ASTM International

Standard Test Methods for Water-Soluble Chlorides Present as Admixtures in Graded Aggregate Road Mixes
 N D1411

Annotation

These test methods are applicable to the determination of water-soluble calcium, magnesium, and sodium chlorides used as admixtures in the preparation of graded aggregate road materials.

Method A, Total Chlorides—Add an excess of a standard silver nitrate solution to the filtered sample; back titrate the excess silver with a standard ammonium thiocyanate solution to a red-orange endpoint using Volhard indicator.

Method B, Calcium Chloride—Calcium in an alkaline solution is titrated with standard EDTA solution using calcein modified as an indicator. The color change is from green to blue.

Method C, Magnesium Chloride—Calcium and magnesium, in a solution buffered to a pH of 10, are titrated with standard EDTA solution using eriochrome black T as an indicator. The color change is from red to blue. Magnesium chloride is calculated by subtracting the EDTAcalcium equivalent volume determined in the analysis for calcium chloride from the total EDTA volume used, to obtain the magnesium EDTA equivalent by difference.

Method D, Alkali Chloride—Alkali chlorides are calculated from the difference of the total chloride and calcium and magnesium determinations.

NOTE 1—These test methods assume that the aggregate did not contain significant amounts of the water-soluble chlorides in question before the admixture was added. If significant amounts of these chlorides are known or suspected to be present, the aggregate shall be tested for these constituents according to these test methods and the proper corrections made.

All observed and calculated values shall conform to the guidelines for significant digits and rounding established in Practice D 6026.