Test Study Of The 30～# Hard Grade Asphalt Used For Mid Or Lower Surface Layer Of Asphalt Pavement

The quick growth of our national economy brings of the phenomenon such as high speed development of traffic volume, more larger vehicle, overload severity and the highway channelization etc.all make the asphalt road of our country in every aspect face rigorous of test, so that the original material (asphalt and aggregate) of asphalt pavement and the function of asphalt mixture all put forward higher of request. As one of the important component of asphalt mixture, the property of asphalt has direct influence on the performance of asphalt mixture and , its price is also direct decision in the meantime the engineering price of asphalt road .In fact, currently the penetration of asphalt used for asphalt pavement in our country go into the degree be partial to big, regardless at south, north, even in the northeast region all appeared severity of rutting .One of the reason to product rutting of asphalt pavement in summer is that the asphalt used for the mid or lower surface layer be partial to soft , for this a lot of freeway used modified asphalt even for the mid or lower surface layer of asphalt pavement ,biggest increment the construction cost of highway .To improve the high temperature stability of the mid or lower surface layer of asphalt pavement , first should choose a good gradation , make asphalt mixture to form framework dense structure ;On the other hand should raise the viscosity of the using asphalt, choose to use hard grade asphalt which has lower penetration is a path into the degree.The hard grade asphalt is a kind of low mark asphalt of heavy traffic, is appear in at the earliest stage 20 century 80's of France, in the domestic main is 30# asphalt which penetration is between 20～40(0.1 mm) .The hard grade asphalt in abroad especially Europe got extensive of application, in abroad a great deal of research and practice all show, hard grade asphalt and its mixture have good high-temperature performance, adoption of it can improve the anti-rutting function of pavement, extend the service life of road combine reduce thin road thickness. Along with our country some asphalt factory produce technique level of exaltation, already ability produce good quality and property stability hard asphalt, the study of hard asphalt by some domestic road worker also increase day by day currently, some experiment research result also indicate hard asphalt and it mixture have good development foreground. Hard grade asphalt and its bituminous concrete application at the asphalt road mid or lower surface layer, in the function and economy are all have its advantage, as to its research also have importance actual meaning.Though the hard grade asphalt application in abroad has obtained very big of success, research also show it has good performance, after all weather condition and actual circumstance in our country have very big difference with abroad , domestic of hard quality asphalt and abroad in the oil source and produce craft etc. all have dissimilarity, and the research and application to hard asphalt and its mixture in our country is still little, the hard asphalt still belongs to new material in the road engineering of our country , theory foundation and practice experience all very lack. To using hard grade asphalt in our country , it is very important to study domestic hard grade asphalt overall and systematically according to the special conditions of our country. Therefore this text with domestic 30# hard grade asphalt for research object, using it in the mid or lower surface layer of asphalt pavement, research the road use function of 30# hard asphalt and its mixture systematically , main include the following several aspect contents:(1) Study on the road use performance of 30# hard grade asphalt .Usage normal regulations experiment method and SHRP asphalt test method be overall measurement 30# hard asphalt of each item technique index sign, assurance PG grade, the relationship of viscosity and temperature and construction temperature , according to domestic and international of the index sign system of the asphalt technique and to the technique of 30# asphalt request, system analysis 30# hard grade asphalt of each item technique function.(2) Research of the component ratio design method of Medium or underneath layer 30# hard grade asphalt mixture .Based on the summary of domestic and international gradation theory and gradation form, consideration the request of the mid or lower layer of asphalt pavement ,look for suitable component ratio design method of asphalt mixture, put forward the component ratio of 30# hard grade asphalt mixture be applicable to the mid or lower layer of asphalt pavement, and through the road use function experiment further argument its feasibility used for the mid or lower layer of asphalt pavement. (3) Compaction study of 30# hard grade asphalt mixture .Study and research the compaction method and compaction characteristic of 30# hard asphalt mixture , ask for help from SGC gyratory to analyze its compaction mechanism , investigate the influence of difference compaction method to its performance, and compare with the spot compaction result compare, put forward the suitable compaction method of 30# hard grade asphalt mixture.(4) The indirect tension test study of 30# hard grade asphalt mixture. Using the England Cooper multi-function asphalt material experiment machine study the dynamic indirect tension stiffness of 30# hard grade asphalt mixture ,announce to public its dynamic state mechanics function, research it main impact factor.(5) Study on the creep characteristic of 30# hard grade asphalt mixture. Based on the theories and methods of visco-elastic mechanics, using MTS experiment machine through static and dynamic load creep test at 40℃and bending creep test at 0℃to study the visco-elastic property of 30# hard asphalt mixture ,use rheological model to regress its parameter, thus further analyze and argue its high and low temperature performance.(6) The application study of 30# hard grade asphalt. On the spot using 30# hard asphalt mixture build experiment road, study construction craft and quality control request of 30# hard grade asphalt mixture , and through experiment road examination verify theories analysis and indoor experiment result.Through a great deal of experiment and theories analysis, obtain the following research result:(1) Using road use performance analysis, the 30# hard grade asphalt belongs to S class asphalt and contain lower amount of wax, and have smaller temperature sensitivity;The high temperature performance is very good and low temperature ductility index is worse. The construction temperature of 30# hard grade asphalt is higher, basically same as the polymer asphalt.(2) Put forward the reasonable gradation of 30# hard grade asphalt using at the mid or lower surface layer of asphalt pavement, research the parameter value scope of the Bailay method, establish the relationship of framework void of coarse-aggregate VCAAC with Bailay method parameter. The research of road use performance of 30# hard grade asphalt mixture show that it has very good anti-high temperature deformation ability, good water stability, and its low temperature property can satisfied the request of the mid or lower layer, its application has technique feasibility and economic reasonableness.(3) Analyze the compaction characteristic of 30# hard grade asphalt mix SAC20 , put forward the compaction method of 30# hard grade asphalt mix SAC25, provide a theories basis for the compacted density of 30# hard grade asphalt mixture.(4) First time making use of England Cooper multi-function asphalt material experiment machine measure the dynamic indirect tension stiffness of 30# hard grade asphalt mixture, and adopting Mathematical Statistics two variance analysis, research the affect of the main factor such as gradation, asphalt and aggregate ratio, test temperature and asphalt penetration.(5) Make parameter viscosity stiffness as the evaluation index of high temperature performance of asphalt mixture, establish the relationship of it with dynamic stability of rutting test. Compare stable creep test with dynamic creep test , obtain the deformation ratio of dynamic and stable creep of 30# hard grade asphalt mixture. Announced to public the clearly influence of framework density structure to the high and low temperature performance of 30# hard grade asphalt mixture.(6) Verify the reasonableness of Burgers model as the constitutional relationship of 30# hard grade asphalt mixtures to reflect its visco-elastic behavior, the parameter obtained can use to analyze and predict its visco-elastic property, which have importance meaning to rightness further deep understand the mechanics characteristic of 30# hard grade asphalt mixture .(7) Put forward the construction technique and craft request of 30# hard grade asphalt mixture , verify the reasonableness of indoor test and the feasibility of its application by investigate the using condition of test road after its open to traffic one year .The paper carried on system of experiment, analysis and research to the road using performance of 30# hard grade asphalt, the component ratio design ,compaction mechanism and method ,dynamic mechanics property and high and low-temperature performance etc. of 30# hard grade asphalt mixture , provided more integrity of theories basis for the 30# hard grade asphalt used for the mid or lower surface layer of asphalt pavement , also lay foundation for the hard grade asphalt research and expansion application in our country .