CO2-Absorbing 3D Printable Mixtures for Magnesium-Slag Valorization (2024-06)¶

This study proposes carbonatable 3D printing magnesium slag mixtures to reduce preparation cost and CO2 emission compared to conventional 3D printing concrete. Results show magnesium slag slurries with plastic viscosity of 2.05–2.81 Pa·s and yield stress of 297.4–401.75 Pa exhibit suitable extrudability and buildability. Among printable mixtures containing various rheology modifying agents, the printed samples with welan gum (WG) exhibit optimal carbonation reactivity. This is attributed to the three-dimensional threaded network formed by dissolved WG molecules providing channels for calcium ion dissolution, which maintains a sustained carbonation reaction. After 12 h carbonation, the formation of calcite product bonds particles together and fills pores, creating a dense matrix that improves the compressive strength and interlayer bond strength of the MS-WG printed samples to 78.29 MPa and 3.99 MPa, respectively. The foil-like structure of dissolved hydroxypropyl methylcellulose (HPMC) molecules appears to coat magnesium slag particle, restricting calcium ion dissolution and impeding the carbonation reaction. The limited formation of calcite products also contributes to inferior mechanical properties in MS-HPMC printed samples. Additionally, HPMC introduction creates bubble defects within the printed samples, further compromising the mechanical properties of the MS-HPMC printed sample.