Development of 3D Printable Cement-Based Composite Containing Oil Shale Ash

Mortars used in 3D-printing typically contain large amounts of cement and other high-value powders to ensure printability. Consequently, 3D-printed concrete structures have a high carbon footprint. In the Baltic states, power plants utilize oil shale, producing significant amounts of non-biodegradable oil shale ash (OSA). To address these environmental problems, we are aiming to formulate a preblended dry product for extrusion 3D printing which contains oil-shale ash. To assess suitability for the use in cement-based composites, the properties of raw OSA are studied, including particle size distribution, chemical composition, specific surface, reactivity, and shape with SEM. Additionally, the influence on mechanical properties has been studied when substituting reactive powders in a pre-blended mix with oil shale ash in varying quantities. Additionally, workability and buildability of mixtures in fresh state is investigated to determine suitability for 3D printing. The preliminary results have revealed that replacing up to 20% of reactive powders with oil shale ash does not lead to a significant decrease in mechanical strength in the hardened state. Moreover, in the fresh state, substituting up to 20% of reactive powders with OSA enhances workability. Based on findings thus far, OSA is a viable substitute for cement in printable concrete, with the potential to reduce the carbon footprint of printed structures.