## 3 Results and Analysis  
### Effect of Filler Type and Volume on Moisture Damage Resistance  
Mineral fillers are important factors in asphalt mixtures as they assist in increasing the stiffness of asphalt binder, thus providing more resistance to rutting at high temperatures. However, fillers can also impact asphalt bonding to aggregates, thus increasing the susceptibility to moisture of the asphalt mixtures. A previous study [23] showed that the type of mineral fillers affected moisture damage resistance. However, there has not been studies on the effect of different asphalt music volume on moisture damage resistance. Four types of filler, including limestone, granite, bagasse, and coconut peat were added to the asphalt binder at 20% and 30% by volume of the asphalt mastic. Table 2 shows the values of ITS test on asphalt mixtures with limestone aggregate and different filler contents (i.e., 20% and 30% by volume) for all four filler types in the dry and wet conditions. The results show show that in the dry condition, the values of ITS of 20% filler were in the range of 0.24-0.28 MPa, while the those of 30% filler showed higher strength in the range of 0.27-0.32 MPa for all filler types. Similarly, results show that after the wet conditioning, the ITS values of 20% filler were lower than those of 30% filler for all filler types. Table 3 shows the values of ITS test on asphalt mixtures with granite aggregate and different filler contents (i.e., 20% and 30% by volume) for all four filler types in the dry and wet conditions. The results are different from the limestone aggregate, as the higher content of filler yielded lower values of ITS in the dry condition. Similarly, in the wet condition, the ITS values at higher content (i.e., 30% by volume) of filler were higher than those at lower content (i.e., 20% by volume). Figure 4: A dolly attaches to a Marshall sample. Figure 5: A water bath to control the pull-off tensile strength test sample. To identify the potential effect of filler types on moisture damage resistance, the TSR was calculated as the indicator from the ITS testing. Figure 6 shows the ratio of tensile strength after the wet conditioning of asphalt mixtures with limestone aggregate for all filler types. The results show that the TSR values for both filler contents were above the 0.7, which is a typical specification threshold of minimum tensile strength ratio. The results show that both waste natural materials (i.e., bagasse and coconut peat) can be used as fillers at 20% and 30% by volume for limestone aggregate to resist the moisture damage in asphalt mixture since they showed the values of TSR in range of 0.73-0.89. The results also show that the TSR for the 20% filler gave higher values than those for the 30% filler. In contrast, TSR for granite aggregate present lower values than 0.7 for all fillers as shown in Figure 7. However, using waste natural fillers (i.e., 0.61 and 0.63 for bagasse and coconut peat, respectively) could give higher TSR than that of limestone filler (i.e., 0.59) for 30% filler content. In addition, the results conversely show that the TSR for the 20% filler gave lower values than those for the 30% filler. This indicates that the TSR is dependent on aggregate type and filler content. If the mixture contains limestone aggregate, the moisture damage resistance will pass 0.7 TSR for both filler contents at high traffic volume gradation. However, increasing filler content can give rise to lower TSR. Conversely, it appears that the mixture contains granite aggregate, the moisture damage resistance will not pass 0.7 TSR for both filler contents at high traffic volume gradation. In this study, results preliminarily confirm that bagasse and coconut peat can be used as a filler in a mixture with limestone aggregate at high traffic volume design to resist moisture damage. Further studies are needed to verify the optimum filler contents for all traffic volume designs and establish threshold of filler content for bagasse and coconut peat.