Utilization of machine-made sand waste in 3D-printed ecological concrete for artificial reefs

With societal advancements, the use of machine-made sand has become increasingly prevalent. However, its production generates significant waste with limited utility. To address this issue, this study introduces an innovative ecological concrete material with a high substitution rate, examining the feasibility of using machine-made sand waste in concrete for 3D-printed artificial reefs. Experimental results showed that the incorporation ratio of machine-made sand waste could reach 30%. Although this inclusion slightly reduced the concrete's mechanical properties, it achieved a compressive strength exceeding 30 MPa after 28 days of curing, meeting the requirements for artificial reef construction. Additionally, the material demonstrated excellent printability, producing well-formed components with intact appearances. Observations from laboratory fish behavioral studies and field tests in marine environments confirmed that the concrete material did not adversely affect the activity or growth of benthic fish species and exhibited favorable bio-affinity. Furthermore, the carbon emissions associated with this material were significantly lower than those of traditional concrete reef materials. In conclusion, this novel concrete offers significant advantages in terms of mechanical performance, printability, biocompatibility, and carbon emissions, providing essential theoretical and experimental support for the development and promotion of eco-friendly artificial reef materials.