To avoid the disadvantages caused by using silica fume, by using superfine cement (SC) to substitute silica fume, a new kind of ultra high performance concrete (SC-UHPC) was prepared and introduced. The influence of component types and dosages on the mechanical properties of SC-UHPC was investigated. The results show that 40% ground granulated blast furnace slag (GGBFS) or 10% fly ash (FA) & 30% GGBFS replacing SC are the most appropriate proportions to get high strength with satisfied workability and low cost. A suitable amount of defoaming agent (DA) in superplasticizer (SP) effectively reduced the void ratio in the UHPC. To optimize the strength and fluidity, the rational natural sand distribution with lowest clay particles amount can be used. The small sized steel fibers added into the mixture effectively improved the flexural behavior of SC-UHPC. Multiple nonlinear analysis show that, with sufficient calcium silicate hydrate (C-S-H gel) and enough mixture fluidity, the compressive strength of UHPC is closely related to the water to binder ratio and void ratio, and increases linearly with the incremental fiber amount. Microstructure analysis proved that the microstructure of SC-UHPC has ultra high density and homogeneity.
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