The National Academies

NCHRP Synthesis 20-05/Topic 51-08 [Active (Synthesis)]

Practice and Performance of Cold In-Place Recycling and Cold Central Plant Recycling
[ NCHRP 20-05 (Synthesis of Information Related to Highway Practices) ]

  Project Data
Funds: $45,000
Authorization to Begin Work: 5/1/2019 -- estimated
Staff Responsibility: Tanya Zwahlen
Research Agency: Gardiner Technical Service LLC
Principal Investigator: Mary Stroup-Gardiner
Effective Date: 9/16/2019
Fiscal Year: 2019

Final Scope

Cold recycling consists of recycling reclaimed asphalt pavement (RAP) without the use of heat. The two categories of cold recycling that are becoming more prevalent in the road building industry include: Cold In-place Recycling (CIR) and Cold Central Plant Recycling (CCPR). A typical layer thickness is three to five inches. CIR occurs in situ where a portion of the upper layers of existing asphalt pavement is milled, crushed, blended with recycling agents and repaved while leaving the lower existing pavement in place. The CIR process occurs in the roadway without the RAP material leaving the road. The CCPR process produces a product that is similar to CIR but the recycling occurs at a mobile plant. The RAP used for CCPR may either come directly from a paving project by milling or be found in existing RAP stockpiles. Typical recycling agents used for CIR and CCPR are emulsified asphalt or foamed asphalt.

The objective of this synthesis is to document how CIR and CCPR technologies are selected, designed, constructed, and evaluated by state DOTs.

Information to be gathered will include, but not be limited to:
• DOT history and experience with CIR and CCPR as part of rehabilitation strategies (e.g. number of projects and tons or lanes miles per year, type of roads used, equipment used)
• Selection criteria for recycling projects (e.g. pavement condition, amount of crack sealer in pavement, maintenance of traffic, funding)
• Characterization of RAP (e.g. amount of deterioration, age of material, extracted binder)
• Specifications used (e.g. mixture design, pay items, construction and acceptance requirements and evaluation methods, how soon traffic resumes, requirements prior to traffic resuming)
• Criteria for selecting binding agent, rejuvenator, stabilizing agent (e.g. emulsion or foamed asphalt, cement, lime)
• Structural design inputs and criteria (e.g. whether or not chip seal is recycled, minimum and maximum layer thickness)
• Surface treatments over CIR or CCPR (e.g. asphalt overlay, chip seal, double chip seal)
• Cost comparison to conventional HMA treatments
• Barriers for adoption of CIR or CCPR
• Recurring issues and solutions
• Performance data on pavement management system level and/or project-based level

Information will be gathered through a literature review, a survey of state DOTs and interviews. Based on the results of the survey, at least five DOTs and one local agency will be selected for case examples. The case examples will represent both CIR and CCPR projects, different climatic regions, and the level of agency experience with either CIR or CCPR.

Information Sources:
• Stroup-Gardiner, Mary. NCHRP Synthesis 421: Recycling and Reclamation of Asphalt Pavements Using In-Place Methods. Synthesis 421, National Cooperative Highway Research Program, Washington, DC, 2011.
• Asphalt Recycling and Reclaiming Association. Basic Asphalt Recycling Manual, 2nd Ed. Annapolis, MD, 2015.
• Schwartz, Charles, Brian Diefenderfer, and Benjamin Bowers. Material Properties of Cold In-Place Recycled and Full-Depth Reclamation Asphalt Concrete. Report 863, National Cooperative Highway Research Program, Washington, DC, 2017.
• Federal Highway Administration. Overview of Project Selection Guidelines for Cold In-place and Cold Central Plant Pavement Recycling, Publication FHWA-HIF-17-042, Washington, DC, August 2017.
• Ma, Wagyu, Randy West, Nam Tran, Brian Diefenderfer, and C. Chen “Effects of Mineral Additives on Cold Recycled Foamed Asphalt Mixtures in Laboratory- and Field-Curing Conditions.” Accepted for Publication to Transportation Research Record, 2018.
• NCHRP Project 09-62, Rapid Tests and Specifications for Construction of Asphalt-Treated Cold Recycled Pavements.

Topic Panel

Howard J. Anderson, Utah DOT
Edith Arambula Mercado, Texas A&M Transportation Institute
Bomasur Banzon, California DOT
Sheila L. Hines, Nova Engineering
Timothy Kelley, Maine DOT
Hong J. Park, Tennessee DOT
Eyoab Zegeye Teshale, Minnesota DOT
Morgan Kessler, Federal Highway Administration
Nelson H. Gibson, Transportation Research Board
TRB Staff 
Tanya M. Zwahlen
First Panel: September 16, 2019
Teleconference with Consultant: TBD
Second Panel: June 16, 2020





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