Improving Guidance of AASHTO R 80/ASTM C 1778 for Alkali-Silica Reactivity (ASR) Potential and Mitigation

The realistic assessment of alkali-silica reactivity (ASR) and identification of preventive measures remain major challenges to the concrete and aggregate industry. The recently developed AASHTO R 80 Practice (previously AASHTO PP 65) and the American Society for Testing and Materials ASTM C 1778 Guide have significantly improved the way the concrete industry assesses aggregates for potential ASR and selects appropriate mitigation means to allow the use of potentially reactive aggregates in new concrete construction. These publications were a result of a number of FHWA- and state departments of transportation (DOTs)-sponsored studies on evaluating the potential for, and the prevention of, ASR as well as a consideration of the current approach by the Canadian Standards Association. The above-mentioned studies used long-term outdoor exposure sites to benchmark accelerated laboratory tests to concrete exposed to actual environmental fluctuations. These studies investigated concrete mixtures primarily that followed mixture proportions specified in ASTM C 1293, including cement and alkali contents, which is often regarded as the most reliable test method for assessing aggregate reactivity. As a result, the current guidance documents (AASHTO R 80 and ASTM C 1778) are based on mixtures that have high cement [708 lbs./yd³ (420 kg/m³)] and alkali (0.95% or 1.25% Na₂Oeq) contents. However, the issue has been raised that they do not properly capture concrete mixtures with lower cement contents [for example, <708 lbs./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 C 1293) or that required according to the AASHTO R 80 Practice or ASTM C 1778 Guide may not be adequate to control expansion in outdoor exposure blocks with high contents of high-alkali cements. Furthermore, testing SCM mixtures in exposure blocks with more moderate (and realistic) alkali levels is needed to ascertain whether or not this is merely an artifact of the severe alkali loadings used in previous exposure-block studies. The objectives of this research are to improve guidance in AASHTO R 80 and ASTM C 1778 through: (1) Constructing and evaluating field exposure blocks with varying concrete materials placed in diverse environmental conditions to supplement the existing information. (2) Enabling better benchmarking of current performance and job-mixture tests that have been or are being developed currently.

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: 20190318
  • 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