STATE-OF-THE-ART OF RECYCLED MIXED CONCRETE (RMC) AND COMPOSITE STRUCTURAL MEMBERS MADE OF RMC

A mixture of fresh concrete (FC) and demolished concrete blocks (DCBs) with a distinctly larger size of about 50 mm~400 mm is called recycled mixed concrete (RMC). In comparison with traditional recycled aggregate concrete, RMC has the following advantages: 1) the energy consumption associated with crushing of waste concrete is reduced by 40%~60%; and 2) cement consumption is reduced by about 30%. Structural members composed of RMC and steel sections include beams, columns, slabs, walls and connections. This paper presents a simple review of the studies conducted by the authors and their group on RMC and the aforementioned composite members in recent years, discusses the construction technologies of the composite members, and suggests the development orientations of RMC and the composite members. From the current studies, it can be concluded that: 1) there are double size effects in RMC and the scope of application of DCBs with lower strength may be remarkably expanded by mixing them with high-strength FC; 2) the fundamental mechanical performance, seismic properties, fire resistance, and creep behaviors of the composite members cast with RMC are generally similar to those of the counterpart members cast with FC alone; and 3) improving the construction technologies in situ is the key to large-scale practical application of RMC.