Using Slag for Unfired-Clay Masonry-Bricks

This paper reports on an investigation on the use of ground granulated blast-furnace slag (GGBS) in the development of a sustainable unfired clay binder material for stabilised masonry-brick. The compressive strength of the stabilised masonry-brick, using a semi-processed industrial kaolinite clay soil and a 'real' clay soil (Lower Oxford Clay) commonly used in masonry clay brick manufacture were examined. In practice between 1 and 3 wt.% lime is needed for modifying the soil properties and between 2 and 8 wt.% lime for stabilisation. Due to the high strength requirement in the building industry in comparison with stabilised highway pavement layers for example, a high maximum stabiliser dosage of 20% was used. However, only a small proportion of this high stabiliser content (20%) was lime or Portland cement. Cylindrical specimens were made at moisture contents of 25, 30, 35 and 40%, and cured for 28 days, before testing for unconfined compressive strength. Preliminary results show that the strength values for the stabilised clay systems investigated were within the strength range of 65 to 2077 kN/m2 at 28 days, with the lime-Portland cement blends tending to achieve lower strength values relative to the lime-slag blends. The results suggest that there is potential for the use of GGBS in unblended binders for the development of unfired clay masonry bricks.