Characterization of Coarse Backfill Materials for Prevention of Corrosion of MSE Metallic Wall Reinforcement

The service life of mechanically stabilized earth (MSE) walls depends on the rate of corrosion of the metallic reinforcements used in their construction. Assessment of corrosion potential requires the accurate evaluation of pH, resistivity, and ionic (e.g., sulfate and chloride) concentrations of aqueous solutions in contact with the surrounding aggregate. There is a tendency to utilize larger-size aggregates that contain only a small amount of fine material (passing No. 40 sieve) in the backfill. Evaluation of the electromechanical parameters of coarse aggregates is challenging because traditional methods utilize only fine-grained material. The effectiveness of traditional soil characterization techniques for use with coarse aggregates was evaluated by performing leaching experiments with coarse limestone and dolomite aggregates from six materials in Texas. Chemical differences were isolated from size-related kinetic leaching effects by comparing results from the same-sized material collected in the field versus material derived from the crushing of larger (>= 3/8 in.) aggregates in the laboratory. Testing demonstrated that fines collected from the field were enriched in chemicals that when exposed to water decreased pH and resistivity and increased chloride or sulfate concentrations relative to the bulk rock. This phenomenon can bias traditional soil testing results and therefore the assessment of corrosion potential. In this report a more representative geochemical testing protocol is recommended. The rate of corrosion was primarily controlled by the chloride content developed from the geochemistry of the backfill and the rate was predicted from the measured conductivity, as well as a two-step corrosion model was determined for the MSE.

Language

  • English

Media Info

  • Media Type: Digital/other
  • Pagination: 131p

Subject/Index Terms

Filing Info

  • Accession Number: 01481258
  • Record Type: Publication
  • Report/Paper Numbers: FHWA/TX-11/0-6359-1
  • Files: TRIS, ATRI, USDOT, STATEDOT
  • Created Date: May 10 2013 9:51AM