1、Standard Specification for Determination of Optimum Asphalt Content of Cold Recycled Mixture with Foamed Asphalt AASHTO Designation: PP 94-18Technical Section: 2d, Bituminous Materials Release: Group 3 (August) American Association of State Highway and Transportation Officials 444 North Capitol Stre
2、et N.W., Suite 249 Washington, D.C. 20001 TS-2d PP 94-1 AASHTO Standard Practice for Determination of Optimum Asphalt Content of Cold Recycled Mixture with Foamed Asphalt AASHTO Designation: PP 94-18 Technical Section: 2d, Bituminous Materials Release: Group 3 (August) 1. SCOPE 1.1. This standard pr
3、actice for cold recycling mix design is used to determine the amount of foamed asphalt, water, and other additives when using cold recycling (CR) of asphalt pavements, which includes cold in-place recycling (CIR) or cold central plant recycling (CCPR). The mix design is based on the strength propert
4、ies of cold recycled mixture. 1.2. The values stated in SI units are to be regarded as the standard. 1.3. This standard practice may involve hazardous materials, operations, and equipment. This standard practice does not purport to address all of the safety concerns, if any, associated with its use.
5、 It is the responsibility of the user of this procedure to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. 2. REFERENCED DOCUMENTS 2.1. AASHTO Standards: MP 38, Mix Design of Cold Recycled Mixture with Foamed Asphalt R 90, Sam
6、pling Aggregate Products T 11, Materials Finer Than 75-m (No. 200) Sieve in Mineral Aggregates by Washing T 27, Sieve Analysis of Fine and Coarse Aggregates T 30, Mechanical Analysis of Extracted Aggregate T 164, Quantitative Extraction of Asphalt Binder from Hot Mix Asphalt (HMA) T 168, Sampling of
7、 Bituminous Paving Mixtures T 180, Moisture-Density Relations of Soils Using a 4.54-kg Rammer and a 457-mm Drop T 245, Resistance to Plastic Flow of Bituminous Mixtures Using Marshall Apparatus T 283, Resistance of Compacted Hot Mix Asphalt (HMA) to Moisture-Induced Damage T 308, Determining the Asp
8、halt Binder Content of Asphalt Mixtures by the Ignition Method T 312, Preparing and Determining the Density of Hot Mix Asphalt (HMA) Specimens by Means of the Superpave Gyratory Compactor 2.2. Other References: LTPP Seasonal Asphalt Concrete Pavement Temperature Models, LTPPBind 3.1 Basic Asphalt Re
9、cycling Manual, Asphalt Recycling and Reclaiming Association and FHWA-HIF-14-001, Annapolis, MD, 2014. 2018 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law.TS-2d PP 94-2 AASHTO Wirtgen Cold Recycling Technol
10、ogy, Wirtgen GmbH, Windhagen, Germany, 2012. 3. TERMINOLOGY 3.1. reclaimed asphalt pavement (RAP)removed and/or processed pavement materials containing asphalt binder and aggregate. 3.2. cold in-place recycling (CIR)the on-site recycling process in which the existing asphalt pavement is recycled usi
11、ng a specialized train equipment (tanker trucks, cold planing machines, crushing/screening or sizing units, mixers, pavers, and compaction rollers). The CIR process uses 100 percent of the on-site generated RAP, and a foamed asphalt with or without a combination of additives (e.g., lime, cement, and
12、 aggregate) to produce CIR mixture, and typically treats an asphalt pavement with a depth of 75 to 100 mm (3 to 4 in.). The CIR mixture is used as a base layer overlaid with a surface treatment or asphalt overlay. 3.3. cold central-plant recycling (CCPR)the process in which the asphalt recycling tak
13、es place at a central location using a stationary cold mix plant. The stationary plant could be a specifically designed plant or a CIR train minus the cold planing machine set up in a stationary configuration. The CCPR mixture is used as a base layer overlaid with a surface treatment or asphalt over
14、lay. 4. SUMMARY OF THE PRACTICE 4.1. Material SelectionThe provided in-place RAP must be representative of the materials to be recycled. The RAP, asphalt binder, additional aggregate, and other additives are selected that meet the environmental and traffic requirements applicable to the paving proje
15、ct. 4.2. Design Mixing Water Content SelectionReplicate RAP specimens are compacted using the modified proctor test method with at least three trial mixing water contents. The mixing water content corresponding to the maximum dry density of RAP specimen is selected as the design mixing water content
16、. 4.3. Design Foamed Asphalt Content SelectionReplicate cold recycled mixture specimens are compacted in the Superpave gyratory compactor at 30 gyrations or in the Marshall compaction apparatus at 75 blows per side with at least three trial foamed asphalt contents. The design binder content is selec
17、ted on the basis of satisfactory conformance with the requirements of MP 38. 5. SIGNIFICANCE AND USE 5.1. This practice outlines standard procedures for determining optimum water content and optimum asphalt content of cold recycled mixture with foamed asphalt. Its purpose is to produce CIR or CCPR a
18、sphalt mixture that satisfies mix design requirements. 6. OBTAINING AND PREPARATION OF MATERIALS 6.1. Sampling Existing Pavement for CIR and CCPR: 6.1.1. Obtain cores from the areas to be recycled. The material provided must be representative of the material to be recycled. Where visual differences
19、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 pavement segment. 2018 by the Am
20、erican Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law.TS-2d PP 94-3 AASHTO 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 an
21、d between wheel paths, at the pavement edge, and within shoulders if shoulders are to be recycled. Provide at least 180 kg (400 lbs) of RAP per design, or more if asphalt content or binder properties or recovered aggregate gradation analysis of the RAP are desired. 6.1.2. Crush cores at ambient temp
22、erature 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. 6.1.3. As an alternative to obtaining and crushing cores, obtain RAP by milling.
