ABSTRACT It is a very well known fact that the use of fly ash in masonry and concrete make the structures durable. Properties of Fly Ash depend upon coal source. For acceptability of fly ash in cement, mortar and concrete various specifications and standards are available. The Indian standard IS 3812: 2003(Part I and Part II) expects some physical and chemical properties similar to world standards, while differs in some, like lime reactivity test. As a part of research activity the authors have collected 23 different fly ash samples from various hoppers of three power stations near Nagpur. The samples were tested as per most of the provisions of IS 3812 and tests specified in IS 1727. Test results are compared with major world standards and specifications. Gain of strength is the most important character of fly ash, especially from the usage in cement and concrete. The paper discusses comparison of various standard specifications and interpretation of pozzolanic reactivity.