Synergetic recycling of recycled concrete aggregate and waste mussel shell in concrete: Mechanical properties, durability and microstructure

The sustainable management of solid wastes and the development of alternative construction materials are essential issues that have plagued urban green development, especially for some resource-constrained island countries or cities. The efficient resource utilization of solid wastes as the alternative of construction materials during the concrete production might provide a potentially promising solution to meet these challenges. In this study, the effects of the combined utilization of mussel shell aggregate (MSA) and recycled concrete aggregate (RCA) on mechanical, durability and microstructural properties of mussel shell-recycled aggregate concrete (MS -RAC) were investigated. The results show that the increased MSA replacement rate exhibited a more negative influence on the compressive strength and splitting tensile strength of MS-RAC than the increased RCA replacement rate. The combined utilization of MSA and RCA resulted in a lower steel corrosion resistance (i.e. more negative open circuit potential, higher corrosion current density, and higher corrosion rate) during the chloride attacks. These could be attributed to the higher debonding rate of MSA-mortar interface and more complicated ITZs due to the incorporation of MSA and RCA. Furthermore, compared with the RCA, the incor-poration of MSA resulted in more macropores and an increased porosity in MS-RAC, thereby significantly weakening the mechanical and durability properties of concrete.