annapolis, MD. 3. TERMINOLOGY 3.1. cold central-plant recycling (CCPR)the process in which the asphalt recycling takes place at a central location using a stationary cold mix plant. The resulting pavement serves as a base layer overlaid with a surface treatment or asphalt mixture overlay. 3.2. col
11、d in-place recycling (CIR)the on-site recycling process to a typical treatment depth of 75-100 mm (3-4 in.), using a train of equipment (tanker trucks, milling machines, crushing and screening units, mixers, pavers, and rollers) and an emulsified asphalt with or without a combination of additives (l
12、ime, cement, aggregate), generating and re-using 100 percent of the milled material, with the resulting pavement serving as a base layer overlaid with a surface treatment or asphalt mixture overlay. 3.3. reclaimed asphalt pavement (RAP)removed and/or processed pavement materials containing asphalt b
13、inder and aggregate. 4. SIGNIFICANCE AND USE 4.1. The procedure described in this standard is used to produce CIR or CCPR that satisfies mix design requirements. 4.2. Specifying an emulsified asphalt alone for CIR or CCPR may not be satisfactory in producing a good-performing mixture. The mix design
14、 described in this standard practice has been used successfully in many projects. 5. OBTAINING AND PREPARATION OF MATERIALS 5.1. Sampling Existing Pavement for CIR and CCPR: 5.1.1. Obtain cores from the areas to be recycled. The material provided must be representative of the material to be recycled
15、. Where visual differences in the pavement surface are noted or where construction or maintenance records indicate differences, obtain additional cores to evaluate the difference. If these additional cores show significant material differences, perform a separate mix design for each identified pavem
16、ent segment. Note 1Take cores using a pattern that results in a representative sample of the pavement to be recycled including at or near lane lines, within and between wheel paths, at the pavement edge and within shoulders if shoulders are to be recycled. Provide at least 180 kg (400 lb) of RAP per
17、 design, more if asphalt content or binder properties or recovered aggregate gradation analysis of the RAP are desired. 2017 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law.TS-2a PP 86-3 AASHTO 5.1.2. Crush
18、cores at ambient temperature or colder to obtain materials for the mix design. Note 2A jaw crusher, laboratory milling machine, or other suitable method is recommended for modeling the particle shape and gradation expected during recycling. 5.1.3. As an alternative to obtaining and crushing cores, o
19、btain RAP by milling. Mill the pavement from areas to be recycled to the specified depth. Note 3Consider a cold planer if the pavement section is uniform and a representative section is milled. Obtain samples provided the cold planer (milling machine) produces sufficient coarse material to conduct a
20、 mix design. Fine millings may not be acceptable if they are not coarse enough to represent the construction-produced millings. Only millings that represent the pavement to be recycled shall be collected. If the existing pavement surface is planned to be milled and removed during construction, the p
21、avement shall be milled in a similar manner and removed prior to milling for sampling purposes. Milling and sampling shall only be to the planned recycle depth. The material may be taken from one test location for each mix design to be performed. For example, if a pavement change exists within the l
22、imits of the roadway, one test location should be designated separating each area. 5.2. Sampling Existing Stockpiles for CCPR: 5.2.1. Remove the crust of the stockpile in accordance with T 168 and then sample the RAP in accordance with T 2. 5.2.2. Provide at least 180 kg (400 lb) of RAP per design,
23、and obtain more if asphalt content, binder properties, or recovered aggregate gradation analysis of the RAP are desired. 5.3. Processing of Recycled Asphalt Pavement (RAP) Materials: 5.3.1. Sieve the RAP according to T 27, with the exception that drying the RAP to constant mass shall be performed at
24、 40 2C (104 4F). If a significant amount of fine uncoated particles are present, perform washed sieve analysis on a representative sample in accordance with T 11. Process RAP materials to model the gradation expected during recycling. As an alternative, combine RAP materials to meet two of the grada
25、tion bands in MP 31. Note 4Adjustment of the gradation bands to local conditions and construction equipment is recommended. The selected gradations shall be chosen to match the expected field gradation as closely as possible, with the exception that a greater top size on the project is expected. Gra
26、dations on a project will vary from sample to sample. Slight adjustments in the field to the design emulsified asphalt content are often necessary to obtain optimum mixture performance. Performing the mix design at two gradations can determine an acceptable range of emulsified asphalt contents for t
27、he project. Ensure all materials pass the 25-mm (1-in.) sieve for 100-mm (4-in.) diameter specimens. 5.3.2. Obtain two representative samples of processed RAP for T 308 or T 164 testing for Section 6. 6. DETERMINE ASPHALT CONTENT AND GRADATION OF EXTRACTED AGGREGATE FROM RAP 6.1. Perform either T 30
28、8 or T 164 on two representative samples set aside from Section 5.3.2. 6.2. Determine the average asphalt content according to whichever method was used in 6.1. Note 5It is not possible to accurately determine an asphalt content and/or aggregate correction factor for RAP materials. One may be applie
29、d if the correction factor of the original RAP materials is known or can be based on experience with local aggregate materials. 2017 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law.TS-2a PP 86-4 AASHTO 6.3.
