The authors study a new type of UHPFRC that is curable on construction site. This paper represents a new finding about an effect of the combined use of steel fibers with different lengths to the compressive and bending strengths, achieved from experiments in which specimens are made with UHPFRC that is curable on construction site. The results showed that the specimens made of UHPFRC with combined use of fibers with 6mm and 13mm in length had better bending strength, in comparison to the specimens with a single use in length of the fiber, in which all the volume fractions of fiber were the same （Vf＝2.0％）. But the compressive strength of the specimen was confirmed to be the same even when the length of fiber was single or combined. It was found that the high strength specimen with two lengths of the fiber had a larger number of the fiber that appeared on the cut surface than the specimens with a single length use of the fiber. Then, it is suggested that the number of the fiber had a positive effect on bending strength. Also, an experimental result is shown about the key issues of the binder component of UHPFRC for searching a best mixture, achieved from the specimens made of different ratio of blast furnace slag fine powder and gypsum in the binder component.