23、 Mill the pavement from areas to be recycled to the specified depth. Note 3Consider using a cold planer (milling machine) to obtain a RAP sample if the pavement section is uniform and a representative section can be milled. If the existing pavement changes within the limits of the project, obtain se
24、parate samples for each area and prepare separate mix designs for each sample. 6.2. Sampling Existing Stockpiles for CCPR: 6.2.1. Remove the crust of the stockpile in accordance with T 168 and then sample the RAP in accordance with R 90. 6.2.2. Obtain at least 180 kg (400 lbs) of RAP per design, and
25、 obtain at least 14 kg (30 lbs) more if asphalt content, recovered binder properties, or aggregate properties of the RAP are desired. 6.3. Processing of Recycled Asphalt Pavement (RAP) Materials: 6.3.1. Conduct a sieve analysis in accordance with T 27 on a representative sample of the RAP, with the
26、exception that drying the RAP to a constant mass shall be performed at 40 2C (104 4F). If a significant amount of fine uncoated particles are present, perform a washed sieve analysis on a representative sample in accordance with T 11. 6.3.2. Process RAP materials to model the gradation expected duri
27、ng recycling. The produced RAP gradation shall fall within the gradation band suggested in MP 38. 6.3.3. Obtain two representative samples of processed RAP for T 164 or T 308 testing for Section 7. 7. DETERMINATION OF ASPHALT CONTENT AND GRADATION OF EXTRACTED AGGREGATE FROM RAP 7.1. Perform T 164 o
28、r T 308 on two representative samples set aside from Section 6.3.3. 7.2. Determine the average asphalt content according to T 164 or T 308. Note 4It is not possible to determine an asphalt content and/or aggregate correction factor for RAP materials. One may be applied if the correction factor of th
29、e original RAP materials is known or can be based on experience with local aggregate materials. 7.3. Sieve the extracted aggregate and determine the gradation according to T 30. Note 5Consider adding aggregate meeting agency requirements if the amount passing the 4.75-mm (No. 4) sieve in the extract
30、ed mineral aggregate gradation is greater than 65 percent or if the asphalt content is greater than 5.5 percent, or both. Lab-prepared cold recycle mixture properties may also indicate the need for corrective aggregate in lieu of the T 30 and T164 or T 308 test 2018 by the American Association of St
31、ate Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law.TS-2d PP 94-4 AASHTO results, such as low voids, low dry strength, or low retained strength. For CCPR material, the percentage of additional aggregate used in the mixture shall not exceed 50 p
32、ercent. 8. DETERMINATION OPTIMUM WATER CONTENT FOR RAP 8.1. Dry the RAP materials to a constant mass at an ambient temperature. Note 6Constant mass is defined as no more than 0.05 percent change in mass in 2 hours. If 19-mm (3/4in.) diameter molds are used for compaction, remove particles above 19-m
33、m (3/4in.) sieve. A fan is typically used for drying RAP. 8.2. Determine the optimum water content of a representative sample of the dried RAP in accordance with T 180. Note 7Designers use their experience with the materials to determine trial water contents (typically 2-6 percent) for mixing with R
34、AP materials. The recommended interval for the trial water contents is 1 percent. Add water slowly into RAP and use a scoop for mixing until uniform. Note 8Water may be squeezed out at bottom of the mold during compaction. Any water left in the compactor needs to be cleaned after compaction. 9. SELE
35、CTION OF RECYCLING AGENT 9.1. Select an asphalt binder for foaming in accordance with MP 38. 9.1.1. Obtain 7.6 L (2 gal) of asphalt that will be used to produce foamed asphalt binder. Include the name and location of the supplier in the mix design report. Include the grade and properties of the asph
36、alt binder in the mix design report. 9.2. Determine the optimum water content for foamed asphalt binder in accordance with Wirtgen GmbH (2012). 9.2.1. Heat the asphalt binder in laboratory foaming unit until the required temperature is achieved. Maintain the required temperature for at least 5 minut
