Condition Evaluation of In-Service Chemically Stabilized Subgrades in a High Sulfate Environment

This project included measurements of strength properties, soil properties, and chemical content of natural and chemically stabilized subgrade soil from five projects across Ohio, three from sites that have historically had high sulfate content, and two that have not. The objective was to compare the properties of the soils from the sites and determine if there were crystals of ettringite or thaumasite in the soil, which would indicate potential for heaving. Site testing included portable seismic properties analyzer (PSPA), falling weight deflectometer (FWD), lightweight deflectometer (LWD), dynamic cone penetrometer (DCP), standard penetration testing (SPT), an informal distress survey, and collection of soil specimens for laboratory analysis, which included standard soils tests (Grain size, Atterberg limits, organic content, moisture content, pH, and sulfate content as determined in Ohio Supplement 1122), and chemistry analysis comprising neutralization potential, and X-ray diffraction. In the control sections, measured sulfate levels were low in the natural subgrade and higher in the stabilized subgrade but still below the criterion of concern at 3000 ppm. In the high sulfate sections, natural subgrade had still higher sulfate content, but still usually below 3000 ppm, while the stabilized subgrade generally had content above 3000 ppm, but no more than 6500 ppm to 9500 ppm depending on the site. However, the X-ray diffraction found no measurable quantity of ettringite or thaumasite crystals, indicating that conditions for formation were not met at any of the sites. The pH of stabilized soil at all locations was just above 10, which was one condition that was met. None of the pavements showed any signs of damage due to sulfate heaving. The continued practice of global stabilization of subgrade soil is recommended. The undercut section on LAK-2 showed less variability than the other section, and this approach may be considered where cost effective.


  • English

Media Info

  • Media Type: Digital/other
  • Edition: Final Report
  • Features: Appendices; Figures; Maps; Photos; References; Tables;
  • Pagination: 216p

Subject/Index Terms

Filing Info

  • Accession Number: 01685236
  • Record Type: Publication
  • Report/Paper Numbers: FHWA/OH-2017/41
  • Contract Numbers: State Job No. 135443
  • Created Date: Nov 12 2018 5:15PM