Development of a sustainable alkali activated ultra-high performance concrete (A-UHPC) incorporating recycled concrete fines

This study assesses the properties of alkali activated ultra-high performance concrete (A-UHPC) prepared by using recycled concrete fines (RCF) to replace mineral powder in cementitious ma-terials. To be specific, firstly, an optimized combination of low carbon cementitious mixture and aggregates skeleton is designed based on particle dense packing model. Then, the RCF is partly employed and its effect on the hydration kinetics and microstructure development of A-UHPC are tested. The results show that the A-UHPC can exhibit excellent fresh and hardened properties when the water-binder ratio range is 0.29-0.27 and the RCF content is 10-30%. In addition, under the same water-binder ratio and RCF content, the compressive strength of A-UHPC is about 120 MPa. In addition, the carbon emission of A-UHPC prepared in this paper is only 75% of that of ordinary alkali activated ultra-high performance concrete. In general, the newly developed A-UHPC in this study can effectively reuse the recycled fines from waste concrete and provide a new building material with advanced properties, which is in line with sustainable development and low carbon management.