Sulfate soil stabilisation with binary blends of lime– silica fume and lime– ground granulated blast furnace slag

The use of silica fume and ground granulated blast-furnace slag (GGBS) as a precursor to lime has been proven to be an effective sulfate soil stabilisation technique. However, which precursor is superior, in terms of both strength and swelling, is still questionable. Accordingly, the binary blends of lime–silica fume and lime–GGBS were separately added to pure kaolin soil and sulfate-dosed kaolin soil at a fixed combination dosage of 3L7S and 3L7GGBS. Then, a multi-scale investigation including unconfined compression strength (UCS), linear expansion, derivative thermogravimetric (DTG), x-ray diffraction and scanning electronic microscopy (SEM), was performed to assess their performance. The engineering tests indicated that the binary blends of lime–silica fume and lime–GGBS are effective in the stabilisation of non-sulfate and sulfate-dosed soil, with the former being superior in terms of the expansion and the latter being superior in terms of UCS. This disparity in performance is partly attributed to the higher calcium oxide content of 3L7GGBS which induces a relatively higher amount of ettringite, and partly due to the higher pozzolanic activity of silica fume which accelerates the consumption of lime and restricts the formation of ettringite on the expense of fabric modification.