National Academies Press: OpenBook
« Previous: Summary
Page 4
Suggested Citation:"Chapter 1 - Introduction." National Academies of Sciences, Engineering, and Medicine. 2005. Guidelines for Early-Opening-to-Traffic Portland Cement Concrete for Pavement Rehabilitation. Washington, DC: The National Academies Press. doi: 10.17226/13543.
×
Page 4

Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

4CHAPTER 1 INTRODUCTION With increasing traffic in urban areas, motorists are becom- ing less tolerant of delays during pavement rehabilitation. To minimize delays, state highway agencies (SHAs) use early- opening-to-traffic (EOT) rehabilitation strategies that mini- mize the time of lane closure. Generally, portland cement concrete (PCC) used in these applications is expected to gain sufficient strength to carry traffic within 6 to 24 hours after placement. Rigorous requirements for strength development have usually been stipulated for EOT concrete applications, often with limited consideration given to materials and con- struction aspects that influence long-term durability. Much of the research conducted on EOT concrete investigated the mechanical properties of the mixtures, but not the durability aspect. Information on the durability of the concrete used in these applications is needed to assess the long-term perfor- mance of the rehabilitated pavement. The unique properties of EOT concrete make it more susceptible to durability-related distress than conventional concrete. For example, the use of high cement contents and multiple admixtures can lead to increased shrinkage, altered microstructure, and unexpected interactions. Further, the abil- ity of standard testing to detect durability problems is limited, and thus deficiencies may go undetected through the mixture design and construction process. Research to address these needs was conducted under NCHRP Project 18-04B, “Durability of ‘Early-Opening-to- Traffic’ Portland Cement Concrete for Pavement Rehabilita- tion.” The research focused on concrete mixtures suited for opening to traffic within (a) 6 to 8 hours and (b) 20 to 24 hours after placement and was limited to full-depth rehabili- tation, such as a full-depth repair and slab replacement. In this project, both field- and laboratory-prepared EOT con- crete mixtures were evaluated. Core specimens from eight mixtures from four states were obtained, and 28 different EOT concrete mixtures were prepared in the laboratory. These mixtures were tested and the results analyzed to assess the properties of the fresh and hardened concrete. The work per- formed under this study provided the basis for the guidelines presented herein. The agency report is available on the web as NCHRP Web-Only Document 76 at www.trb.org/news/ blurb_detail.asp?id=5203. These guidelines include a summary of state-of-the-practice construction techniques and specifications used by state DOTs for EOT concrete materials. Performance considera- tions related specifically to EOT concrete materials—including strength, shrinkage, durability, microstructure, and absorption/ permeability—are discussed. Materials and mixture design considerations are then reviewed along with various test methods used to assess the fresh concrete properties, mea- sures of compressive strength and/or flexural strength, volume change, durability in freeze-thaw environments, absorption/ permeability, and microstructural characterization techniques. A recommended program for material testing during mix- ture design and in the course of related investigations and research is also described. The guidelines are expected to assist engineers in selecting appropriate materials, mixtures, and construction techniques for use in EOT concrete repairs. The next two chapters summarize the state of the practice with regards to EOT concrete materials, placement, and per- formance considerations. Recommendations for selecting materials and testing EOT concrete mixtures are presented in Chapters 4 and 5.

Next: Chapter 2 - State of the Practice for EOT Concrete Repairs »
Guidelines for Early-Opening-to-Traffic Portland Cement Concrete for Pavement Rehabilitation Get This Book
×
MyNAP members save 10% online.
Login or Register to save!
Download Free PDF

TRB’s National Cooperative Highway Research Program (NCHRP) Report 540: Guidelines for Early-Opening-to-Traffic Portland Cement Concrete for Pavement Rehabilitation examines the proportioning, testing, construction, and other aspects of early-opening-to-traffic (EOT) concrete.

  1. ×

    Welcome to OpenBook!

    You're looking at OpenBook, NAP.edu's online reading room since 1999. Based on feedback from you, our users, we've made some improvements that make it easier than ever to read thousands of publications on our website.

    Do you want to take a quick tour of the OpenBook's features?

    No Thanks Take a Tour »
  2. ×

    Show this book's table of contents, where you can jump to any chapter by name.

    « Back Next »
  3. ×

    ...or use these buttons to go back to the previous chapter or skip to the next one.

    « Back Next »
  4. ×

    Jump up to the previous page or down to the next one. Also, you can type in a page number and press Enter to go directly to that page in the book.

    « Back Next »
  5. ×

    To search the entire text of this book, type in your search term here and press Enter.

    « Back Next »
  6. ×

    Share a link to this book page on your preferred social network or via email.

    « Back Next »
  7. ×

    View our suggested citation for this chapter.

    « Back Next »
  8. ×

    Ready to take your reading offline? Click here to buy this book in print or download it as a free PDF, if available.

    « Back Next »
Stay Connected!