Development of sustainable foamed alkali-activated materials for modular construction

The production of non-structural parts for modular construction demands a material which combines low density and suitable mechanical strength-foam products are a feasible option. Alkali-activated materials (AAM) have been highly studied in the past decades as potential sustainable binders. Steel slag (SS) has little commercial application and could be applied as possible sustainable binder alternative to ground granulated blast furnace slag (GGBFS) in AAM. This paper studied GGBFS/SS-based foamed AAM (FAAM) applying a mechanical foaming method and analyzed the effect of different quantities of the surfactant (0, 0.25, 0.5, 0.75, 1 and 2%) in the density, compressive strength, porosity and in the porous microstructure. The results have shown that the replacement of 35% GGBFS with SS reduced the compressive strength in 38.1% at 28 days, due to the lower reactivity of SS compared to GGBFS. When the surfactant is added at 2%, the statistical analysis confirmed that the use of SS does not affect porosity. The density reduced equally for GGBFS and GGBFS/SS FAAM (from 1.80 to 1.44 g/cm(3) and from 1.82 to 1.42 g/cm(3), respectively). The reduction in compressive strength of the different matrices is, however, significantly different: from 46.89 to 22.55 MPa for GGBFS FAAM and from 29.02 to 13.78 MPa for GGBFS/SS FAAM at 28 days. Nevertheless, SS may be potential sustainable candidate as partial replacement to GGBFS in the development of sustainable FAAM, as the lowest strength of GGBFS/SS (13.78 MPa) is still acceptable when higher surfactant content is employed (2%).