Use of recycled concrete aggregate in new concrete mixes

Concrete production continuously consumes natural virgin aggregate (NVA), which has gradually exhausted this natural resource especially near larger cities in the US. There are growing needs for replacing NVA with more sustainable materials. Recycled concrete aggregate (RCA) deserves serious considerations because it offers dual benefits of saving landfill space as well as creating a cheaper and more sustainable alternative. Although the use of RCA in non-structural applications such as fill, pavement base, foundation, and sidewalk has gained wide acceptance, its use in structural concrete such as pavement slabs has been exceptionally limited mostly due to concerns over RCA quality and wide variations in its sources. These major concerns are further aggravated by the lack of knowledge on its long-term performance as well as the absence of standards and specifications for its use. The uncertainty over RCA usage make it possible for material engineers to overlook the opportunities of using RCA in new concrete mixes. Currently, only two national standards, ASTM C331 and AASHTO MP162, specify the use of RCA, however, the information is inexplicit or the limit is too stringent. For examples, ASTM C33 permits the use of RCA as aggregate in concrete, but there is no information on how to classify RCA. Even in AASHTO MP16, which possibly represents the most detailed guidelines addressing the use of RCA in concrete today, the requirements for RCA are simply the same as those for NVA. Clearly, these requirements are too high and unnecessary for pavement applications because typical paving concrete (e.g., TDOT class CP) only requires a 28-day compressive strength of 3000 psi. On the other hand, the use of this standard would restrict the wider application of RCA in transportation structures. As a result, research is essential to investigate how different qualities of RCA affect the performance of new concrete mixes with the goal of developing performance-based specifications for the best use of RCA in the transportation system. Tennessee Department of Transportation (TDOT) always advocates sustainable and cost-effective construction practices. The motivation for promoting RCA in TDOT new concrete mixes is the same: negative impact of quarrying operations on Tennessee environment, increased cost for long hauling distances, limited space for landfill in Tennessee, conservation of natural resources, and reduced carbon footprint. Realizing so many benefits, Tennessee transportation communities are increasingly embracing the sustainable RCA usage. Similarly, very limited information is available in Tennessee regarding RCA qualification and classification as well as its applications. It is the intention of this project to develop methods and criteria for adequately qualifying RCA from different sources throughout Tennessee and to explore the suitability of various RCAs for TDOT new concrete mixes.

    Language

    • English

    Project

    • Status: Active
    • Funding: $219,281.00
    • Contract Numbers:

      RES2020-06

      40100-07219

    • Sponsor Organizations:

      Tennessee Department of Transportation

      James K. Polk Building
      Fifth and Deaderick Street
      Nashville, TN  United States  37243-0349
    • Managing Organizations:

      Tennessee Department of Transportation

      James K. Polk Building
      Fifth and Deaderick Street
      Nashville, TN  United States  37243-0349
    • Project Managers:

      Porter, Jeffry

    • Performing Organizations:

      Middle Tennessee State University, Murfreesboro

      1301 East Main Street
      Murfreesboro, TN  United States  37132-0001
    • Principal Investigators:

      Yang, Zhifu

      Brown, Heather

    • Start Date: 20190701
    • Expected Completion Date: 20201130
    • Actual Completion Date: 0
    • USDOT Program: Transportation, Planning, Research, and Development

    Subject/Index Terms

    Filing Info

    • Accession Number: 01744169
    • Record Type: Research project
    • Source Agency: Tennessee Department of Transportation
    • Contract Numbers: RES2020-06, 40100-07219
    • Files: RiP, STATEDOT
    • Created Date: Jun 26 2020 9:24AM