determination of the optimum asphalt content usually associates the Marshall Index with volumetric parameters for hot mix asphalt (HMA). Because unreasonable volumetric parameters may result in the asphalt content being more or less so that performance of HMA are influenced. Therefore in this paper, relationships between volumetric parameters and the Marshall Index were studied for two kinds of gradations, AC25 and AC13, which for each kind of gradation, according to the orthogonal test method, the pass percentages of aggregate between the each sieve size and the usage of asphalt contents were changed to form 50 sets of asphalt mixtures for the Marshall test and the volumetric parameters experiment. The results show that rank of influence significance of volumetric parameters on the Marshall Index is Gmb and VV, then VMA and last VFA. However, for fine aggregate (AC13) asphalt mixtures, as Gmb increases, all the MS and the FL increase. Meanwhile, as VV increases, the MS and the FL of AC25 asphalt mixtures increase, whereas for AC13 asphalt mixtures the MS decreases but the FL increases. So for proportion design of fine aggregate (AC13) asphalt mixtures, the fine aggregate and the asphalt content must be strictly controlled to meet the VV requirement and to avoid asphalt pavements to become over-densified. In addition, with VMA increases, for course aggregate (AC25) asphalt mixtures, MS and FL increase, but for course aggregate (AC13) asphalt mixtures, MS decreases but FL increases. Otherwise, the influence of VFA on MS and FL could be nearly ignored.
