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Pavements

Recycled Concrete Aggregate

Federal Highway Administration National Review Guide

Purpose

The purpose of this review is to capture for technical deployment the most advanced uses of recycled concrete aggregate (RCA) and then transfer the knowledge to all State Transportation Agencies (STA). Through this sharing of information, we intend to showcase how other STAs overcome barriers and advance the routine use of RCA. Specific uses or applications will be identified along with their barriers and benefits to implementation. Specifications, construction practices and implementation challenges will also be documented. This information will then be disseminated to all STAs through technical guidance, training, and guide specifications, as necessary.

Review Methodology

The RCA review will involve visiting several different states, meeting with state and industry personnel and some site visits. It is anticipated that the review will be completed in fiscal year 2003 with a final report published in 2004. The Recycled Concrete Aggregate (RCA) review team consists of FHWA, EPA, an AASHTO representative from the subcommittee on materials, and a representative of the American Concrete Institute technical committee on recycling (555).

The state visits will generally follow the same agenda. The Review Guide will be sent to the selected states 30 days before arrival. The local FHWA and STA representative will assist in arranging meetings and site visits.

Discussion Groups

Discussion groups will be used to gain knowledge about different activities and operations. Attached is a list of questions and issues that will be discussed at each discussion group. The following is a list of discussion groups and requested representation from the STA, FHWA, and other organizations:

  • Leadership - Director of Transportation, Division Administrator, State EPA Director, State Environmental Assistance Agency.
  • Planning & Environmental - Environmental Specialist and Planning Specialist, and State EPA/Environmental Assistance Agency.
  • Performance, Design, Materials and Research - Pavement Management Engineer, Maintenance Engineer, Materials Engineer, Pavement Design Engineer, Structural Engineer, Materials, Specification, and Research Engineer.
  • Project Administration (with first-hand experience using RCA) - Project Engineer, Prime Contractor, Aggregate Producer, Inspections Staff, and Laboratory Technicians.
  • Industry - Local Association of General Contractors (AGC) Chapter, American Concrete Pavement Association (ACPA), Asphalt Industry, Crushed Concrete Industry and Aggregate Industry.

Site Visits

Site visits will be used to gain further insight into the overall operation and performance of projects with RCA, if possible. State Review Coordinators should limit site visits only to those where the visit will add value to the review. The following are examples of sites that may be desirable to visit:

  • Previously constructed pavements & structures that utilized RCA.
  • Current construction projects that are using RCA.
  • Recycling facilities that process concrete rubble into RCA.
  • Ongoing experimental research project sites involving RCA.

Materials

We would like to obtain specific documents that are related to the STA's use of RCA. The following are examples of documents we would like to obtain:

  • Vision, mission and strategic plan
  • Environmental assessments & plans
  • Environmental permits
  • Pavement management performance data/curves
  • RCA usage trends
  • Design procedures
  • Specifications
  • Test Reports
  • Demonstration/Research reports

Conclusion

A closeout meeting will be held on the last day of the review for all interested and available parties. When the reports from all state reviews are completed and compiled into a draft final report, a copy of the draft report will be mailed to the FHWA and STA Coordinators for their review and comment.

Recycling Logo


Leadership

  1. What is your agency's vision regarding the use of recycled concrete aggregate (RCA)? What is the driving force behind this vision?

  2. What policies or practices have changed to support this vision? Do you foresee any changes in the next 5 years related to the use of RCA?

  3. Is recycling an integral part of your strategic plan, annual plan, or other?

  4. What is your agency's current policy regarding the use of RCA?

  5. What is your agency's role in promoting the use of RCA?

  6. What barriers have you overcome to increase the use of RCA?

  7. Does your agency have dedicated staff for the purpose of implementing recycling programs and technology? If so, how many, and where are they located in your organization?

Estimated Time: 90 minutes


Planning & Environmental

  1. How do you support the use of RCA (or recycled materials in general)?

  2. What barriers have you overcome to increase the use of recycled concrete as aggregate (RCA)?

  3. What barriers currently exist that prevent further use of RCA?

  4. Provide a brief description of various uses of RCA in your state and usage trends.

  5. Please describe your RCA quality requirements?

  6. Please describe any challenges that have occurred at processing facilities or sites using RCA? What corrective action was performed?

