| In recent years, with the rapid development of our national economy the investment devoted into the highway transportation construction has also been increasing year by year. Simultaneously, the form of the surface course grading that is applied in the highway asphalt pavement in our country goes towards the diversified form from one. Currently, AC, AK, SMA and SUP etc. are commonly used in highway surface course grading in our country. But the application of the grading mentioned above all has some problems more or less. For example, although the denseness of AC grading is very good, the ability of high temperature distortion and skid-resisting capability is bad (especially in raining days). This can easily cause that the brake force is deficient and consequently lead to traffic accidents. Although AK grading has better skid-resisting capability and anti-rutting, it has big air void and bad durability. Therefore, the research which meets the requirements that can make vehicle quickly, safely and comfortably run and solve the contradiction of denseness and skid-resisting capability of asphalt pavement in the premise of good pavement performance has become a popular topic in home and abroad nowadays.The problem how to reduce engineering cost should be taken into consideration when resolving the contradiction. SMA is applied in many highways in our country. Although it has characteristics of good denseness and big structural depth, the investigation shows the phenomenon of isolation and asphalt floating is very serious. Moreover, higher asphalt content of SMA increases the engineering cost. The research result of SHRP SUP also has characteristic of solving the contradiction, but the price of equipments-SGC is high. So it is difficult to be applied extensively in domestic currently. Therefore, the application of SMA and SUP still need to be further studied.There are a lot of factors influencing pavement skid resistance condition. Among them there are two critical factors. One is microtexture that is determined by polished stone value and another is macrotexture composed of coarse aggregate void together. The paper proceeds with the original material of asphalt mixture and makes aggregate polished stone value definite. Consequently, the microtexture influence factor of pavement skid resistance is resolved. Secondly, the grading is optimized in order to increase pavement macroscopical coarseness. The paper refers to the grading theory the domestic and international, such as n method, i method and bailey method etc. Finally, SAC design method is selected in the paper.Firstly, the primal grading is calculated and then the VCADRF and VCAAC test method is used to check and adjust the aggregate grading. Finally, SAC grading that meets the request is determined. SAC design method is very novel so that three different structure types grading are selected to make comparison and analyzed with the grading AC,SMA and SUP. According to the specification request, the marshall test, high temperature stability test, low temperature crack test, water stability test, skid-resistant test and water permeability test are carried out.The indoor test results indicate: Firstly, different grading pavement performance and skid-resisting capability test results have some rules. High temperature performance and the same type grading dynamical stability increase along with the increase of content of coarse aggregate. The filler-asphalt ratio and the dynamic stability of asphalt mixture have a good correlation. The greater is filler-asphalt ratio the greater is the dynamic stability. Simple shear parameters and 70 asphalt specimen dynamic stability test results show that dynamic stability and the internal friction angle also have a good correlation.For the coarse aggregate with the greater water absorption, the more of the coarse aggregate in asphalt mixture the worse is low temperature crack resistance. There is good correlation between low temperature performances with filler-asphalt ratio. The greater is filler-asphalt ratio, the smaller is the ultimate bending strain. For the asphalt mixture with different filler and the same grading, the water stability performance of asphalt mixture with cement as filler is better than that with filler as filler. For the skid resistance performance, structure depth and content of coarse aggregate have a good correlation. The greater is coarse aggregate the greater is structure depth. For the regulation of friction factor, the greater is coarse aggregate the smaller is friction drag of asphalt mixture. Secondly, SMA and SAC have better rutting and stronger anti-shear capacity, better water stability and strong anti-permeability. In view of skid resistance, structure depth of SAC and SMA is bigger, and the decay is slowly along with the increase of wheel hours of operation. Thirdly, gyratory compactors with different types are used to validate asphalt mixture of seven different grading. The test results of SGC show that degree of compaction of SAC and SMA is not more than 98% in the largest number of rotating, which can meet the design requirements. Test results of GTM show that GSF of SAC is the highest and shear-bearing capacity is the strongest. Considering Pavement performance, skid resistance, construction process, construction cost (asphalt content of SMA is higher) and other factors systematically, SAC is regarded as the final surface course of asphalt pavement.Target mixture ratio and productive mixture ratio are designed according to indoor designing mixture ratio of SAC and test results of raw materials. In September, 2005, SAC test sections are settled by task group in Qingdao direction 560+958~558+748 (long 2210m) and YinChuan direction 558+748~560+455 (long 1707m) of QingYin highway. During the course, asphalt mixture is sampled,tested and analyzed.Task group test pavement performance carried out the test in July, October and December, 2006 respectively after test road is paved. Data show:Firstly, SAC has characteristics of framework denseness and wearing capacity. Asphalt pavement SAC has greater structure depth and friction coefficient after it is open to traffic. During the course in use, the variation rules are the same. Test results don,t reduce at all times but increase first and decrease afterwards along with time increasing. Secondly, test results of rutting throughout test road completely meet requirement in specification and the pavement roughness is good. Thirdly, in the case that road is not damaged, many targets of asphalt pavement such as spot air void and degree of compaction can be gained by using anuclear density machine. A good correlation between anuclear density and standard density is found. And 1.07 is regarded as their ratio. Fourthly, the methods of "laser method", laser inertial high-speed pavement roughness evaluated system-LIPRES and automatically test evaluated system- APRES are used to test the pavement performance. The methods mentioned above have characteristics of rapidity and high accuracy.The conclusions obtained from this paper will accumulate precious experience for the research of asphalt pavement skid-resistant technology. |
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