This Indian Standard was adopted by the Bureau of Indian Standards, after the draft finalized by the Cement and Concrete Sectional Committee had been approved by the Civil Engineering Division Council. The Indian Standard, IS12089 : 1987 ‘Specification for granulated slag for the manufacture of Portland slag cement’ covers requirements for granulated slag. However, a need to have a separate standard on ground slag suitable for use in Portland cement by blending process, and for making concrete by direct addition was felt. This new Indian standard on ground granulated blast furnace slag (GGBS) has, therefore, been formulated to fulfill this need. The composition of the Committee responsible for the formulation of this standard is given in Annex D. For the purpose of deciding whether a particular requirement of this standard is complied with, the final value, observed or calculated, expressing the result of a test or analysis, shall be rounded off in accordance with IS 2 : 1960 ‘Rules for rounding off numerical values (revised)’. The number of significant places retained in the rounded off value should be the same as that of the specified value in this standard.