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Abstract
The drainage capacity of porous surface course is one of the most important functional properties of a porous asphalt pavement. The ability to measure this property in the field is highly desirable. However, the flow measurement devices currently used for drainage testing of in-service porous pavements typically uses the time taken to discharge a given volume of water as the basis for assessment and comparison. Such empirical measurements are unsatisfactory, as they cannot be used to determine the actual drainage capacity and the flow properties of the material. Field equipment for non-destructive measurement of the in situ permeability of porous pavement surface materials has been developed. This paper describes the theoretical basis and operation of the equipment. A test on normal porous pavement materials with permeability of the order of lO mm/s takes less than 2 min to complete. A demonstration project was performed to test two pieces of the equipment in a 14 km porous pavement expressway in Singapore. The project investigated The single-equipment reproducibility, and the between-equipment repeatability of test results. It was found that the coefficient of variation of measurements was of the order of 4%, and the results showed very good between-equipment repeatability at the 95% confidence level. The results suggest that the equipment provides a useful tool for expedient field measurement of the in situ permeability of porous pavements.