Design Of Material Composition And Investigation Into Performance Of Asphalt Pavement On Longitudinal Slope

With economic development, freeway blossoms quickly. In future program, the emphasis of highway construction will transfer to western and mountainous areas. An important characteristic of transportation in our country is over loading, which leads to early destruction of pavement especially on longitudinal slopes because of vehicle accelerating and decreased velocity.Theoretically, the reasons were investigated why asphalt pavement on longitudinal slope is destroyed. It is analyzed from four aspects. The first one is the equivalent quality between time and temperature of asphalt mixture. The second one is the distribution and variation of maximum stress of asphalt pavement on longitudinal slope using FEM (Finite Element Method). Relationships between different kinds of stress and external factors have been obtained by FEM., which can illustrate the mechanism of destruction of asphalt pavement on longitudinal slope. Results show that longitudinal stress, shearing stress on horizontal section increase obviously when vehicle accelerates and slope angle exists. Moreover, overload and heavy load, as well as low velocity will do severe damages to asphalt pavement. The third one is the mechanics between tire and pavement during vehicle running. The fourth one is the relationship between vehicle velocity and the length of slope, as well as the angle. Basing on what discussed above, the model of rutting was established. Then a design method of Skeleton Dense Asphalt Concrete which can be applied to longitudinal slopes was elicited.Different from conventional design methods, it avoids making lots of specimens and complex volumetric properties experiments. Coarse aggregates were firstly divided into three sizes according to the definition of critical sieve in Chinese Specification JTG F40-2004"Technical Specifications for Construction of Highway Asphalt Pavements" , and then dry-rodded tests were done grade by grade to determine the optimal skeleton. Referring to pertinent theory to calculate asphalt content, assuming that fine aggregate, mineral filler and the binder can completely fill the voids of coarse aggregates, deciding a design voids and a proper filler binder ratio, combining to the sieving results of given aggregates, the gradation of skeletal dense structure for asphalt concrete can be obtained directly through calculation. Bychanging temperature, load, angle of slope and vehicle velocity, dynamic stability tests were executed, including saturated and full-scale conditions. All the tests testified that this Skeleton Dense Asphalt Concrete shows excellent pavement performances, such as rutting resistance and anti-skid. Compared with SMA (Stone Mastic Asphalt), the dynamic stability value of SDAC is 8886 timesmm"1 and that of SMA is 7181 timesmm"1. After specimens being freeze-thawed for three times, the values of dynamic stability correspondingly turn into 3230 times-mm'1and 4405 timesmm"1. Additionally, the numerical value of swing of SDAC is 70BPN with that of SMA 72BPN. Similarly, surface structure depths of them are respectively 0.91mm and 1.10mm. Though SDAC is inferior to SMA to a certain extent, it causes less expense and benefits construction.