Preparation of water-quenched manganese slag and fly ash ultrafine mineral admixture and its application in UHPC

In this paper, S95 grade ultrafine mineral admixture (UMA) was prepared by water quenched manganese slag and fly ash 1:1 compound mechanical ball milling to a specific surface area of 714 m2/kg. Its activity index was 86.8% at 7d and 96.3% at 28d. The S95 UMA prepared by ball milling has the characteristics of small particle size, high specific surface and high activity. Mixing with powders of different particle sizes, such as cement and silica fume (SF), is helpful to improve particle gradation, reduce its pore structure and increase its compacting property for ultra-high performance concrete (UHPC) whose raw materials are fine aggregate. UHPC was prepared by using the obtained UMA based on orthogonal test. The effects of different factors on the workability, mechanical properties, hydration heat and microstructure of UHPC were studied. The results show that when the SF content is 10%, the mineral admixture content is 10%, the binder–sand ratio is 1.1, and the water–binder ratio is 0.17, the fluidity of UHPC slurry can reach 261 mm, the compressive strength of 7d and 28d age can reach 128 MPa and 154.6 MPa, respectively. The hydration heat release of cementitious materials in 3d was 139.8 J/g. In terms of solid waste resource utilization, S95 grade UMA prepared by water-quench manganese slag and fly ash can replace 10% SF for the preparation of UHPC. It can not only solve the utilization problem of high added value of water quench manganese slag but also reduce the preparation cost of UHPC to a certain extent.