An innovative and efficient multi-generation recycling system for waste concrete subjected to freeze-thaw environment: A theory model and case study

Abstract

The existing researches on the recycled aggregate concrete (RAC) mainly focus on the recycling of waste concrete used in atmospheric environment, while the ones on the recycling of waste concrete subjected to complex environments are seldom reported. Reusing waste concrete in freeze-thaw (F-T) environment relates to the multi-generation recycling system of “high performance parent concrete-waste concrete-recycled aggregates (RAs)-next generation of recycled high-performance concrete (RHPC)-next generation of RAs”. The efficient operation and sustainability of such recycling system depends on not only the performances of concrete, but also environmental load and economic benefits. The optimal balance between performance, environmental load and economic benefits for recycling waste concrete in F-T environment is generally affected by the performance of parent concrete and quality of RAs in the recycling system. Based on the theories of the emergy analysis and life cycle cost of structure, a sustainable design theory model of this innovative recycling system is proposed. In this model, high performance concrete (HPC) or RHPC is chosen as parent concrete and the performances of middle and low-quality RAs are improved by carbonation treatment method to gain high-quality RAs. The feasibility of the theoretical model is verified by the emergy analysis of the data of three-generation RAC, which provides a theoretical basis for the frost resistance quantitative design of multi-generation recycled concrete.