Study on the Performance of 3D-Printed Alkali-Activated GGBS and FA Mortar with Steel Slag Sand as Aggregate

Abstract In response to the high environmental load and dependence on natural aggregates in traditional 3D-printed cement-based mortars, this study develops an alkali-activated 3D-printing mortar using industrial solid wastes such as ground granulated blast-furnace slag (GGBS), fly ash (FA), and steel slag sand as raw materials, aiming to promote the sustainable utilization of green building materials. The study systematically tests the working performance (flowability, shape retention, extrudability, buildability), mechanical properties (cube compressive strength and anisotropy), and combines X-ray diffraction and scanning electron microscopy analyses to reveal the hydration products and microstructural characteristics. The results indicate that the FA content and activator modulus significantly affect the mortar flowability, with the best shape retention and buildability at a flowability range of 170–220 mm. The cube compressive strength of the steel slag sand mortar increases with the GGBS content, reaching a maximum strength of 67.94 MPa at 28 days. Microstructural analysis shows the formation of C─(A)─S─H gel and the reinforcing effect at the interface of steel slag sand. This study provides a theoretical basis for applying 3D-printing materials entirely composed of industrial solid wastes in engineering, thereby advancing the synergistic combination of green building materials and sustainable construction practices.