| 요약2 |
As the demand of super tall buildings is increasing in downtown areas, the practical use of ultra high strenth concrete over 80 MPa tends to be also increasing. Therefore, the importance of using pre-mix cement becomes higher as the demend of admixtures, which improves the workability, durability and economic feasibility of ultra high strength concrete, is increasing. The introduction of the pre-mix cement would be useful to reduce the number of silos and mixing time and raise the efficiency of production. The existing cement mixer plants can produce it with the existing facilities and hold a economically dominant position in the industry. Silica fume, which is considered to be an essential material in ultra high strength concrete, consisting of ultra fine particles and tending to lump when mixing with concrete since its dispersibility is low, does not improve the concrete quality even though it is expensive. However, pre-mix cement shall increase the flowability, strength, and durability of concrete since ultra fine particle admixture such as silica fume is dispersed enough in binders. The study compares and analyzes the fundamental properties of pre-mix cement by changing the method of mixing, kind of binders and kind of silica fume in order to understand the influence of the pre-mixed cement on ultra high strength concrete. The study shows that produce pre-mix cement by mixing blast-furnace slag powder and silica fume B in OPC, and then apply it to ultra high strength concrete, flowability shall be improved, setting shall be speeded up, and strength shall be developed. |