30、Sieve the extracted aggregate and determine the gradation according to T 30. Note 6Consider corrective aggregate meeting agency requirements if the amount passing the 4.75-mm (No. 4) sieve in the extracted mineral aggregate gradation is greater than 65 percent or if the asphalt content is greater th
31、an 5.5 percent, or both. Lab-prepared cold recycle mixture properties may also indicate the need for corrective aggregate in lieu of the T 308 and T 30 test results, such as low voids, low dry strength, or low retained strength. 7. EMULSIFIED ASPHALT AND ADDITIVES FOR MIX DESIGN 7.1. Select an emuls
32、ified asphalt in accordance with MP 31: 7.1.1. Obtain 7.6 L (2 gal) of the emulsified asphalt that will be used to produce the cold recycled mixture. Include the name and location of the supplier in the mix design report. Include the grade and properties of the emulsified asphalt in the mix design r
33、eport. 7.2. Samples of Other Additives: 7.2.1. Obtain 2.3 kg (5 lb) of quicklime, hydrated lime, or cement if needed for the mix design. Note 7Dry additives are sometimes used to improve early cohesion, strength, and moisture resistance. To limit brittle behavior, the quantity of cement is normally
34、limited to one-third the quantity of new residual asphalt from the emulsified asphalt and the quantity of lime should be limited to a maximum of 1.5 percent. 7.2.2. Obtain a sufficient amount of other additives (i.e., add stone) that will be used to complete the mix design. List the name and source
35、of all additives in the mix design report. 8. DETERMINATION OF STRENGTH OR STABILITY AND STRENGTH RATIO 8.1. Batching RAP Material: 8.1.1. Select a minimum of three emulsified asphalt contents in 0.5 percent to 1.0 percent increments covering a range typically between 1 percent and 4.0 percent by dr
36、y weight of RAP. Batch RAP material for each specimen conforming to the gradation expected in the field or to at least two of the three gradation bands shown in MP 31. Batch aggregate at the appropriate percentage, if required. Prepare six specimens for each emulsified asphalt content selected. As a
37、n option, additional specimens may be batched, compacted, and tested that have varying percentages of other additives such as quicklime. 8.1.1.1. For indirect tensile strength testing from T 283, determine the amount of RAP material required to produce a 150 mm (6 in.) diameter and 95 5 mm (3.75 0.2
38、 in.) tall specimen when compacted in the gyratory compactor at 30 gyrations. For Marshall stability testing from T 245, determine the amount of RAP material required to produce a 100-mm (4-in.) diameter and 63.5- 3-mm (2.5- 0.1-in.) tall specimen. Exclude plus 25-mm (1-in.) material from 100-mm (4-
39、in.) specimens. Note 8Compact to 30 gyrations if using gyratory compaction. Compact at 75 blows per side if using the Marshall compaction apparatus. Note 9Choose only one strength or stability test. 8.2. Preparing Lime Slurry: 2017 by the American Association of State Highway and Transportation Offi
40、cials. All rights reserved. Duplication is a violation of applicable law.TS-2a PP 86-5 AASHTO 8.2.1. Prepare slurry by adding the required quantity of additive to water using the ratio expected for the project. 8.2.2. Minimize the amount of additive lost in the form of dust. 8.2.3. Stir until thorou
41、ghly mixed, and continuously mix the slurry until it is used to prevent settling. 8.2.4. Cover to reduce water evaporation. 8.3. Mechanical Mixing: 8.3.1. Mix samples for testing using a mechanical bucket mixer or laboratory-sized pugmill. Add moisture that is expected to be added at the milling hea
42、d, typically 1.5 to 2.5 percent, and mix thoroughly. If any dry additives are in the mixture, add the additives to the dry RAP and mix thoroughly before adding the water. If slurry is used, add at the desired solids content by weight of dry RAP and mix thoroughly. 8.3.2. Mix RAP conditioned at room
43、temperature between 20 and 25C (68 and 77 F), thoroughly mix RAP with water, additives and water, or slurry then mix with emulsified asphalt at the expected delivery temperature. One specimen will be mixed at a time. Mixing time with emulsified asphalt should not exceed 60 s. Note 10RAP conditioned
44、at temperatures higher than 25C (77F) can be mixed and compacted to better simulate hot-weather field conditions. If ambient air temperatures are expected to be 29C (85F) or greater, then condition RAP and mold to 40C (104F) for compaction. Higher-temperature conditioning will likely have the effect
45、 of lowering the design emulsified asphalt content. If construction conditions are cooler, the field emulsified asphalt content demand could increase; however, it is impractical to mix and compact the RAP at cool temperatures in the laboratory. Note 11Before mixing the design samples, prepare trial
46、blends with expected moisture, additives and add stone, if any, to determine that the emulsified asphalt disperses throughout the blend. If an improvement is needed, adjust moisture content, going no higher than 3 percent. If an improvement is still needed, an emulsified asphalt formula change may b
47、e needed. 8.4. Compacting: 8.4.1. Immediately after mixing, compact the specimens. Compact the specimens at 25 2C (77 4F) (see Note 10 for higher-temperature conditioning). 8.4.2. Compact the specimens according to T 312 compaction procedures with the exception that the materials and the molds are n
48、ot heated unless desired as described in Note 10. 8.4.3. Compact six specimens at each emulsified asphalt content for strength or stability testing; three for unconditioned (dry) strength on cured samples and three for conditioned strength on cured samples for moisture conditioning. 8.5. Curing: 8.5
49、.1. Extrude the specimens from the molds after compaction. Handle specimens carefully as to not disturb or damage. Carefully remove the paper disks from the top and bottom of the specimens. 8.5.2. Place specimens in 60 1C (140 2F) forced draft oven with ventilation on sides and top. Place each specimen in a small container to account for material loss from the specimens. Cure compacted specimens at 60 1C (140 2F) to constant mass but do not heat for more than 48 h and not less than 16 h. Co
