Applied Research Of Modified Asphalt(SMA) In Frozen Areas

Along with the development of national economy, the demand of transportation enlarges continuously, asphalt concrete pavement is facing critical trials in every aspect. Some new road pavement structures,new materials and new techniques have already been applied successfully in our country. Study and tally up these new asphalt pavement structure are of very important realistic meanings, i.e. speed up the construction step of expressway asphalt concrete pavement, raise the engineering quantity, perfect the functions of asphalt concrete pavement, prolong its service life and economize the investment, etc. The asphalt mastic macadam pavement (hereinafter referred as SMA) is a totally new type of pavement structure concerned by the whole world. The asphalt mixture is the kind of coarse aggregate skeleton filled with the asphalt mastic mixture composed by bitumen, fiber stabilizer, mineral powder and less fine aggregates. It is a noticeable new asphalt mixture in the world, and it is well known by its good performance of rut-resistance, skid-resistance, temperature stabilization, durability, surface characteristics and income on investment. SMA is a system made up by three phases: mineral granular, asphalt slurry and air, in which the mineral skeleton is composed by coarse and fine aggregates, it is a non-continuous phase, but the asphalt slurry is a dispersing agent. In accordance with the internal structure features, there are two types of asphalt mixtures commonly used: one is dense graded asphalt mixture, it is designed on the basis of continuous grading theory. Because of more contents of fine aggregates in the mixture, the mineral particles are to be bond to the asphalt, and the coarse aggregates are squeezed apart by the fine aggregates. Therefore, the coarse aggregates suspend in the mixture, it is of the suspending dense structure with characteristics of high density but less stability. The other type of mixture is the open graded asphalt mixture with less fine aggregates, the coarse aggregates are not noly bond densely but also with high rates of voids. Inner friction of the asphalt mixture plays a very important role, cohesion can only stabilize the aggregates, it belongs to the skeleton void structure. This type of mixture is affected little by the changes of bitumen and with high stability. At present, the research of SMA and modified asphalt tenique becomes very popular. With thorough study, modified asphalt (SMA) has already been concerned extensively. Currently, modified asphalt (SMA) technique has been greatly applied in the engineering. There is a need to carry on systematic research of asphalt SMA technique, for tallying up the domestic and international advanced experiences, finding out the the right SMA technique adapted to cold region, construction of SMA pavement with good quantity and good performance, attaining the targets of improving pavement quality, prolonging the service life and raising comfort and safety etc. On the basis of indoor experiments, the thesis has done enormous research on application of SMA, it is to solve the problems of rut-resistance under high temperature and crack-resistance under low temperature, improving the water stability, aging-resistance and comfortability etc. The detailed research contents include: 1. With enormous information and data, we studied the development condition of SMA in foreign countries, and according to the actual circumstances of the state, we did research on modified asphalt (SMA) application technique for cold region. 2. Taking Changyu Expressway as the study background, the SMA mineral aggregates gradation is defined on the basis of great deal investigation of SMA mineral aggregates gradation. 3. Trials are excuted for the designed SMA gradation, even design optimatic method is adopted for research of granular gradation. Quatrature design method is adopted for study of mastic performance. Experiments are carried out for the stability under high temperature, water damage-resistance and alternation of freezing and thawing. Comparisons are carried out between the trial results ofmodified asphalt (SMA) mixture and the common asphalt mixture. 4. The modified asphalt (SMA) can prolong 50% service life of asphalt pavement and raise the pavement performance. Through investigation on modified asphalt (SMA) technique in cold region, and on basis of enormous trials, the results prove that: Modified asphalt (SMA) can bear large traffic volume with good performance, after the project is open to traffic, it would help to lower maintenance fee, improve the skid-resistance, reduce accident rate, improve evenness of pavement, increase driving comfortability, reduce noise and good for environmental protection, it would produce great economic and social benefits.