| 요약2 |
This study proposes a spalling mechanism based on the results of a fire resistance test of high strength concrete considering influential factors of spalling occurrence. The factors considered in this test are water to binder ratio (W/B), mineral admixture, air content, moisture content, aggregate existence and casting method. Totally fourteen specimens are set up with varying 2 or 3 other factors of each experimental factor. 0.05 vol.% of polypropylene fiber is added in all specimens, except for the centrifugal casting specimens. This fiber content is decided to compare the spalling appearance effectively. The results of the fire test showed that the specimen using coarse aggregate as a concrete condition exhibited the falling-off phenomena on surface area, while using only fine aggregate as a mortar condition indicated cross sectional spalling occurrence. Interestingly, one of the centrifugal casting specimens was protected from spalling. It was also found that spalling was not observed in those specimens without silica fume, containing 0% of moisture and having 10±0.5% of air. In this study, the hypothesis of vapor movement with time progressive at elevated temperature is suggested and then ultimately a new mechanism regarding the particular spalling phenomena, which has not been explained with previous studies, is proposed. |