| Bituminous pavement is well known for its running-comfortable and outstanding performance, fast speed of construction and convenient of maintenance, so bituminous pavement has been widely used in highway construction in our country. With the rapid development of China's national economy, the rapid growth of traffic volume, more and more larger vehicles, serious overloading and canalization traffic volume, so bituminous pavement faced with a severe challenge. The urgent requirement of development transportation demands the surface course of bituminous pavement should be have good operational performance.To meet the requirement of increasingly heavy transportation,great volume of traffic, fast traffic and running-comfortable, the direction of asphalt mixture progress is towards the rough skeleton and coarse aggregate contact with each other interlocking trend. In order to improve the performance of asphalt pavement, extend life and reduce the incidence of early damage, make it better satisfied to meet the traffic demands, some novel type of asphalt mixtures were used in many new expressway . Including SMA, SAC and the Superpave pavement design system which introduced from America, meanwhile, modified asphalt be used or adding fiber into asphalt for increasing the thickness of asphalt membrane, in order to enhance the consistency of asphalt and to improve the anti-fatigue and aging properties.In recent years ,there is a tendency of using dense asphalt in the international ,for enhancing the capability of anti-rut, especially basecourse and roadbase, for example, the hard asphalt with lower Penetration(10/20～15/20mm-1)was used to develop high-modulus asphalt mixture in France.Hard asphalt with lower degree of penetration and higher soften point. it has been used widely in Europe with its advantage of resisting high temperature properties and effectively reducing the thickness of surface. Although hard asphalt has been successfully applied in Europe, especially France, but the climate and transportation conditions are vastly different from our country. Whether the hard asphalt fits to our country environment and what about its properties and performance, are all needed a lot of test to verify. The using of 30# hard asphalt in road in our country is still new, there are few experiences and many problems to be solved. For this reason, we choose 30# hard asphalt and its mixture as the studying object, evaluate the pavement performance by testing the technical index of the 30# hard asphalt and study the component design of hard asphalt mixture according to the stone asphalt concrete composition theory and the calculation method, suggest SAC25 grading, which proved useful to 30# hard asphalt. Compared with the SBS asphalt concrete ,we studied the capability of high, low temperature and water stability of 30# hard asphalt concrete. At the same time, analysis the feasibility and economy of 30# hard asphalt which planned to apply in the lower layer of asphalt pavement ; sum up its construction process by paving the test road. All what we have done will lay foundation to the research and application of hard asphalt in our country.Through a large number of laboratory tests, we determined the penetration, softening point, ductility, viscosity and performance indicators after aging of 30# hard asphalt, analysised its performance of the road. The results indicated that its performance indicators meet the current specification requirements of the A-Level 30# hard asphalt exactly except the ductility in 15℃. Although the ductility in 15℃does not comply with current specification requirements, its equivalent brittle point meet the demands of "Eighth Five " issues; and the results after aging test show that the 30# hard asphalt has good aging properties. The calculation of Penetration, PVN and so on show that the 30# hard asphalt has well temperature sensitivity and a excellent high temperature stability. The component design of 30# hard asphalt mixture adopted SAC grading design method. Considering that 30# hard asphalt will be used for the basecourse of bituminous pavement, we choosed SAC25 as the gradation of 30# hard asphalt , determined two kinds of test gradation by calculation. and got the best asphalt-aggregate ratio by Marshall test in which the void ratio is 4% .we tested the grade by the VCADRF and VCAAC method in the process of designing the Mix component. Results show that grade one is the general framework dense structure, grade two is suspended dense structure and would be chosen according to specific circumstances.The test sample is made according to the best asphalt-aggregate ratio, which is used to test the road performance of 30# hard asphalt. In terms of the main purpose of the study, rutting test, soaking Marshall test , freeze-thaw cycles and low temperature bending test , are the main content, and compared with SBS modified asphalt mixtures for assessing its road performance. The results show that: the dynamic stability of 30# hard asphalt mixture is average over 4000 times/mm, far lager than the standard value of 800times/mm, while its dynamic stability is higher than the same grade modified asphalt mixtures too. So 30# hard asphalts mixtures has excellent high temperature stability. Its application to the base-course can greatly enhance the ability of rutting resistance, thereby prolonging the life of roads. And from low temperature bending test and freeze-thaw cycle test results, 30# hard asphalt mixture has a good ability to resist water damage and its low-temperature properties is acceptable to the base-course of the bituminous pavement.On the basis of 30# hard asphalt and its mixture indoor experiment tests, paved a 1.5 km trial road, summed up the hard asphalt mixture construction method. For the construction of the hard asphalt, the key is the control of temperature, due to the low penetration and the high softening point of hard asphalt ,it has higher mixture and pressure temperature , what make the temperature control not easily. This requires detecting the temperature of each vehicle manufactured asphalt mixture in the course of construction and doing well heat preservation work in the transport process, inspecting rolling temperature according to needed frequency to ensure that the temperature meets the requirements. Meantime also in timely making Marshall specimen and drilling core in site for the testing and quality control. In the construction process not only should be careful about temperature but also be careful attention to rolling procedures and the degree of compaction control. Because SAC25 has a lot of coarse aggregate, its paving should be taken to avoid the process of isolation phenomenon.Conclusion can be made through this textual research : According to the performance indicators and the pavement capability of 30# hard asphalt, using it as the basement of the asphalt pavement is feasible. Through calculating and testing the SAC25 graded asphalt mixture, which has high temperature stability and good water stability, verified that it is completely possible to achieve specification requirement of the base-course of bituminous pavement, and its high temperature properties has little difference compared with SBS modified asphalt indeed. Applying it to the medium or underneath layer of the asphalt pavement can improve the ability of rutting resistance. Consider from the economic aspect, compared with SBS modified asphalt, the hard asphalt can also reduce engineering cost in great quantities.
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