Benchmarking Accelerated Laboratory Tests for ASR to Field Performance: Consideration of Cement and Alkali Contents and Influence of SCMs

Developing new test methods and benchmarking existing laboratory test methods for assessing alkali-aggregate reactivity and preventive measures remain a major challenge to the concrete and aggregate industry. The recently developed AASHTO R 80-17 practice (previously AASHTO PP 65) and ASTM C1778-16 Guide have significantly improved the way the concrete industry assesses aggregates for potential alkali-silica reactivity and selects appropriate mitigation means to allow the use of potentially alkali-silica reactive aggregates in new concrete construction. These documents were a result of a number of FHWA- and DOT-funded research projects on evaluating the potential for, and the prevention of, alkali-silica reaction together with a consideration of the current approach by the Canadian Standards Association. A unique feature of these projects was the use of long-term outdoor exposure sites to benchmark accelerated laboratory tests to concrete exposed to actual environmental fluctuations. The investigated concrete mixtures primarily followed mixture proportions specified in ASTM C 1293, including cement and alkali contents. This is often regarded as our most reliable test method for assessing aggregate reactivity. As a result, the current guidance documents (AASHTO PP 65 and ASTM C 1778) are based on mixtures that have high cement [708 lb/yd³ (420 kg/m³)] and high alkali (0.95% or 1.25% Na2Oeq) contents. However, there is criticism that they do not properly capture concrete mixtures with lower cement contents [for example, <708 lb/yd³ (<420 kg/m³)] and/or lower alkali loadings. Also, recent results from long-term exposure sites indicate that the amount of supplementary cementitious materials (SCMs) needed to control ASR expansion in the concrete prism test (ASTM C1293) or that required when simply following the AASHTO R 80-17 practice or ASTM C1778 guide may not be adequate to control expansion in outdoor exposure blocks with high contents of high-alkali cements. Testing SCM mixtures in exposure blocks with more moderate (and realistic) alkali levels is needed to ascertain whether this is merely an artifact of the severe alkali loadings used in previous exposure-block studies. The main objectives of this research are (1) to extend the current database from field-exposure blocks produced with cement contents and alkali loadings representative of highway pavements and structures for the purpose of validating and/or calibrating the prescriptive (preventive) measures in AASHTO R 80-17 and ASTM C1778 and (2) to enable better benchmarking of the various “performance tests” or “job-mixture tests” that have been or are being developed currently. To achieve these objectives, concrete blocks will be cast and exposed to real environmental conditions with moderate alkali loadings and lower cement contents to provide the crucial long-term benchmarking for the development of ASR test methods for job mixtures and to validate and/or calibrate the prescriptive measures in AASHTO R 80-17 and ASTM C1778. Various modified accelerated test methods that show promise for assessing aggregate reactivity and potential mitigation options will also be investigated.

Language

  • English

Project

  • Status: Proposed
  • Funding: $650000
  • Contract Numbers:

    Project 10-103

  • Sponsor Organizations:

    American Association of State Highway and Transportation Officials (AASHTO)

    444 North Capitol Street, NW
    Washington, DC  United States  20001

    National Cooperative Highway Research Program

    Transportation Research Board
    500 Fifth Street, NW
    Washington, DC  United States  20001

    Federal Highway Administration

    1200 New Jersey Avenue, SE
    Washington, DC  United States  20590
  • Project Managers:

    Jawed, Inam

  • Start Date: 20180619
  • Expected Completion Date: 0
  • Actual Completion Date: 0

Subject/Index Terms

Filing Info

  • Accession Number: 01672254
  • Record Type: Research project
  • Source Agency: Transportation Research Board
  • Contract Numbers: Project 10-103
  • Files: TRB, RiP
  • Created Date: Jun 18 2018 3:03PM