Reactivity of Granulated Blast Furnace Slag

The Algerian iron and steel complex of El Hadjar, near the city of Annaba, produces a granulated blast furnace slag (GBFS) mainly used by the local cement factories as an addition to clinker of up to 30 % as maximum content, for manufacturing a compound CEM II type cement (Algerian Standard).

With the aim, on the one hand, of limiting the use of high clinker content in Algerian cement plants and replacing it with other constituents such as granulated blast furnace slag and, on the other hand, to use this slag as an addition to local concrete, we have attempted to characterize it according to its degree of reactivity.

The use of chemical activity indexes and caustic soda tests lead to disappointing results that are contradicted by the results obtained on mortar within the scope of the standard determination of a hydraulic efficient index. The results obtained indicated that the classification of El Hadjer slag strongly depends on its degree of fineness; it also has weak short-term activity, denoting a slower kinetics of reaction compared to classical slag. These results permit us to recommend a minimal Blaine of 3500 cm2/g for this slag.

A more intensive use of this slag in cement and concrete is undoubtedly possible, but this must be demonstrated by conducting tests on mortar and validating by a study on concrete.