Fly ash or natural pozzolans meeting this requirement are considered as effective in controlling alkali silica reactions as the use of the low-alkali control cement used in the evaluation. ASTM C618-12a(Standard Specification for Coal Fly Ash and Raw or Calcined Natural Pozzolan for Use in Concrete)Class N-Raw or calcined natural pozzolans that comply with the applicable requirements for the class as given herein, such as some diatomaceous earths; opaline cherts and shales; tuffs and volcanic ashes or pumicites, calcined or uncalcined; and various materials requiring calcination to induce satisfactory properties, such as some clays and shales.SiO2+Al2O3+Fe2O3 :70% max,SO3: 4% max,Moisture content: 3% max,LOI: 10% max,Fineness: +45 micron sieve:35% max,Bulk Density:2% maxClass F-Fly ash that meets the applicable requirements for this class as given herein. This class of fly ash has pozzolanic properties.SiO2+Al2O3+Fe2O3 :70% max,SO3: 5% max,Moisture content: 3% max,LOI: 6% max,Fineness: +45 micron sieve:35% max,Bulk Density:2% maxClass C-Fly ash that meets the applicable requirements for this class as given herein. This class of fly ash, in addition to having pozzolanic properties, also has some cementitious properties.SiO2+Al2O3+Fe2O3 :50% max,SO3: 5% max,Moisture content: 3% max,LOI: 6% max,Fineness: +45 micron sieve:35% max,Bulk Density:2% max