FLY ASH AS POZZOLANA & AS ADMIXTURE

There is sufficient evidence to indicate that fly ash with loss on ignition value up to 12% may be used for part replacement of cement (up to 30 % of cement).
Fly ash shall be supplied in the following grades.
Grade I: For incorporation in cement mortar and concrete and in lime pozzolana mixture, and for manufacture of Portland pozzolana cement.
Grade II: For incorporation in cement mortar and concrete and in lime pozzolana mixture.
Fly ash may be extracted from flue gases of ground or pulverized coal or lignite fired boilers by any suitable process, such as by cyclone separation or electrostatic precipitation; bottom ash from the boilers shall not be added to the fly ash.
  CHEMICAL REQUIREMENTS {as per IS: 3812}
(i) Silicon dioxide (SiO2) plus aluminum oxide (Al203) plus iron oxide (Fe203), percent by mass, Minimum = 70.0
(ii) Silicon dioxide (SiO2), percent by mass, Minimum = 35.0
(iii) Magnesium oxide (MgO), % by mass, Max = 5.0
(iv) Total sulphur as sulphur trioxide (SO3), Max. percent by mass = 2.75
(v) Available alkalis as sodium oxide (Na20), percent by mass, Max. = 1.5
(vi) Loss on ignition, percent by mass Max. = 12.0
  PHYSICAL REQUIREMENTS {as per IS: 3812}
(i) Fineness: Specific surface in m2/kg by Blaine's permeability method. 
Min. = 320 for Grade I & 250 for Grade II.
(ii) Lime reactivity: Average compressive strength in N/mm2,
Min. = 4.0 for Grade I & 3.0 for Grade II.
(iii) Compressive strength at 28 days in N/mm2 Min. = Not less than 80 percent of the of the corresponding plain cement mortar cubes.
(iv) Drying shrinkage, percent, Max. = 0.15 for Grade I & 0.10 for Grade II.
(v) Soundness by autoclave test expansion of specimens, percent, 
Max. = 0.80 % for both Grades.