Specifications include, but are not limited to: Contracts with one or more companies that can provide HIGHWAY ROCK SALT. 2.1. CHEMICAL COMPOSITION: Any one or combination of the 3 following chlorides: (NaCl, CaCl2, and MgCl2 as NaCl based on dry weight and shall conform to a chemical composition of a minimum of 95%. 2.2. UNIT OF MEASUREMENT: TON. The term ton shall mean the “short ton”, an avoirdupois unit equal to 2000 pounds. 2.3. GRADATION: Salt shall conform to the following particle size distribution specifications as determined by laboratory sieves per ASTM D632 (testing method is AASHTO T27 for gradation): • Passing a ½” sieve 100% • Passing a 3/8” sieve 95% - 100% • Passing a No.4 sieve 20% - 90% • Passing a No. 8 sieve 10% - 60% • Passing a No. 30 sieve 0% - 15%