• International Journal of Highway Engineering
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• v.9 no.1 s.31
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• pp.57-67
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• 2007

Many researches have recently discussed about the film thickness as a good substitute or supplement for VMA or other volumetric criteria in the design procedure. Some researchers have not only proposed the specific number for the recommended film thickness, but also introduced the new calculation procedures or concepts. Each model (index model and the virtual model) has its own advantages and disadvantages in terms of the ability to account for the volumetric properties of the mixture. In this paper, the modified virtual model was proposed to combine advantages from both models. However, it cannot be disregarded the way to determine the appropriate particle shape factors for different sources and sizes of aggregates. In order to evaluate the different calculation methods, mixtures with two aggregate sources and eight gradations were designed based on the dominant aggregate size range (DASR) porosity concept. Superpave indirect tensile test (IDT) and asphalt pavement analyzer (AEA) test were used to describe the performance of mixtures. Test results indicated that the virtual model, which is the same to the modified virtual model for sphere 1:1 case, is better than the conventional standard model to define the range of the film thickness to have better performance of asphalt mixtures.