The blast furnace slag was recently used to develop new geological improvement hardener (super fine cement) (SFC) for soil improvement purpose at Taiwan. Advantages of the super fine cement include better waterresistant and improved soil strength resulted from a wellgraded grain size distribution. Moreover, because the SFC is recycled from the manufacture process of iron, not only the price of the SFC is very compatible with other Portland cement but also recycling slag is a typical case of waste reduction.
    In this paper, the authors will first present the material properties of the SFC. Three cases will then be presented to describe the applications of this new cement at public works. Finally, performance of the SFC would be summarized as conclusions of this paper.