Development Of Uvioresistant Warm Mix Asphalt

Ultraviolet radiation is strong in plateau area. As a result, it can cause a strong aging effect on substances such as asphalt. Therefore, it is necessary for people to build road that can be prevent from ultraviolet radiation damage in the plateau area in China. And the research of asphalt pavement with anti-ultraviolet radiation is of great practical significance to the road construction for our country or even the world. In high altitude area, the temperature is relatively low, which brings inconvenience to the construction. This paper studies the selection from two warm-mixed agents to improve the workability of asphalt, which will cater to the desire for environmental protection and low energy consumption.A box was made to provide UV environment based on the intensity in plateau area. Black high pressure mercury lamps were used as ultraviolet source. First, the modified asphalt was aged by uv radiation for 4 days. The aged effect caused by uv radiation was studied by normal indicators tests, DSR, BBR and infrared spectrometer. Three uvioresistant agents were mixed in the asphalt sample, and the effects caused by admixture were studied. Second, the bituminous cements were put into the uv box to study their ultraviolet resistant effect. The test procedure, which was provide by Design-Expert software, can be ultized to select the optimal ratio of ultraviolet resistant agents. Finally, the performances of the asphalt sample and the asphalt mixture which influenced by two warm-mixed agents were studied, and we need to decide which one is better.Study found that the ultraviolet aging can improve the viscosity of asphalt. However, there was no obvious effect on changing softening point. Along with the increasing aging time, ultraviolet radiation could increase the complex modulus of asphalt mixture, as well as damaging visco-elastic parts of the material. Meanwhile, ultraviolet aging can reduce the creep rate of asphalt cement and increase creep stiffness, which had an adverse influence on the low temperature cracking resistance. From the results of infrared spectrum experiment, we can see that both the increasing of carbonyl absorption peak area and sulfoxide turbulence indicate the degree of aging positively correlated with uv radiation time.Light screener A increased the softening point of asphalt cement, and enhanced its high temperature stability, viscosity, flow deformation resistance as well as rutting factor. Therefore it has positive effects on high temperature rutting resistance. Screener B is similar to agent A. But the effects are less obvious than screener A. Absorbent played an opposite role to light screeners, which can reduce the softening point and viscosity of asphalt cement. When the dosage of absorbent increased, the rutting factor decreased. At low temperature, screener A and B, with dosage from 1% to 3%, could increase the creep stiffness of asphalt mixture and make it brittle. When the creep stiffness decreases, the absorbent increased the creep rate, which improving the crack resistance of the material. DSR test showed that screener A has a nice uvioresistant effect with 1% dosage at high temperature. When the proportion of screener B reached 3%, the complex modulus curve is close to the data of 4 days aging asphalt. If the dosage of agent B was 1%, the margin of descending modulus was greater than the margin of increased modulus caused by ultraviolet aging. BBR test showed that screener A and B can’t improve low temperature performance of asphalt mixture. What’s more, with the increase of dosage, the creep rate reduced. At the dosage of 2%, the extent of creep stiffness reduced by absorbent has been greater than the one increased by ultraviolet aging.Through the optimal proportioning test procedure designed by Design-Expert software, the final choice of ultraviolet resistant components is:96% SBS modified asphalt,0.8% screener A,3%screener B and 0.2%absorbent. From the contrast tests of mixing agent, we believe that warm-mixed agent Leadcap is more suitable for using in cold area than Sasobit, since Leadcap warm mix asphalt mixture has better crack resistance at low temperature.