Study Of High Modulus Asphalt Concrete Key Design Index And Design Method

Three kinds of asphalt mixture design system, which are widely used in the world, were researched in this paper which were Marshall design method and the American Superpave asphalt mixture design method which are assessed by the volume index and the French high modulus asphalt method which are mainly focus on the performance index of the asphalt mixture. This paper mainly compared and analyzed the differences between the French high modulus of asphalt mixture design method and Marshall asphalt mixture design method in the design concept, design method and key indicators and provided the technical foundation for us to study and digest the French high modulus of asphalt mixture design method. The main research contents and conclusions were as follows:According to the analyzing of low-grade asphalt mixture compacting temperature reference value recommended by France specification BS EN12697-35, we could get the low-grade asphalt mixture compacting temperature by using viscosity-temperature curve.The relationship of asphalt content and air voids determined by two different methods were analyzed. We could got from the analyzing that:for different aggregation type of low-grade asphalt mixture, when the abundance coefficient K equaled to3.4, the forecasted asphalt content agreed with the optimum asphalt content determined by Marshall method; when the asphalt mixture had same aggregation type and different asphalt grade (20#and70#), the forecasted asphalt content under abundance coefficient K equaled to3.4was0.2%higher than the optimum asphalt content determined by Marshall method. For the SGC samples with different aggregation type, different asphalt content and same compaction effect, the air voids measured by France height ratio method was about2%to3%higher than air voids measured by submerged weight in water, the regression curve equation was y=1.0399x+2.2751(R2=0.885). The significance indexes in significance testing of penetration, softening point, asphalt grade, asphalt content, abundance coefficient K, the France air voids VV, loading frequency f,∑(the parameter indicating the key size of France sieve), etc, which were considered in the analyzing of SPT test result under15℃testing temperature. The dynamic modulus were calculated by taking the logarithm, the dynamic modulus multi-element model and multi-element equation were established by using SPSS statistic software. The SPT test results were used to analyze the changing law under different aggregation type, asphalt content, and asphalt grade. We could get that:for low-grade asphalt mixture, the dynamic modulus multi-element model could not be used to forecast its modulus dynamic changing law under different aggregation type and, asphalt content, and asphalt grade, which mean that the traditional dynamic modulus multi-element model could not be used to forecast the changing law low-grade asphalt mixture under different condition.In this paper, the influence of asphalt grade, strain level, continuation aggregation and gap aggregation, aggregation type on the initial dynamic modulus and fatigue life. We could obtain from the result that:under the200με strain level and certain loading times, the stiffness modulus of20#base asphalt mixture was larger than70#base asphalt mixture, and the fatigue life of20#base asphalt mixture was4571times of fatigue life of70#base asphalt mixture was. The decreasing speed of fatigue life of samples with high strain level was bigger than samples with low strain level with the increasing of loading times. Under200με strain level, the stiffness modulus of continuation aggregation mixture was bigger than gap aggregation mixture, on the other side, the fatigue life of gap aggregation mixture was6.48E±12times of fatigue life of continuation aggregation mixture. For different design type, the order of different aggregation type was:for stiffness, AC-13continuation aggregation>EME2(0/14) continuation aggregation>EME2(0/14) gap aggregation; for fatigue life, EME2(0/14) gap aggregation> EME2(0/14) continuation aggregation> AC-13continuation aggregation.