  7. Detail any major differences between site-specific or general procedures (i.e., sourcing,permits, specifications, approvals)for use of RCA and virgin aggregate material. Detail how these procedures and the associated information are coordinated within the department and other agencies.

  8. What further research, laboratory work, or policy initiatives would be necessary to advance the use of RCA.

  9. Provide details of any ongoing, completed or compiled research and demonstration projects regarding RCA.

  10. Describe any instances where the use of RCA was precluded in a project and the circumstances or basis of the decision.

  11. Specify any major differences between operating criteria (i.e.,permits, approvals, testing,dust control, surface water and wash water management, sediment controls, stockpile management)for processing or use of RCA and virgin aggregate material. Detail how these procedures and relevant information are coordinated within the department and other agencies.

  12. Does environmental documentation identify potential recycled materials that could be utilized on projects?

  13. Are there any restrictions that recognize the previous use of contaminated or borderline contaminated recycled materials that may be present in the RCA (example: flyash with high metal content)?

  14. What type of waste product is RCA defined as?

  15. Are there any statutes or regulations that pertain to the use of RCA?

  16. Do the statutes or regulations contain definitions concerning RCA?

  17. Is there a permitting process for the use of RCA?

  18. Are there any compliance evaluations performed on the use of RCA?

  19. Are there any special considerations for transporting RCA?

  20. Is disposal of RCA allowed in municipal solid waste landfills?

  21. Is there any air emission standards specifically designed for the use of RCA?

  22. What notification is required prior to destruction/construction activities associated with RCA?

  23. Are there requirements to assure that there is no adverse impact to ground water or surface waters?

  24. Describe the closure and post-closure monitoring and maintenance requirements applicable to construction activities with RCA.

Planning

  1. During the development of your long-range plan, do you consider the use of recycling as part of the seven broad planning factors identified in TEA-21 to be considered in the planning process (economic, environmental, or system preservation). If not, when?

  2. Is there an attempt to balance recyclable materials when identifying projects within the planning process?

  3. Do you see benefits in considering RCA in the planning process?

Estimated time: 3 hours


Performance, Design, Materials, & Research

General
  1. How do you support the use of RCA (or recycled materials in general)?

  2. What was the driving force to decide to recycle?

  3. What barriers have you overcome to increase the use of recycled concrete as aggregate (RCA)?

  4. What barriers currently exist that prevent further use of RCA?

  5. What further research, laboratory work, or policy initiatives would be necessary to assist you overcoming barriers?

  6. Provide a brief description of various use trends of RCA in your state.

  7. Please describe your RCA quality requirements?

  8. Please describe any problems that have occurred at processing facilities or sites using RCA? What corrective action was performed?

  9. When is the decision made about the use of RCA on a particular project?

  10. Who determines the pavement type selection?

  11. Does the STA consider the use of RCA in their reconstruction and/or rehabilitation pavement designs?

  12. When determining the pavement type selection and then the detailed design, is RCA considered in a life cycle cost analysis? If so, what dollar values are used for construction and residual cost?

  13. Are existing concrete sources, which are planned for removal and owned by the STA, reviewed to determine how the RCA could be used on future projects when removed? When does this occur?

  14. Does the STA consider abutting land uses and local drainage characteristics when considering the use of RCA as part of the pavement structure?

  15. Has anything in design limited the use of RCA in a project?

Pavement Thickness Design:
  1. In which pavement layers are RCA's allowed?

  2. What design process do you use (i.e., AASHTO or mechanistic design)?

  3. Are any adjustments made to structural coefficients, layer thicknesses, stiffness values or other parameters in the STA pavement design procedures because RCA is utilized?

  4. If RCA is utilized as a surface course, have skid characteristics been investigated? Is there an effect on the micro-texture, and is it acceptable?

  5. Does the method of construction and manufacturing of RCA impact the design of the pavement section?

Specifications
  1. What are the differences in requirements for virgin aggregates and RCA materials?

    1. Characterization (i.e., method, end-result)

    2. Physical properties

    3. Acceptance (i.e., percent within limits, incentive disincentive)

    4. Etc.

  2. Do the specifications provide enough latitude for contractors to bid RCA as an option? Explain answer and why.

  3. Has the STA ever offered an incentive or value engineering proposal for the use of RCA?

  4. Has alternate bidding been used with RCA?

  5. Are contractors provided the flexibility to make the decision to utilize RCA when the material meets standard specification requirements, or does the state require additional approvals and testing? What are the differences?

