One-part and two-part alkali-activation of iron mining tailings for sustainable 3D concrete printing mixes

3D Concrete printing (3DCP) is a key technology for the future of civil engineering. Its main advantages are the reduction of labor costs and ac-celerated construction process. However, the mixes still need improvements concerning sustainability. Sustainable and affordable mixes for 3DCP may be based on mining residues, either fine overburden materials (OM) as binders or fine quartz tailings as aggregates. The OM can be alkali-activated by the one-part (“just add water”) or two-part alkaline activation methods. The first con-sists of using a solid activator mixed with the powdered binder; water and ag-gregates are then added, just like Portland cement mortar and concrete produc-tion. The two-part method contains the alkaline activator in a separate aqueous solution that is mixed to the binder and aggregates to produce the alkali-activated material (AAM). The one-part method is simple and safer, but some-times leads to inhomogeneous mixes as the dispersion of powdered activator is difficult. This paper presents preliminary results of OM as main binder for AAM. A fine quartz tailing is used as single fine aggregate. The mixes were prepared to be potentially used as mortars for 3DCP. Therefore, they were compared with a commercial PC-based 3DCP mortar. The properties assessed were consistency, extrudability and compressive strength development. SEM was used to show the differences in the microstructure of one-part and two-part OM-based AAM, compared with the commercial mortar. The results show promising low-carbon mixes to be employed for 3DCP.