Research On Distress Cause And Prevention Of Highway Asphalt Pavement In Zhejiang Province

With overall national strength increasing, highway construction has taken huge achievement. However, highway construct being later, increasing of traffic and shaft-carrying, the advance of construct requires, the impersonal factors such as country situation, climate, geomorphology, traffic volume increasing with more heavy traffic, traffic vehicle channeling, the asphalt mixture surfaces of highway are facing severe test tests. Mature failure have taken place here and there, some have surface failures such as cracks, rutting, flushing oil, pavement pit, chap, caves and vehicle-jumping even in one or two years after opening traffic. These have badly affected normal use and vehicle safety of highway, moreover taken more maintaining costs.Through investigating typical surface failures of asphalt pavement in Zhejiang province, such as scurrying by water breakage, looses, tracks, sinking, it is shown that the structural design including base, void ratio in asphalt mixtures, thickness, drainage design, aggregate gradation, climate, raw material, construction and maintaining can cause surface failures.The semi-rigid bases under the asphalt mixture surfaces have better pressure and bearing, it also often causes basal reflected cracks. So more attention should be paid to highway design. Some measurements such as pre-cutting seam, the cling between asphalt mixtures surfaces and semi-rigid bases can improve the above problem.According to the investigated results and the cost of highway construct, the thickness of asphalt surfaces is advised between 16cm and 18cm, and the nominal maximum size of aggregate of surface layer should be 13.2mm, such as AK-13 or AC-13 S. If the nominal maximum size of aggregate of upper asphalt mixture is 16mm, the minimum thickness should be not less than 45mm.The void ratio in asphalt mixtures is related to the performances such as seeping, durality , high temperature stability and strength. So, the gradation design of asphalt mixture based on the air voids is very important. On the premise of void ratio meeting aquirement, we can consider the index of high temperature stability, economy and select the appropriate gradation of asphalt mixture.The AC-13 S gradation asphalt mixture based on the air void has some characteristics such as less nominal maximum size of aggregate and less fine aggregate, more medial coarse aggregate and appropriate mineral powder. The test result shows that it has better dynamic stability, appropriate percent air voids in asphalt mixture and lower cost. Through the maintaining of Hangzhou-Jinhua-Quzhou Highway (HJQ Highway) of Zhejiang, it is found the AC-13 S gradation asphalt mixture has good performance.Because water is one of the important factors of the highway surface failures, the drainage design is emphasized. The drainage designs of base, surface road should be systematized to increase the performance of resist-moisture damage of highway.It is also advised to strengthen the management and maintaining of highway and supervise on over-freight vehicles.