Materials
  1. Do you use source approval for the RCA? What is the acceptance criterion?

  2. Do you approve stockpiles of RCA for use? What is the acceptance criterion?

  3. Are the fines used in the new mixture? Are they stockpiled separately?

  4. How do you monitor the moisture of the coarse and fine aggregates?

  5. Have you performed any resilient modulus testing on materials with RCA incorporated?

  6. Do you ever reuse RCA that was known to have exhibited D cracking? Where?

  7. Have you ever reused RCA that was known to be alkali silica reactive? In what capacity was it used and how did it perform?

  8. Have you observed any changes in constructability as a result of the usage of RCA as compared to virgin aggregates?

  9. Do you perform a hardness test on the RCA? If so, which one? Are the results comparable to virgin aggregates?

Base/Subbase
  1. What type of aggregate durability test is performed on RCA? Are the results comparable to tests performed on virgin aggregates?

  2. Have you observed degradation in the gradation as a result of the use of RCA as compared to virgin aggregates?

Hot Mix Asphalt
  1. Is freeze thaw testing (ASTM C 666) performed on the original and the proposed RCA mix? What method of testing is used?

  2. What type of aggregate durability test is performed on RCA? Are the results comparable to tests performed on Virgin mixes?

  3. How does the use of RCA impact the asphalt demand of the mix.

  4. Have you investigated the impact of RCA on the HMA's stripping potential?

  5. Does the use of RCA impact the volumetric properties of the HMA mix?

  6. Have there been any issues during paving that have had an adverse effect on achieving placement, consolidation, and finishing of the RCA concrete?

Concrete
  1. Is a petrographic analysis (ASTM C 856) performed on the existing concrete to assess its potential use as a RCA?

  2. Is a petrographic analysis (ASTM C 856) performed on PCC samples that have incorporated RCA to determine its microstructure?

  3. Is freeze thaw testing (ASTM C 666) performed on the original and the proposed RCA mix? What method of testing is used?

  4. What air content and air void distribution (ASTM C 457) criteria are required for concrete made with RCA?

  5. Is D cracking reduced in RCA concrete compared to virgin concrete?

  6. What type of aggregate durability test is performed on RCA? Are the results comparable to tests performed on virgin mixes?

  7. Is the mortar bar test (ASTM C 1260 or ASTM C1293) performed on the RCA mixes?

  8. Do the locally available portland cements typically have high alkali contents?

  9. Is the total alkali content of a concrete mixture restricted in concrete made with virgin as well as RCA?

  10. If deicers have been utilized, are the NaCl and the equivalent alkali content (Na2O + .658K2O) determined for both the RCA fines and coarse particles? Are these tests done as a function of depth from the surface?

  11. What has your experience been with achieving a desired compressive or flexural strength for RCA mixes? Are you required to change the w/c ratio or admixtures as compared to virgin mixes?

  12. What moisture state is specified for the RCA aggregates during batching and mixing? Has control of uniform moisture been an issue?

  13. Have there been any observations on increased or decreased shrinkage for RCA concrete compared to virgin?

  14. Do RCA concretes have similar workability as conventional concrete?

  15. Have there been any issues during paving that have had an adverse effect on achieving placement, consolidation, and finishing of the RCA concrete?

  16. Have you performed any studies on aggregate interlock performance with RCA as compared to virgin aggregates?

  17. Are you aware of any environmental concerns, which have an effect on the materials properties of the RCA concrete?

Pavement Management
  1. Have you perform any FWD testing to measure resilient modulus on RCA projects?

  2. What are the typical resilient modulus values for RCA and virgin materials in similar situations?

  3. Are their any particular distresses observed or not observed on projects that have used RCA as compared to virgin materials? (Do you have data to support this and can I have a copy?)

  4. What is the typical form of distress that triggers rehabilitation or reconstruction of typical versus RCA pavement sections?

  5. Have you developed any performance curves for RCA? If yes, how do I obtain a copy?

Research
  1. Have you had any issues that have resulted into a research project?

