Asphalt Mix Design And Performance Evaluation In Perennially Frozen Soil Area

Perennial frozen soil area is 35 106km2 approximately in all over the world, and 5 percent of total areas distributes on Qinghai-Tibet ALTIPLANO in China. With the development of the west of china's economy quickly, asphalt concrete pavement is constructed widely in Perennial frozen soil area. But because of the restriction of climate, environment, material providing and construct condition, pavement's disease occurs generally, it's necessary to research a system of asphalt binder's choosing, asphalt-mix-design, pavement performance evaluation adapt to this area.Firstly, it is principal to choose the appropriate asphalt binder in the asphalt-mix design. Double indexes seem as penetration and Toughness ratio was adopted in choosing. Toughness ratio mustn't be less than 5.0 when the penetration is great than 120 but less than 200, then it need be validated through other traditional technique index.Secondly, in this area the freezing index exceed 2600℃.day, daily mean temperature difference reach 18～20℃,extreme low temperature is under -40℃sometimes, so unconventionality (45℃) Marshall test, Freezing-thawing circle Cantabro test, Freezing thawing circle bending and fatigue test,45℃rut formation test is introduced in performance evaluation firstly to simulating the local condition properly. At the same time the energy theory and"toughness"index in the cracking mechanism is applied in this paper.Finally, The mixture sample was molded in 7 kinds of different asphalt aggregate ratio from 4.5% to 7.5%,it's found that asphalt binder and void ratio is the most sensitive factors to the performance of asphalt mixture in this area through the research of cracking resistance, freezing resistance, fatigue resistance performance, and optimal void ratio ought to be from 1.5% to 3.0%,Marshall stability in 45℃must be above 8.5KN. it's found that the loss difference exceed 1.0% impossibly when asphalt aggregate ratio is above 6.0%, and when asphalt aggregate ratio is less than 7.0%, dynamic- stability in 45℃will increase from 1000 times per millimeter, so loss difference that is not exceed 1.0% and dynamic- stability in 45℃that isn't less than 1000 times per millimeter ought to be he key index in the ajustion of graduation and asphalt aggregate ratio.