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Rationale

A sulfate test method does not exist for coarse-grained material. ASTM C1580 Standard Test Methods for Water-Soluble Sulfate in Soil, ASTM D8459 Standard Test Methods for Detecting Water Soluble Sulfates in Construction Soils, and AASHTO T290 Determining Water-Soluble Sulfate Ion Content in Soil, are not applicable for coarse-grained material as it requires the material to be crushed to pass a 600 µm sieve (C1580) or screened over the No. 10 (2-mm) sieve (T290) to remove larger particles. It is not appropriate to crush the coarse-grained material so that it passes the designated sieve, as doing so alters the sulfate and would 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, WK93649, addresses chloride ion content in granular materials.