New Test Method for Determining the Water-Soluble Chloride Ion Content in Granular Material used for Embankments, Subgrades, and Retaining Wall Backfill
1. Scope
This test method is for the determination of the water-soluble chloride ion content of as-received granular material that will be used in the field for embankment, subgrade, and retaining wall backfill applications. The method involves measuring chloride ion concentration using a chloride-selective electrode. The principal use of the test method is to supplement soil resistivity measurements to identify conditions under which the corrosion of metal embedded in granular material, or in contact with it, may be sharply accentuated.
NOTE—This test method is partially based on the research conducted by the National Cooperative Highway Research Program (NCHRP) Project 21-11 and the Mineta Transportation Institute (MTI) Project 2225.
Keywords
aggregate; coarse; coarse grained; coarse-grained material; granular; material; chloride
Rationale
A chloride test method does not exist for coarse-grained material. ASTM D512 Standard Test Methods for Chloride Ion in Water and AASHTO T291 Determining Water-Soluble Chloride Ion Content in Soil are not applicable for coarse-grained material, as it requires the material to be crushed to pass a No. 10 (2-mm) sieve (T291) to remove larger particles. It is not appropriate to crush the coarse-grained material so that it passes the designated sieve, as doing so would alter the chloride content and misrepresent the material being used in the field. This document includes modifications offered by Tex-620-M in NCHRP 21-11, Determining pH, Chloride, and Sulfate Contents in Soils. It follows changes approved in D8262, Determining the pH of Granular Materials, and the proposed work order WK71902, Measuring Electrical Resistivity of Granular Material, concerning sampling procedures: a similar work order, WK93648, addresses sulfate ion content in granular materials.
The title and scope are in draft form and are under development within this ASTM Committee.
Work Item Status
Date Initiated: 01-28-2025
Technical Contact: Fariborz Tehrani
Item: 002
Ballot: D18.06 (25-01)
Status: Will Reballot Item