| With the rapid development of China’s economic,the increase of passenger and freight vehicles on high-grade highways,the phenomena of heavy load and overload increase sharply,the rutting problems of asphalt pavement is sharpening quickly.Stone mastic asphalt mixtures(SMA)have been widely used in modern high-grade road construction due to its excellent characteristics.The structural characteristics of“three more and one less”are that there are many coarse aggregates,more ore powder,more asphalt,and less aggregates,which makes the asphalt mixture have better road performance.The incorporation of fibers as stabilizers into the SMA mixture has the effect of preventing asphalt leakage.The results show that the effects of different kinds of fiber stabilizers on the properties of mixtures are different.Therefore,the basalt fiber(BF)and cellulose fiber(CF)are mixed into the SMA mixture,and the properties of the two materials are used to comprehensively improve the performance of the mixtureFirstly,the physical and chemical properties and micro-morphology of basalt fiber and cellulose fiber were measured.The results show that the mechanical properties of basalt fibers are better than that of cellulose fiber.The dispersion of basalt fibers is better than that of cellulose fibers,which are long straight shape;while cellulose fiber has strong adsorption capacity,flat and curved,rough and staggeredSecondly,basalt fiber and cellulose fiber were added into asphalt according to the blending ratio of 3:0,2:1,1.5:1.5,1:2 and 0:3.The effects of fiber blending on the indexes of high and low temperature and rheological properties of SBS modified asphalt and absorbing asphalt capacity were analyzed by softening point,ductility,dynamic shear rheological test and net basket leak test.The results show that the addition of fibers can effectively improve the softening point and rutting factor of fiber asphalt,and the ductility test is not suitable for evaluating the low temperature performance of fiber asphalt,cellulose fiber has the highest oil absorption rate Scanning electron microscopy(SEM)was used to observe the distribution and micro-morphology of the two kinds of fibers in modified asphalt.The interface theory of composite materials was used to analyze the mechanism of fiber asphalt.It was confirmed that the basalt fiber and the cellulose fiber were mixed to enhance the interfacial bonding effect with the asphalt.The two kinds of fibers and the asphalt overlap each other to form a structural asphalt network,which could increase the adhesion and crack resistanceAgain,select the appropriate SMA-13 grade.The Marshall specimens of SMA-13 mixture were formed according to the above-mentioned compound blending ratio of fibers.The variation of volume parameters of SMA-13 mixture with the ratio of asphalt to aggregate and fiber to aggregate was studied.The results show that the relative density of gross volume and asphalt saturation of the specimens increase with the increase of the designed asphalt-aggregate ratio,while the voidage and mineral material voidage decrease with the increase of the designed asphalt-aggregate ratio.The optimum asphalt-aggregate ratio of asphalt mixtures with different fiber mixing ratios is determined.It is found that with the increase of cellulose fiber content and the decrease of basalt fiber,the optimum oil-aggregate ratio increases,the gross volume density decreases,and the mineral interstitial ratio increases.The mineral interstitial ratio VMA of single basalt fiber asphalt mixtures is about 1%smaller than that of single cellulose fiber asphalt mixtures.Finally,the high temperature performance,low temperature performance,water stability and fatigue performance of SMA-13 mixture with different fiber mixing ratio were studied.When the dosage is constant,the increase of cellulose fiber content leads to the decrease of high temperature and fatigue performance of the mixture,and the low temperature performance is improved.When the fiber is BF:CF=1.5:1.5,the water stability evaluation index is better.However,the single-blended BF mixture has high stability before and after immersion in water,and has good durability.Efficiency coefficient method is used to evaluate the road performance comprehensively,and the mechanism of fiber reinforced asphalt mixture performance is analyzed from the micro point of view.The results show that basalt fibers and cellulose fibers play their respective structural advantages and improve the road performance of the mixture synergistically.This study provides some suggestions for the design and application of basalt and cellulose fibers in SMA mixture,and has certain theoretical and popularization value. |