37、es prior to fabricating foamed asphalt binder. 9.2.2. Select a minimum of three injected water contents in 0.5 percent to 1.0 percent increments covering a range typically between 2.0 percent and 4.0 percent by weight of asphalt binder. 9.2.3. Determine the expansion ratio and half-life of foamed as
38、phalt binder for each injected water content according to Wirtgen GmbH (2012). To ensure a good workability of cold recycled mixture, the expansion ratio and half-life of foamed asphalt binder shall meet the minimum requirements specified in Table 1. Table 1Minimum Requirements of Foamed Asphalt Pro
39、perties Aggregate Temperature 10nullC to 15nullC (50-59F) Greater than 15nullC (59F) Expansion Ratio (times) 10 8 Half-life (seconds) 8 6 9.2.4. Choose the optimum water content as an average of the two water contents that meets the minimum requirements of foamed asphalt properties. 9.2.5. Repeat st
40、eps 9.2.1 to 9.2.4 to determine the minimum required temperature of asphalt binder for foaming. 2018 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law.TS-2d PP 94-5 AASHTO Note 9The required heating temperatur
41、e is in the range of 160 to 190C, which normally starts at 160C. A higher heating temperature usually creates better foam, but meanwhile accelerates the aging of binder. Thus, the minimum required heating temperature is recommended for fabricating foamed asphalt binder. The Wirtgen WILB 10S has been
42、 shown to be suitable laboratory foaming unit that can produce acceptable foamed asphalt binder. Other foaming units may be used. 9.3. Select other additives in accordance with MP XX. 9.3.1. Obtain 2.3 kg (5 lbs) of hydrated lime or cement if needed for the mix design. Note 10Mineral additives are o
43、ften used to improve strength, rutting resistance and moisture resistance. The added lime content is typically at 1-1.5 percent by dry weight of RAP. To prevent brittle behavior of the mixture, the added cement content should be typically kept between 0.25-1 percent by weight of RAP. The ratio of ce
44、ment content to asphalt content should be a maximum of 1:2.5. 9.3.2. Obtain a sufficient amount of other additives that will be used to complete the mix design. List the name and source of all additives in the mix design report. 10. DETERMINATION OF STRENGTH AND STRENGTH RATIO 10.1. Batching RAP Mat
45、erial: 10.1.1. Select a minimum of three foamed asphalt contents in 0.5 percent to 1.0 percent increments covering a range typically between 1.0 percent and 4.0 percent by dry weight of RAP. Batch RAP material for each specimen conforming to the gradation expected in the field. Batch virgin aggregat
46、e, if needed, at the appropriate percentage. Prepare six specimens for each foamed asphalt content selected. As an option, additional specimens may be batched, compacted, and tested that have varying percentages of other additives such as cement or hydrated lime. 10.1.1.1. For indirect tensile stren
47、gth testing following T 283, determine the amount of RAP material required to produce a 150-mm (6-in.) diameter and 95 2.5-mm (3.75 0.1-in.) tall specimen or a 100-mm (4-in.) diameter and 63.5 1.5-mm (2.5 0.06-in.) tall specimen when compacted in the gyratory compactor at 30 gyrations, or a 100-mm d
48、iameter and 63.5 1.5-mm (2.5 0.06-in.) tall specimen when compacted in the Marshall compaction apparatus at 75 blows per side. 10.2. Mixing RAP with a Mineral Additive: 10.2.1. Add the desired amount of additive to the RAP and mix until uniform. 10.2.2. Minimize the loss of dry mineral additives by
49、using a cover during mixing. Note 11If lime slurry is used, it needs to be prepared at the desired solids content by weight of dry RAP and mix thoroughly with water. Stir slurry until thoroughly mixed, and continuously mix the slurry until it is used to prevent settling. 10.3. Mixing RAP with Water and Foamed Asphalt 10.3.1. Mix samples for testing using a mechanical bucket mixer, a laboratory mixer or laboratory-sized pugmill. Add water that is expected to be 100 percent optimum water content determined in Secti
