Experimental Study On Recycling Methods Of Asphalt Pavements

The highway engineering of China is coming into a new era characterized by equal priority of construction and maintenance. Problems of striving for budget and resources have arisen in succession. It is anticipated that the challenges of technology, materials, resources and environment in this period will be much more complex than those in construction phase. Plenty of pavements built by modified SMA which had excellent service performance are facing the requirement of maintenance in succession. Piling and downgrading of the aged materials will give great pressure on environment and cause huge problem on resource. The recycling technology of asphalt pavement is attracting attention because of its technical superiority and the consistency with the concept of circular economics of resource-saving. The study on recycling of modified SMA pavement is almost blank in ChinaA combination of theoretical analysis, indoor experiment, in-situ experiment and numerical simulation has been systematically conducted in this study. A review of new developments and improvements is summed up while problems in practice and flaws in theory are both stated. Mechanism of aging and recycling of ordinary asphalt and modified asphalt are analyzed based on their colloidal structures and molecular structures. By experiments of short term and long term aging, the changes of asphalt property indicators are verified. The aging and recycling mechanism has been studied from a microscopic perspective by Infrared Radiation and Gel Permeation Chromatography. A rejuvenator for ordinary asphalt and a composite rejuvenator for modified asphalt have been developed based on the fundamental principles of rejuvenator. Experimental data have verified the validation of rejuvenator. The relationship between content of rejuvenator and recycling asphalt performance has been built. Centrifuge particle size and centrifuge velocity are analyzed by settlement theory and centrifuge theory. The extraction and recovery methods are improved after comparison of them. An "aging in indicators" caused by mineral powder and a "secondary aging" caused by solvent have been presented.The recycling objects include base asphalt, modified asphalt and modified SMA. Two recycling methods are involved in this study, with rejuvenator and fresh asphalt binder respectively. A progressive recycling proposal has been discussed to extend the life-cycle of recycling asphalt materials. The proposal verifies the concept of recycling determination under different conditions as well. The idea of secondary modification is put forward to benefit the continuity of recycling technology for modified asphalt.In extraction and recovery process of asphalt in SMA, an improved method has been developed and aged fibers have been collected. It is demonstrated that the fibers in SMA would age during pavement serving time as well, and the stage of aging are estimated. The reinforcing mechanism of fibers is discussed. The feasibility of SMA recycling and fiber adjunction has been proved. Moreover, a throughout experimental study on the performances of recycled asphalt, recycled modified asphalt and recycled SMA has been conducted.Based on the analysis of the principal property indicators of recycled asphalt, an indicator of recycling capability is introduced. A method of determination of recycling opportunity can be established with a certain guarantee on the base of penetration of aging asphalt. These two indicators are valuable in evaluating the effect of recycling and determining the recycling design...