4.1 Summary of Pavement Damage Evaluation
From the technical data collected and the analysis performed, the asphalt pavement damage can be separated into two (2) types, mainly the surface problem associated with the integrity of wearing/binder course and the softening of base course due to water intrusion. The problem wearing and binder courses are not discussed in this report because it requires detailed evaluation by the pavement experts, and this type of problem is limited to some isolated areas in aircraft turning zones at the ends of the runways. The latter problem associated with high water level in the pavement zone is studied to a great extent in this report. A detailed water blockage map was produced primarily from the subsurface drainage condition between the sand blanket and the secondary canals. Forty-six (46) individual pavement blocks were identified based on the confinement of the subgrade sand. The analysis has shown that over half of the pavement areas may have water blockage problem which should be taken seriously by the authority. The water blockage map agrees well with the reported pavement damage areas, therefore the water blockage issue should be taken into account in the pavement evaluation. It can also be concluded that the high water level in the pavement has a predominant effect on the deterioration of asphalt pavement, especially in the low-lying pavement such as in the taxilanes. The damage to the base course layer due to the presence of water from the subgrade sand below is well understood by the engineering professions. It should be emphasized that the degree of asphalt pavement damage will be worsened if there is no immediate lowering of the water level in the pavement zone.