## 3 Test Results and Discussions
### The Effects of BOF slag Contents on the Specim Cooling Interval  
[PERSON] and [PERSON] (2011) established the three zones by the temperature-time curves: initial temperature, cessation temperature, and equilibrium temperature, respectively ([PERSON] and [PERSON], 2011), as can be seen in Figure 4. The initial temperature zone represents the temperature changes from the time the asphalt mixtures leave the plant to the end of the compaction. The mixtures reach a more stable state at the cessation temperature. In addition, the equilibrium temperature indicated that the asphalt temperature could basically be the proper time to be 'open to traffic'. In this study, the temperature-time curves for mixtures containing various BOF slag content are shown in Figures 5-7. Temperatures corresponding to the three inflection points of the curve were defined as the points. From Figure 5, it can be seen that the initial temperature on dense mixtures decreases as the BOF slag content increases. For a dense specimen without BOF slag, the initial temperature was 95\({}^{\circ}\)C; for a specimen with 60% BOF slag, the initial temperatures drops to 90 \({}^{\circ}\)C. This means that the BOF slag in the dense mixtures can store the thermal energy longer. Figure 4: Cooling interval diagram of the asphalt mixture. The cessation and equilibrium temperature increases as the BOF slag content increases. [PERSON] et al. 2000 [37] defined the cessation temperature as the asphalt mixture temperature at which the density of asphalt pavement cannot be improved with additional compaction effort. Based  
Figure 5: Relationship between the temperature intervals and the BOF slag contents (dense). Figure 6: Relationship between the temperature intervals and the BOF slag contents (SMA). Figure 7: Relationship between the temperature intervals and the BOF slag contents (PA). on this concept, for mixtures without and with 100% BOF slag, the cessation temperatures drop to 76 \({}^{\circ}\)C and 86 \({}^{\circ}\)C, respectively. The BOF slag in the dense mixtures could reach stability earlier at a higher temperature than those without BOF slag specimen. For mixtures without and with 60% BOF slag, the equilibrium temperature drops to 70 \({}^{\circ}\)C and 79 \({}^{\circ}\)C, respectively. This phenomenon indicates that the use of BOF slag has a stable nature, even if the equilibrium temperature is higher than the pure, dense specimen, about 9 \({}^{\circ}\)C, and it can be 'open to traffic' on asphalt pavement. From Figure 6, the initial, cessation, and equilibrium temperature on SMA mixtures increase as the BOF slag content increases. The mixture, which is made with a high amount of the coarse particles, forms a coarse aggregate skeleton. This increases the interlocking of the aggregates and provides better stone-to-stone contact, which serves as a load carrying mechanism, and, hence, provides better loading resistance. SMA specimen coarse aggregate particles form a stone-to-stone contact skeleton that can transfer thermal energy and increase all of the temperature zones. Moreover, cessation and equilibrium temperatures of the SMA mixtures were not significantly different. This indicates that asphalt mixtures with BOF slag can be compacted and opening at higher temperatures as compared with those without BOF slag. From Figure 7, the initial, cessation and equilibrium temperature on PA mixtures increase as the BOF slag content increases. A similar trend is also observed for the cooling interval within the SMA mixture. However, the PA mixture had a lower initial temperature interval than the SMA mixture. As mentioned earlier, for the mixtures with 40% and 60% of BOF slag, the VMA values of all the PA mixtures were higher than those of the SMA mixture, and, therefore, contain higher amounts of coarse aggregate ((19, 12.5 and 4.75 mm aggregate size). Asphalt mixtures increase the porosity and contain a higher amount of coarse aggregate, which decreases the thermal conductivity, resulting in a higher temperature.