Research On Hot In-Place Recycling Technology Of Asphalt Pavement

With the rapid development of highway construction in China, the high-class highway has entered the period of large-scale maintenance. The research on recycling technology of asphalt pavement is an important task for the highway construction. Compared with ordinary asphalt, the modified asphalt has been widely used for its better performance. As the modified asphalt has been used on a large scale only for a short time and the current recycling technology focuses on substrate asphalt, with some facters such as unpretictable aging properties and comparatively complicated recycling design involved, the applied research on the recycling of modified asphalt is still in the infant stage in the world. On the practice basis of the construction of hot in-place recycling section of left-panel large-scale expansion project of the east highway of Hainan from Fucheng to Qionghai, this paper will conduct the research on hot in-place recycling technology of ordinary asphalt pavement and PE modified asphalt pavement, which will lay a good foundation for its application and promotion, and also provide a valuable reference for the research on sets of recycling technology of asphalt pavement.Hot in-place recycling technology has certain conditions of use, therefore, first of all,a detailed investigation and testing which is done about historical information on the old road, the original technical condition of the road, traffic and other aspects before the application, old asphalt pavement performance is evaluated. Especially bearing capacity of pavement structure provided basis for selection of hot in-place recycling technology program and the division of regeneration section. Through the test of the old road material properties, the materials used in Existing pavement structure and current situation are determined and evaluated. Diseases and causes of the old road are analyzed on the basis of it.Whether reuse of old asphalt mixture is related to evaluation of aging. First of all, test methods for recycling and extraction of old asphalt which is improved is studied, Fourier transform infrared spectroscopy, four components, three indicators, Brookfield viscosity and DSR, and other tests are carried out for the old ordinary asphalt which is extracted and modified asphalt, performance indicators of the old asphalt are determined, aging is evaluate, aging mechanism is analyzed. Aggregate performance, grading distribution and variability of the old aggregate is studied. Technical requirements and types of recycling agent are proposed. Recycling agent including components which is the absence of the old asphalt is selected. The old modified asphalt and ordinary asphalt blending with different contents of different types of recycling agent is recycled asphalt. Four components, three indicators, Brookfield viscosity and DSR, and other tests are carried out. Variation of The indicators is studied, the regeneration of recycling agent is comparative analyzed, Thus recycling agent and their dosage range based on engineering requirements is recommended, and performance test of recycled asphalt is done with the method of SHRP. The main flow of recycled asphalt design is summarized on the basis of it, the relational model of recycling control targets and regenerated content to determine the design content of recycling agent.The performance of recycled asphalt mixture is not only the key of the success of regeneration design, but also the main determinant of using life and quality of recycled asphalt pavement. Therefore, first of all, design method of hot in-place recycling asphalt mixture is selected, different designs of recycled mixture are proposed. Then test is carried out for the conventional mechanical properties, temperature stability, water stability, fatigue performance of recycled asphalt mixture. Change rule of the high low temperature stability and water stability of recycled asphalt mixture blended with the old and the new material dosage proportion. Remixing regeneration and repaving regeneration all can obviously improve aging properties of the old asphalt mixture, make its high/low temperature performance, water stability improved. Selecting appropriate regenerative agent and dosage, blending ratio of new old material can make recycled asphalt mixture performance reaching requirements specification is proved. Meanwhile, proposed control range and methods of the recycling asphalt mixture performance index is proposed.Through indirect tensile fatigue tests, this article studies the fatigue properties of different recycled asphalt mixtures and the old materials. The results shows that compared with the old materials, the fatigue characteristic parameter'k'of recycled mixtures increases significantly, which indicates that the fatigue life resistance has been improved greatly. The range of variation of the fatigue characteristic parameter'n'is not large, which implies that the sensitivity to stress of the fatigue life of the aging asphalt and recycled asphalt mixtures decreases. Under the same stress, the fatigue life of the recycled asphalt is apparently longer than that of the old materials. With APA round-return wheel load simulation structural tests, the essay further compares and analyzes the fatigue life of the recycled asphalt pavements, the conventional asphalt pavements and the old asphalt pavements in different recycling projects. The results show that the recycled asphalt pavements have longer fatigue life, which is consistent to the results of the indirect tensile fatigue tests.Through on-site tests, such as infrared thermal imager, small-size weather station, the article studies the effects of the weather conditions during construction and the status of the old asphalt pavement materials to on-site regenerative heating. By indoor and outdoor tests, it comparatively studies the effects of renewable technological parameters, such as regeneration temperature, regeneration asphalt mixing time, to regeneration results. Thus, it puts forward the corresponding on-site heating process and regeneration requirements.Based on these studies, combined with the on-site tracking and monitoring, the study further evaluates the adaptability of on-site heat regeneration technology.