Design Of Interlocking Skeleton Asphalt Mixture

Based on the composites structure of asphalt mixtures, strength models are suggested from mechanics view. Those models primly explain the strength mechanism of interlocking skeleton asphalt mixture.Through the analysis on packing and filling characteristics of the sphere particles, the primary control sieve is calculated to be 0.277D in the three-dimension models based on the filling theory. For interlocking skeleton asphalt mixture, theoretical formulae of the dosage of coarse aggregates and the dosage of fine aggregates and fillers are presented in terms of the different frame effects and filling actions of coarse and fine aggregates. The dosage of coarse aggregates of twenty aggregate gradations is 72.5% by the theoretical formulae, which is in good agreement with others' studies.Referencing the formulae of SAC aggregate gradations suggested by Sha Qinglin academician, coarse aggregate in the asphalt mixture is regarded as a whole research object and fine aggregate and fillers a whole research object. The aggregate gradations of interlocking skeleton asphalt mixture are researched based on the Fuller theory and fractal theory and the formulae of coarse aggregate gradation and fine aggregate and fillers gradation are respectively obtained. When 3-XC=nC and 3-XF=nF, the formulae obtained from the two different methods are same, but their significance are different. This testifies the feasibility of the models.Regarding fine aggregate in the asphalt mixture as a whole research object, fractal dimensions range of the samples were obtained by linear regression and listed as AC 13 is 2.43～2.56, Sup13 is 2.28～2.54, SMA13 is 2.66～2.88 and SAC13 is 2.54～2.73, through analyzing the fine aggregate gradation scales from Standards. In some published literatures, coarse aggregates and fine aggregates were investigated integrally, however, the gradations types were neglected sometimes. In the dense gradation mixture, there are little differences between fractal dimensions of the coarse and fine aggregates but it makes sense for skeleton asphalt mixture. For the asphalt mixtures with skeleton structure, coarse aggregates gradations are designed to form skeleton structure but fine aggregates gradations designed to fill the voids formed by coarse aggregates. The objectives are different, therefore their fractal dimensions would be different. It is inappropriate to investigate the coarse and fine aggregates in a skeleton asphalt mixture by the same method.Twenty varied aggregate gradations are tested with VCADRF method and the four coarse aggregate gradations are tested with crush testing method. The results of two methods are in good agreement, which proves that coarse aggregates form the skeleton structure. In the optimum asphalt content design, skeleton structure function of the coarse aggregates in the interlocking skeleton asphalt mixture is not adequately embodied under the Marshall load, so the compressive strength and tensile strength are introduced into Marshall method. The optimum asphalt content determined by the two methods are slightly different for suspending-dense asphalt mixtures but it makes sense for skeleton structure asphalt mixtures. It is shown that the strength performance of interlocking skeleton asphalt mixture can be adequately embodied and the method is applicable. Moreover, the adoption of the two mechanical parameters lays a foundation for the realization pavement structural and material design incorporating.By analyzing the compressive strength, tensile strength, calculated values of shear strength, high temperature performance, low temperature performance and moisture susceptibility of interlocking skeleton asphalt mixture, the value of nC is recommended as 0.4～0.6 and the value of nF is 0.30～0.35. In other words, the fractal dimensions of coarse aggregates Xc is 2.4～2.6 and the fractal dimensions of fine aggregates XF is 2.65～2.70.