Study On Road Performance Of Semi-flexible Pavement Based On Foam Warm Mix Recycled Asphalt Mixture Matrix

The hot mixing technology of asphalt mixture is the most commonly used construction technology of asphalt pavement in our country.The mixing temperature of hot mix asphalt mixture is usually between 150 and 180 ?.The formed pavement has good road performance,but the process of construction consumes a lot of energy,emits harmful gases and harms the health of workers.At the same time,the process of construction also aggravates the aging of asphalt,which reduces the service life of the pavement.In addition,hundreds of millions of tons of old asphalt mixture will be produced every year due to the maintenance and reconstruction of pavement in our country,and the efficient reuse of these old asphalt mixture resources has also become an urgent problem to be solved.The transportation construction industry is facing severe challenges in terms of environmental pollution and resource consumption.For this reason,this paper puts forward a semi-flexible pavement technology based on foam warm mix recycled asphalt mixture matrix,which accords with "green environmental protection production".The pavement material is a new type of composite pavement material-foam asphalt warm mix recycled semi-flexible pavement material,which is formed by adding appropriate amount of recycled material to the mineral aggregate,forming large gap warm mix recycled matrix by foam asphalt warm mix technology,and then pouring special cement mortar into the matrix and curing.The use of warm mixing technology can reduce energy consumption,harmful gas emissions and asphalt aging.Adding recycled materials to the mineral aggregate can achieve waste utilization and reduce the secondary aging of recycled materials.Foam asphalt warm mix recycling semi-flexible pavementtechnology is in line with the national concept of "green,low carbon,sustainable development".The main research work and achievements of this paper are as follows:1)In this paper,the foaming test design is carried out according to the foaming mechanism and characteristics of foamed asphalt,and the indoor foaming test is carried out by using WLB10 S indoor asphalt foaming tester.By improving the test method of expansion rate and half-life,the best foaming conditions of Foshan 70 asphalt are determined as follows:foaming temperature 155 ? and water consumption 1.5%.2)The test results of raw materials and recycled materials meet the requirements of the specification,and the contents of five kinds of recycled materials are 0%,15%,30%,45%and 60% respectively.Combined with the characteristics of large voids in the matrix asphalt mixture,the gradation design is carried out by using the main aggregate void volume filling method.Then through leakage analysis and dispersion tests,it is found that the optimum asphalt content of the matrix with different recycled material content is 3.5%,3.56%,3.68%,3.81% and 3.97% respectively.The test results show that the performance of the warm mix recycled matrix asphalt mixture formed according to the design mix is in line with the technical index.3)The dry powder of special mortar is prepared into cement mortar according to different water-cement ratio and sand content,and the performance of cement mortar is evaluated by fluidity,flexural strength,compressive strength and dry shrinkage,and finally determined that the water-cement ratio is 0.22.The cement mortar with 20% sand content has the best grouting effect and mechanical properties.4)The Marshall and rut board matrix specimens are prepared according to the warm mix process,and the warm mix recycled semi-flexible pavement materials are formed according to the improved semi-flexible material preparation technology.After a certain age maintenance,relevant laboratory tests were carried out to evaluate its road performance such as high and low temperature performance,water stability and fatigue performance.The test results show that the road performance of warm mix recycled semi-flexible material is obviously better than that of ordinary hot mix asphalt mixture,and it has excellent anti-rutting and water damage resistance as well as certain anti-fatigue performance.5)As the semi-flexible material has the characteristics of asphalt mixture and cement concrete at the same time,its ability of anti-cracking is slightly poor.Aiming at the bottleneck of anti-cracking performance of semi-flexible pavement,this study analyzed the influence of interface weakening of hot-mixed recycled semi-flexible material on the internal stressdistribution of the material through digital image processing technology and ABAQUS finite element software.The study shows that the interface structure of the semi-flexible material has a certain ability to resist deformation,and it can absorb part of the stress under load to reduce the internal strain of the material.improving the strength of the interface structure can effectively enhance the overall cracking resistance of semi-flexible materials.