ABSTRACT Research to modified asphalt or asphalt mixture is always very popular in highway engineering．SBS modified asphalt has been occupying the leading position for a long time，nevertheless，it is necessary for researchers to enrich and develop the measure or approach of asphalt modification．Natural asphalt has its unique predominance because it was formed naturally；hence，it is significant for engineer to adequately use this kind of resource to modify asphalt． Button rock asphalt is a kind of natural asphalt having a shape of granule and power which was produced in Indonesian，where it was used broadly，and was introduced into China just in recent years，therefore，there isn’t enough information of its engineering application．This essay，commissioned by Shandong provincial transport department 2003 science & technology conquest program “Button rock asphalt modified asphalt mixture test research”，has done a series of research to the application of Button rock asphalt in pavement engineering and made some suggestions about asphalt mixture design theory. The electrical mirror analysis results to Button rock miner and its asphalt demonstrate that Button rock asphalt contains many elements such as C、H、O、S、Si、Mn、AI、Ca and Fe ere．Comparing with common petroleum asphalt，researcher finds that pure Button rock asphalt contains more asphalt alkenes however less pectin if divided into four kinds of components，this makes it showing some characteristics such as high consistency and softening point whereas low extensibility and good adhesion character and temperature stability etc．High temperature performance of asphalt modified by pure Button rock asphalt was greatly improved whereas its low temperature performance was worsened almost in the same extent．Button rock asphalt could improve high temperature performance，even if directly mixed into common asphalt mixture，the dynamic stability of Button rock asphalt mixture could surpass 3500 time per millimetre when 4.5 percent of total miner content comes from Button rock. Researcher creates Burgers model based upon high temperature bend creep test and finds that four parameters of model add geminately，the instantaneous elastic module of Maxwell model is 5.7 times of common asphalt mixture and coefficient of viscosity high to 10 times，the elastic constant of Kelvin model is 2.6 times and coefficient of viscosity is 4.2 times．These data opens up a phenomenon that Button rock modified asphalt has good high temperature performance．Single axis compression test demonstrates that the renounced module of asphalt mixture modified by Button rock asphalt enhances nearly geminately．Stress relaxation equation shows that the stress relaxation performance of Button rock asphalt mixture is better than common asphalt mixture．As for content of Button rock asphalt，the optimum quality ratio is 1：0.8～1：0.9 between Button rock asphalt and common asphalt after considered water stability． The paper recommends that Button rock asphalt should be used in the area where the temperature is high． In the theory of asphalt mixture design，there are some problems in connection with the understanding on the asphalt mixture volume indexes，including the air voids，the voids in the mineral aggregate，the values of percent voids in mineral aggregate filled with asphalt and SO on．In this paper，the meanings of them and the relationship among them are discussed comprehensively and meticulously，some vague understandings are clarified．Then，some interesting facts are discovered and new formula used to calculate the effective asphalt content directly is raised，according to grey system theory．the regularity between curve position and the air voids in the gradation curve of asphalt mixes is elicited，which is that the similarity of the gradation curve of asphalt mixes and theoretical maximum density curve determines the air voids．the more the similarity the smaller the air voids．So the usual method that attempt to change the air void of the asphalt mixture by estimating the curve position and adjusting it is not dependable．On the support that the aggregate gradation has been determined，the formula used to calculate a narrow range of optimum asphalt content with the standard of the volumetric index is derived from the formulas used to calculate the air voids，the voids in the mineral aggregate and the values of percent voids in mineral aggregate filled with asphalt for the first time，the method that can predict the optimum asphalt content is raised，which is suitable for various kinds of asphalt mixture design methods．Based on the volumetric design method of gap graded HMA，considering its weaknesses，using the formula derived above and knowing the voids in the mineral aggregate，a group of equations used for design method of dense built-in gradation al e established preliminarily．Because the tests used to judge interlocking conditions of the aggregates during designing the SMA mixture have too much numerous，a short-cut method that needn’t many tests but calculation is developed，which Can easily judge interlocking conditions of the aggregates． At last，the technology and quality control of the BUTON rock asphalt modified asphalt mixture ale expounded and some related problems that will be studied further are discussed briefly． Key Words：BUTON rock asphalt，Modified asphalt mixture，Capability，Range of optimum asphalt content，Aggregate grading design，Short-cut method for judging interlocking conditions |
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