Preparation of Recycled and Multi-Recycled Coarse Aggregates Concrete with the Vibration Mixing Process

The reuse of construction and demolition waste has become vitally important because of the requirements of environmental protection and sustainable development. The vibration mixing process is a new technology and novel method that improves the performance of concrete by optimizing the mixing process without changing constituents. This study discusses the 100% recycled and multi-recycled coarse aggregates concrete using the vibration mixing process and investigates the fresh and hardened properties. The results show that the recycled and multi-recycled concrete using the vibration mixing process experienced obviously higher compressive strength than that of non-vibration mixing process. At 120 days, the compressive strength of all mixtures surpassed the target strength (40 MPa), except for the multi-recycled concrete with the non-vibration mixing process. More importantly, the compressive strength of the recycled and multi-recycled concrete using vibration mixing was larger than the previous-generation concrete using non-vibration mixing. Another interesting finding was that the coefficient of variation of compressive strength using vibration mixing was smaller and the concrete quality was better and more stable. The splitting tensile strength of recycled and multi-recycled concrete was also investigated and discussed. In addition, the results of t-tests show that vibration mixing has a significant influence on the compressive and splitting tensile strength of recycled and multi-recycled concrete. It is expected that the vibration mixing process could be a more efficient way to help the wide application of recycled and multi-recycled concrete.