Sustainable 3D printed clay bricks incorporating coffee waste: Toward circular economy in construction

This study investigates the potential of spent coffee grounds (SCG) as a sustainable additive in the production of 3D-printed clay bricks. To analyze the effect of this incorporation on the physical, thermal, and mechanical properties of the bricks, clay was partially replaced by 3 %, 5 %, 10 %, and 15 % SCG by weight. The parameters evaluated include density, water absorption, porosity, thermal conductivity, and compressive strength, supplemented by structural observations via X-ray tomography. The findings indicate that increasing the SCG content results in enhanced porosity (from 3.30 % to 18.85 %) and diminished density (from 1552 to 1184 kg/m³), culminating in a substantial reduction in thermal conductivity (from 0.45 to 0.20 W/m·K), signifying a 55 % enhancement in insulation properties. However, a gradual decrease in compressive strength was observed (from 33.54 to 12.61 MPa). It is theorized that a 10 % SCG content represents the optimal compromise, making the bricks lighter and improving their thermal performance while maintaining satisfactory mechanical integrity. These results confirm the value of SCG as a renewable resource for developing lighter, more efficient, and environmentally friendly building materials. • Spent coffee grounds (SCG) were used as additives in 3D printed fired clay bricks. • SCG addition induces functional porosity, enhancing thermal insulation properties. • X-ray tomography revealed the evolution of microstructure with SCG content. • A 55 % reduction in thermal conductivity was achieved at 15 wt% SCG addition. • The study supports circular economy by valorizing waste in sustainable bricks.