Coarse blast furnace slag as a cementitious material, comparative study as a partial replacement of Portland cement and as an alkali activated cement

The cementitious performance of a coarse granulated blast furnace slag, 2900 cm(2)/g, was investigated in concretes of 230. 280 and 330 kg binder/m(3). First, the slag partially replaced 30%, 50% and 70% of Portland cement, the strength reduced as the amount Of slag increased; however, for high binder contents, similar strengths were attained for lower Portland cement contents. Second, the slag was alkali activated with sodium silicate (moduli 1.7 and 2) at 4%, 6% and 8% %Na2O, the strength increased with the amount of slag in the concrete and developed faster as %Na2O increased. The microstructures of both type of concretes were dense: however, the strengths of activated slag were superior at similar binder loads, indicating that the hydration products of activated slag are of higher intrinsic strength. (C) 2009 Elsevier Ltd. All rights reserved.