Reuse of Abandoned Shield Residues Stabilized by a Sustainable Binder: Assessment of Strength, Durability, and Environmental Properties

The resourceful reuse, construction, and environmental and safety hazards of shield residues in underground construction have received a lot of attention. This paper reports the assessment of shield residues generated with the underground space development through stabilization. The variations of strength, durability, and environmental properties of magnesium oxide (MgO)-activated ground granulated blast furnace slag (GGBS)-fiber material stabilized shield residues are tested by unconfined compressive strength test, direct shear test, pH test, and modified dry and soaking cycle test (acidic sulfate ion condition, pH = 5.0). Portland cement (PC)-stabilized shield residues are selected as the control group. The optimal ratio of MgO-activated GGBS-fiber-stabilized material is recommended. The test results show that the basalt fiber with 12 mm length and 0.1% ratio is designed as the optimal value. The MgO-activated GGBS-fiber-stabilized shield residues specimens with the ratio of MgO to GGBS of 1:7 display higher unconfined compressive strength (q(u)) and shear strength (tau). After ten dry-soaking cycles, the q(u), tau, and pH of the MgO-activated GGBS-fiber-stabilized shield residues specimens decreased by 21%, 8%, and 12%, respectively, compared to those corresponding to the standard curing time. In contrast, the q(u), tau, and pH of the control group were reduced by 46%, 39%, and 13%.