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Effect of Low and Moderate Recycled Concrete Aggregate Replacement Levels on Concrete Properties

Status: Complete
Contract #: 1036599

Project overview

Recycled concrete aggregate (RCA) has been extensively researched as a way to improve the sustainability of concrete, eliminate construction waste, and address looming shortages of virgin coarse aggregates. However, the goal of most research is to investigate high replacement levels and maximize the amount of RCA in the concrete. In reality, many agencies do not have access to enough RCA to use high replacement levels because RCA is in high demand for other applications, such as granular bases. Additionally, many agencies are reluctant to explore high replacement levels because of known concerns with the use of high replacement levels of RCA.

The goal of this research is to investigate the effect low and moderate replacement levels of coarse RCA for virgin coarse aggregate in concrete for paving applications. Low and moderate replacement levels are most likely to be implemented because they do not require as much RCA and they may be perceived to have less risk to owners. Therefore it is important to understand how these replacement levels will affect the mechanical and non-mechanical properties of the concrete. This research will investigate the effect of up to three different RCA coarse aggregate types at various low and moderate replacement levels (10-50%). Tests conducted will measure properties that are often used in performance specifications, as given in AASHTO PP 84-19.


Task 1: Initial memorandum on expected research benefits and potential implementation steps

During the proposal phase and the development of the work plan, key benefits were selected to clearly define the benefits the state will receive from the results and conclusions of this research. This task will provide an initial assessment of research benefits, a proposed methodology, and potential implementation steps.

  • Scheduled Date to Submit Draft Deliverable: 9/1/2020
  • Deliverable: A memorandum (PDF) providing initial estimates of expected research benefits, documentation of the methodology, and potential implementation steps.

Task 2: Literature Review

Conduct a complete review of the literature to better understand the state of the art related to using recycled aggregates and identify gaps in research associated with testing RCA at lower replacement levels and the effects of RCA on properties commonly used in performance specifications and/or pavement design.

Task 3: Materials acquisition and mix design development

Acquire materials required for the project (recycled aggregate, control aggregate, cement, admixtures, etc.) Based on information from the literature review in Task 2, develop mix designs that can be used for testing. This will require the following testing to characterize the aggregates: Gradation (ASTM C136), Specific gravity and absorption (ASTM C127), and Moisture content (ASTM D2216).

Task 4: Concrete mixing and testing

Using the finalized mix designs developed in Task 3, cast test specimens and conduct testing.

Fresh tests:
  • Air content
  • SAM number
  • Box test
Hardened tests:
  • Compressive strength gain
  • Flexural strength gain
  • Elastic modulus and Poisson’s ratio
  • Coefficient of thermal expansion
  • Surface resistivity
  • Shrinkage
  • Freeze-thaw durability
  • Digital image correlation


Task 5: Data Analysis

Compare test results for all mixes to determine the effects of using different RCA replacement levels. A statistical analysis will be conducted to determine the significance of the results.

Task 6: Final Memorandum on Research Benefits and Implementation Steps

Draft memo outlining conclusions of the research, their benefits, and the steps required for implementation

Task 7: Draft Final Report

Draft final report describing testing methods and results.

  • Scheduled Date to Submit Draft Final Report for TAP review: 12/1/2022
  • Deliverables: Draft final report

Task 8: Editorial Review and Publication of Final Report

Editorial Review and Publication of Final Report

Project team

Email the Project Team
Principal Investigator(s): Rita Lederle, Ph.D., P.E., Assistant Professor, University of St. Thomas – Civil Engineering, rita.lederle@stthomas.edu
Technical Liaison: Bernard Izevbekhai, MnDOT, bernard.izevbekhai@state.mn.us
Project Technical Advisory Panel (TAP):

  • John Cunningham, ARM of MN
  • Dulce Rufino Feldmann, Caltrans
  • Dan Gancarz, Illinois Tollway
  • Bernard Izevbekhai, MnDOT (TL)
  • Maria Masten, MnDOT
  • Brett Trautman, MoDOT

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