  2. What demo or research projects have been performed?

Estimated time: 4 hours


Project Administration

  1. How do you support the use of RCA (or recycled materials in general)

  2. What barriers have you overcome to increase the use of recycled concrete as aggregate (RCA)?

  3. What barriers currently exist that prevent further use of RCA?

  4. What further research, laboratory work, or policy initiatives would be necessary to assist you overcoming barriers?

  5. Provide a brief description of various use trends of RCA in your state.

  6. Describe the different RCA operations you have experienced.

    1. What was the destruction process?

    2. What was the source of the material?

    3. What type of crushing operation was used (stockpiles and equipment)?

    4. Is there a specification that describes this process? Can we have a copy?

  7. If steel or rebar is present, how is this removed?

  8. What is your typical source of RCA (i.e., pavement, bridges, buildings)?

  9. Discuss the fines content of the recycled material. Does the material need to be cleaned prior to stockpiling?

  10. Are the fines restricted or limited in mixtures with RCA?

    1. Base

    2. Asphalt

    3. Concrete

  11. Please describe your feed system into concrete or HMA plants for RCA?

  12. Source approval for recycled material and other virgin material?

  13. What type of mixer is used, central mixer, truck mixer or portable mixer?

  14. What types of admixtures are typically used? Any special considerations with the recycled concrete?

  15. Does the use of pozzolans impact the use of RCA?

  16. Provide a brief description of various markets for RCA in your service area and recent production, usage and pricing trends.

  17. Provide details of any ongoing, completed or compiled research and demonstration projects regarding RCA.

  18. Describe any instances where the use of RCA was precluded in a project and the circumstances of the situation.

  19. Provide details on any problems that have occurred at your facility or a project site using RCA. Describe any corrective actions, monitoring and follow-up employed to address any problems or concerns.

  20. What quality assurance procedures are employed to monitor the process and product of RCA?

  21. Are there any construction issues different for RCA and virgin aggregates?

Estimated time: 2 hours


Industry

  1. How do you support the use of RCA (or recycled materials in general)?

  2. What barriers have you overcome to increase the use of recycled concrete as aggregate (RCA)? State and private work?

  3. What barriers currently exist that prevent further use of RCA?

  4. What further research, laboratory work, or policy initiatives would be necessary to assist you overcoming barriers?

  5. Provide a brief description of various use trends of RCA in your state.

  6. Please describe your RCA quality requirements.

  7. Please describe any problems that have occurred at processing facilities or sites using RCA. What corrective action was performed?

  8. What was the driving force to decide to recycle?

  9. What product is the most desirable: coarse or fines? What do you do with the excess?

  10. Are their any environmental policies, permits, or statutes that impact the way you process and handle RCA?

  11. Do STA specifications provide enough latitude for contractors to bid RCA as an option? Explain answer and why.

  12. Are contractors provided the flexibility to make the decision to utilize RCA when the material meets standard specification requirements, or does the state require additional approvals and testing?

  13. Describe feed system into plant for recycled materials?

  14. Source approval for recycled material and other virgin material?

  15. What type of mixer is used, central mixer, truck mixer or portable mixer?

  16. What types of admixtures are typically used? Any special considerations with the recycled concrete?

  17. Use of other recycled materials such as fly ash, foundry sand, and GGBF slag in this mixture?

  18. Any other types of special considerations at the plant when using a recycled concrete material?

  19. Provide a brief description of various markets for RCA in your service area and recent production, usage and pricing trends.

  20. Provide details of any ongoing, completed or compiled research and demonstration projects regarding RCA.

  21. Describe any instances where the use of RCA was precluded in a project and the circumstances of the situation.

  22. Provide details on any problems that have occurred at your facility or a project site using RCA. Describe any corrective actions, monitoring and follow-up employed to address any problems or concerns.

  23. Detail any ongoing concerns or barriers regarding the use of RCA in the various applications that would benefit from further laboratory work, field testing, or policy clarification.

  24. What barriers have you overcome and how was that achieved?

  25. Are there any construction issues different for RCA and virgin aggregates?

  26. Describe the closure and post-closure monitoring and maintenance requirements applicable to construction activities with RCA.

Estimated Time: 2 hours

 
Updated: 04/07/2011
 

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