Suppressing Ettringite-Induced Swelling of Gypseous Soil by Using Magnesia-Activated Ground Granulated Blast-Furnace Slag

Ettringite usually is formed in lime- and cement-stabilized gypseous soils, resulting in significant swelling upon wetting and thereby causing damage to pavements and foundation systems. To reduce the ettringite formation and the associated swelling, magnesia (MgO)-activated ground granulated blast-furnace slag (GGBS) was investigated for stabilizing gypseous soil. Experimental tests, including swelling, unconfined compression strength, X-ray diffraction (XRD), and scanning electron microscopy (SEM) studies, were conducted to examine properties of MgO-GGBS-treated gypseous soil. Test results illustrated that the swelling of MgO-GGBS-stabilized soils (0.4%–2%) was much lower than that of cement-stabilized soil (6.1%), whereas the strength of MgO-GGBS-stabilized soils after soaking (1.2–2.8 MPa) was significantly higher than that of cement-stabilized soil (0.3 MPa). XRD and SEM results showed that no ettringite was formed in MgO-GGBS-stabilized soils, which primarily was responsible for the lesser swelling and higher strength compared with that of the cement-stabilized soil after soaking. Overall, test results indicated the potential of MgO-GGBS for effective stabilization of gypseous soils.