Study on properties of recycled aggregates made from existing marine structures and performance of marine recycled concrete

In order to promote the recycling of concrete from existing marine structures and the sustainable development of the construction industry, the waste concrete members were collected from Ningbo and Zhoushan in Zhejiang Province. The compressive strength and free chloride ion content were tested. The pore structure of specimens was analyzed by mercury intrusion method. Then the concrete was crushed into recycled coarse aggregates and recycled fine aggregates. The physical and mechanical properties, as well as particle morphological characteristics were comprehensively studied. Moreover, the marine recycled concrete was prepared using the simulated seawater and recycled aggregates. The compressive strength and splitting tensile strength were tested. The microstructure and composition were analyzed by scanning electron microscope and X-ray diffraction. The results show that the macro and micro performance of the existing marine concrete is rather discrete due to the influence of local environment. The worse the performance of the existing marine concrete, the worse the qualities of the recycled aggregates, which are characterized by lower apparent density, higher water absorption and higher crushing index. Even if the replacement rates of the recycled coarse aggregates and recycled fine aggregates are up to 100%, the strength grade of the marine recycled concretes is possible to reach C40-C45. Due to that most of the raw materials are able to be obtained locally, there're potential environmental and economic benefits to prepare marine recycled concrete. © 2021, Editorial Office of Journal of Building Structures. All right reserved.