Preparation of ultra-high performance concrete containing waste foundry sand and its application in structures

The resourceful recycling of waste foundry sand (WFS) has aroused continued interest. In this research, the feasibility of application of WFS in ultra-high performance concrete (UHPC) beams was explored. Firstly, the material properties of 12 groups UHPC consisting of 4 replacement levels of WFS for aggregate and 3 water-binder (W/B) ratios were tested. Then, the flexural tests on 6 UHPC beams were conducted and the structural response were analysed. Finally, theoretical analysis was performed to guide the design of UHPC beams with WFS. It has been proved that the UHPC beams containing appropriate content of WFS could achieve satisfactory performance. There was an 11.4% and 9.3% improvement of the compressive and tensile strength of UHPC containing 20% WFS with the W/B ratio of 0.18 compared with that without WFS. In addition, the cracking load, yield load and ultimate load of the UHPC beam increased by 25.9%, 23.3% and 12.2%, respectively. Meanwhile, the ductility, stiffness and crack resistance also exhibit a certain degree of enhancement. The average values of the ratios of prediction and test results of cracking moment, flexural capacity and crack width of UHPC beams containing WFS are 0.96, 0.93 and 1.04, respectively, indicating that the equations have satisfactory accuracy.