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In the past decade, porous asphalt pavements have gained popularity as a stormwater best management practice because this unique asphalt can reduce spray and splash in wet weather, consequently reducing hydroplaning and increasing visibility. However, despite porous asphalt benefits, there are still some weaknesses, such as short service life than dense-graded asphalt due to its lower durability and strength. Coal ash is one of the most abundant industrial wastes and may be harmful to living things and human life if disposed of wrongly. The combustion of coal in the furnace in the power plant produces coal ash, consisting of fly ash and bottom ash. Hence, in this research, utilizing fly ash (class F) and dry bottom ash as a replacement of mineral filler to reduce the drainage value and improve the strength of porous asphalt mix was investigated. Laboratory specimens were prepared using 50 blows of Marshall Hammer per side by the Marshall mix design method. The bituminous binder used was performance grade PG 76, which complies with AASHTO Standard M320-02. The percentage of binder content in the range of 4.0% - 6.0% in increments of 0.5% was used to determine the Design Binder Content (DBC). The mix with both ashes was found to be 5 per cent of DBC. The DBC value for both mixtures was then used to evaluate the mixtures’ performance, which went through a binder drainage test, and rutting test. The performance results were then compared with the control porous asphalt mix using mineral filler. The control mixture and both modified mixtures show drain down values of 0.3%, 0.262%, and 0.167%, respectively. The replacement of both materials into the control mixture indicates that fly ash and bottom ash could increase the binder’s heat resistance and efficiently retain the binder in the modified mixtures. Meanwhile, after the completion of 8000 cycles in the rutting test, it could be seen that the rut depth measured for the mix with mineral filler was 1.6mm, 1.93mm for the mix with fly ash, and 2.04mm for the mix with bottom ash. The bottom ash mix’s higher rut depth value is likely due to the bottom ash characteristic with higher unburned carbon content, thus decreasing the strength mix. It is concluded that an investigation between both ashes in porous asphalt has the potential for the road industry in the future, leading to sustainable highway development.

High demand of recycling waste materials are able to solve disposal problem which created opportunities for researcher to use it in their product. Waste clay brick dust is one of the material can be improvised to be tested for the performance of porous asphalt pavement towards rutting problem. In this study, crushed dust of clay brick was used in porous asphalt mixture as mineral filler. 15 samples were produced in different proportions (4%, 4.5%, 5%, 5.5% and 6%) of bitumen content and each proportion have three samples. The optimum bitumen content (OBC) obtained was 4.75% for modified and 5.9% for conventional porous asphalt. Rutting Test was then tested to evaluate the performance of porous asphalt after being modified with clay dust and compared with conventional mixture of porous asphalt. Modified mixture showed a slight higher in rutting depth of 2.2 mm compared to the conventional mixture of 1.6 mm. This means that modified mixture is less in rutting strength. However, the drain down test showed that modified samples are more intact between binder and aggregate and able to sustain in high temperature. Further modifications are required to enhance rutting strength for modified mixture.

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