Magnesia reactivity on activating efficacy for ground granulated blastfurnace slag for soft clay stabilisation

• Reactive MgO-activated GGBS is used for soft clay stabilisation.
• MgO reactivity affects GGBS activation.
• High MgO reactivity has high GGBS activating efficacy.
• Excessive MgO with high reactivity has negative effect on strength.

Three types of magnesia (MgO) with varying reactivity were used to activate ground granulated blastfurnace slag (GGBS) for soft clay stabilisation; the effect of MgO reactivity on the stabilisation efficacy was investigated. A range of tests were employed to study the mechanical and microstructural properties of the stabilised clays, including unconfined compressive strength, X-ray diffraction, scanning electron microscopy and mercury intrusion porosimetry. The results indicated that MgO with high reactivity had high activating efficacy for GGBS, and accelerated the strength development rate of stabilised clay; however, excessive MgO with high reactivity also had negative effect on its strength performance. Hence, low content of MgO with high reactivity is suggested for soft clay stabilisation application.