This study investigates the possibility of utilising bottom slag (BS) waste from landfills, and a carbonation process advantageous for the use of artificial aggregates (AAs) in printed three-dimensional (3D) concrete composites. In general, the main idea of granulated aggregates is to reduce the amount of CO₂ emissions of printed 3D concrete objects (wall). AAs are made from construction materials, both granulated and carbonated. Granules are made from a combination of binder (ordinary Portland cement (OPC), hydrated lime, burnt shale ash (BSA)) and waste material (BS). BS is a waste material left over after the municipal waste burning process in cogeneration power plants. Whole printed 3D concrete composite manufacturing consists of: granulating artificial aggregate, aggregate hardening and sieving (adaptive granulometer), carbonation of AA, mixing 3D concrete, and 3D printing. The granulating and printing processes were analysed for hardening processes, strength results, workability parameters, and physical and mechanical properties. Printings with no granules (reference 3D printed concrete) were compared to 3D printed concretes with 25% and 50% of their natural aggregate replaced with carbonated AA. The results showed that, theoretically, the carbonation process could help to react approximately 126 kg/m³ CO₂ from 1 m³ of granules.

In this research, the results of an experimental study on the use of three alternative components for creating artificial aggregates (AAs) (granules) and their usage in 3D-printed concrete (3DPC) are examined. This study combines AAs made from organic components like hemp shives (HSs), pyrolyzed coal (charcoal), waste/municipal solid waste incinerator bottom slag (BS), and a mix of a reference 3DPC with the aforementioned AAs. Particularly, to enhance these properties to make low-carbon 3DPC, in this research, the potential of using AAs as lightweight aggregates was increased to 14% in terms of the mass of the concrete. Each mix was tested in terms of its printability via a preliminary test in a 3D printing laboratory. For an additional comparison with the aforementioned cases, 3DPC was mixed with unprocessed hemp shives, charcoal, and BS. Furthermore, their strength was measured at 28 days, and lastly, their durability parameters and shrinkage were experimentally investigated. Cross-sections of the fragments were studied under a scanning electron microscope. In this study, we achieved improvements in the mechanical properties of AAs for their development and implementation as an innovative way to reduce carbon in 3DPC.

This study investigates the feasibility of incorporating wood-based waste in cementitious composites for extrusion-based three-dimensional (3D) printing through the production of artificial aggregates. Because lignocellulosic residues can retard cement hydration, wood dust was chemically modified with a calcium nitrate-based accelerator and granulated into aggregates using disc granulation. The resulting aggregates were characterized for mechanical robustness, and their influence on cement hydration and microstructural development was evaluated using X-ray diffraction (XRD) and thermogravimetric/differential scanning calorimetry (TG/DSC). The modified aggregates were then incorporated into 3D printable cementitious mixtures to assess fresh-state properties, printability, and mechanical performance. The accelerator affected hydration by increasing bound water content and altering the development of hydration products. The produced aggregates exhibited sufficient crushing resistance for practical handling. The incorporation of artificial aggregates resulted in reduced compressive and flexural strengths compared to the reference mixture. However, the differences between mechanical properties measured in different loading directions were reduced, indicating a more uniform structural response in printed elements. The findings demonstrate that chemically treated wood-based aggregates can be successfully integrated into 3D printable cementitious systems, offering a promising pathway toward more sustainable construction materials.