Mix design and characteristics evaluation of an eco-friendly Ultra-High Performance Concrete incorporating recycled coral based materials

This paper addresses the mix design and properties evaluation of an eco-friendly Ultra-High Performance Concrete with recycled coral based materials. The modified Andreasen & Andersen particle packing model is utilized to achieve a densely compacted cementitious matrix. Micro-coral sand and coral sand are used to replace cement and sand, respectively. By adopting the Response Surface Method, the effect of blending micro-coral sand and coral sand on the mechanical properties of the designed UHPC is analyzed, aiming at a maximum use of recycled coral based materials. After that, the individual and interactive effects on the durability, autogenous shrinkage and ecological properties of the designed Ultra-High Performance Concrete are evaluated. The results show that the addition of individual recycled coral based materials can improve the workability and reduce the autogenous shrinkage of Ultra-High Performance Concrete without decreasing the durability of Ultra-High Performance Concrete. Compared to the mixture with micro-coral sand, the one with coral sand has less autogenous shrinkage and better durability. Moreover, the designed Ultra-High Performance Concrete with 15% micro-coral sand and 30% coral sand together show the best properties in this study. Additionally, the ecological evaluation demonstrates that the designed Ultra-High Performance Concrete with recycled coral based materials has relatively low environmental impact, which is promising to generate a cleaner product in the near future.