Investigation of hydraulic activity of ground granulated blast furnace slag in concrete

Ground granulated blast furnace slag (GGBFS), a by-product of the steel manufacturing industry, being used as an effective partial cement replacement material, has already been proven to improve several performance characteristics of concrete. The reactivity of GGBFS has been found to depend on the properties of slag, which vary with the source of slag, type of raw material used, method and the rate of cooling. The present work aims at bringing out a novel relationship between the Hydraulic Index (HI) of slag at 7 and 28 days (HI7 and HI28) and the influencing properties of slag, namely, glass content, fineness and chemical composition by employing multiple regression analysis on 37 slag samples from various sources. HI7 and HI28, thus obtained, have been mapped onto a Slag Activity Index (SAI) plot, giving an indication of the ranges of strength of slag.