Yasuyuki HONMA
Fundamental study on application of the Bailey aggregate parameters to the Superpave mix design
Osamu TAKAHASHI
Some Japanese pavement researchers have investigated application of Superpave procedure to the domestic mix design process in order to deal with the weak points of the Japanese Marshall method. The Superpave design method is regarded as a more rational and reliable procedure because field densification and its performance are taken into account on the process.
In order to introduce the Superpave into Japanese mix design, a guideline on selection of aggregate blends is required for Japanese pavement engineers, because the Superpave doesn¡Çt have a strict standard on both lower and upper limits for all sieve sizes. This study discussed application of the Bailey aggregate parameters to the Superpave procedure using Japanese local ingredients.The Bailey method was also developed by the US researchers, but a relationship between the Bailey method and the Superpave method is not cleared and recommendable values of the Bailey aggregate parameters haven¡Çt discussed yet.The objective of the study was to obtain findings on the following four questions.
1)Which is recommended a fine-graded mixture or a course-graded mixture? What values are suitable for %CA LUW in order to design a high plastic flow resistance mixture? 2)Which aggregates parameter is the most sensitive for the Superpave design parameters and plastic flow resistance in the other three, namely CA ratio, FAc ratio, and FAf ratio? 3)How do the three aggregate parameters influence to Superpave design parameters and plastic flow resistance interdependently and/or independently? Based on the Superpave requirements, various aggregate gradations were designed by parametrically changing the four Bailey aggregate parameters and each design asphalt content was decided. Plastic flow resistance was evaluated for all the mixtures by carrying out Asphalt Pavement Analyzer tests.
From the evaluation of the results, this study derived the following findings. 1) The mixture having 70% in %CA LUW is excellent for plastic flow resistance and contains enough VMA. 2) New FAc ratio influences the VMA value the most within the three Bailey aggregate parameters. However, all the three aggregate parameters don¡Çt considerably influence plastic flow resistance. 3) When the aggregate parameter is selected with the values close to the lower border or upper border, the mixture cannot meet the VMA requirement and is low plastic flow resistance. Therefore, the intermediate values of the recommended range for the aggregate parameter can give a satisfactory VMA. It is true for all the three aggregate parameter.
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