Magnesium sulfate attack on clays stabilised by carbide slag- and magnesia-ground granulated blast furnace slag

Carbide slag (CS)- and reactive magnesia (MgO)-activated ground granulated blast furnace slag (GGBS) were used to stabilise soft clay subjected to accelerated magnesium sulfate (MgSO4) attack. The results indicated that the CS-GGBS-stabilised clay had a higher resistance to magnesium sulfate attack than magnesia-GGBS-stabilised clay; this was contrary to findings from a previous study subjected to sodium sulfate attack. The formation of gypsum and the decomposition of calcium silicate hydrate (CSH) occurred in both stabilised clays after the magnesium sulfate attack, which is primarily responsible for the deterioration. Since the magnesia-GGBS-stabilised clay had a lower pH buffering capacity and calcium/silicon ratio of CSH than CS-GGBS-stabilised clay, it was more susceptible to magnesium sulfate attack.