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Porous asphalt mixture is one of the alternative solutions to increase pervious surface area due to urbanization. The uniqueness of porous asphalt surface textures and internal structures allows the mixture to become a temporary storm-water retention and capable to channel excessive storm water. However, one of the major problems that affect the performance of porous asphalt mixtures is the clogging. Therefore, this study aims to determine the effect of clogging towards the permeability of porous asphalt. A total of 30 gyratory compacted samples were fabricated according to aggregate gradation recommended by Malaysia Public Works Department. The clogging materials were collected from two different location, residential area and major highway. The composition and characteristics of the clogging materials were investigated using Plastic Limit, Liquid Limit and Scanning Electron Microscope (SEM). The permeability test was conducted to investigate the permeability rate of the compacted samples based on different clogging material types, clogging concentrations and clogging cycles. In addition, the compacted samples were scanned using X-ray Computed Tomography to obtain the air voids distribution throughout the samples for comparison. It was found that higher concentration of clogging materials and clogging cycles reduced the rate of permeability. Clogging material collected from residential area has higher tendency to clog the void spaces compared to the one obtained from highway.

The open structure of porous asphalt mix influences its strength and durability against air, water and clogging materials. These factors cause loss of adhesion between binder-aggregate interface and loss of cohesion within the binder film.  This could lead to stripping problem which contribute to premature failures as well as deterioration in the performance and service life of porous asphalt. Therefore, this study is aimed to evaluate the potential of diatomite as anti-stripping additives in porous asphalt and compared with hydrated lime and Ordinary Portland Cement (OPC). Field Emission Scanning Electron Microscopy (SEM) test and Energy Dispersive X-ray Spectroscopy analysis (EDX) were conducted to investigate the microstructure and chemical composition of the anti-stripping additives. A number of gyratory compacted samples of porous asphalt mixture with Malaysian gradation were prepared. Each sample was incorporated with 2% of anti-stripping additives as filler then mixed with polymer modified bitumen of PG76. The samples were measured for air voids content, permeability rate, resilient modulus and abrasion loss. The results indicate that samples prepared with hydrated lime show higher permeability rate and lower abrasion loss compared to samples with OPC and diatomite. However, the samples prepared with diatomite show enhanced resilient modulus compared to those with hydrated lime and OPC.

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