The mix design method of semi-empirical gold tailings sand UHPC based on the MAA model

The integration of manufactured sand into Ultra-High Performance Concrete (UHPC) remains limited, and the design methodology for UHPC mixes is not yet fully developed. This study proposes a semi-empirical gold tailings sand UHPC mix design method based on the Modified Andreasen and Andersen (MAA) model as an example of bulk solid waste gold tailings sand. This method compensates for the shortcoming of the unknown strength of the formulation when designing the mix using the MAA model. Also, it optimises the semi-empirical method of mix ratio design. The results of the study show that the method can be used to accurately obtain the unit amount of gold tailings sand and the rest of the raw materials in UHPC. Tests conducted on the slump flow, slump flow time, cubic compressive strength, and splitting tensile strength have demonstrated that the workability of the UHPC meets the required specifications, with the formulated mix's compressive strength deviating by less than 5%. At the same time, the gold tailings sand slightly reduce the fluidity of UHPC, while it has a positive effect on the compressive and tensile strengths. The compressive strength of UHPC with 28 days of gold tailings sand is improved by 4.57%, and the tensile strength is improved by 14.77%. In addition, the compressive strength of UHPC with 7 days of gold tailings sand is increased by 16.56% compared with that of the control group, indicating that the incorporation of gold tailings sand effectively improve the early compressive strength of UHPC.