Discrete Element Simulation of the Internal Structures of Asphalt Mixtures with High Content of Tire Rubber

Document Type

Conference Proceeding

Publication Date



Department of Civil, Environmental, and Geospatial Engineering


Increasing rubber content in asphalt mixtures is recognized as a practical approach to consume fast-growing waste tires. The reacted rubber technology using the dry process was developed to address the rubber swelling and poor performance of rubber asphalt mixtures. Although the tire rubber has proved to increase the low-temperature performance, fatigue life, cracking resistance, and rutting resistance of asphalt mixtures, the impacts of high content tire rubber on the mixtures’ internal structures have not been revealed. This study is a preliminary research that utilized the laboratory and numerical simulation approach to investigate the strength, skeleton structures, and stress distribution of the tire rubber asphalt mixtures. The discrete element method (DEM) was employed to establish asphalt mixture models with a high content of tire rubber. New modeling procedures were developed to incorporate coarse aggregate shapes and rubber particles. Indirect tensile strength (ITS) values of specimens with rubber content up to 4.5% by mass were tested in laboratory and simulation. The results from DEM simulation had better consistency than the laboratory results. However, the test results showed that as the rubber content increased, the ITS of asphalt mixtures significantly decreased. Besides, the simulation indicates that the ITS decreased linearly as the percentage air void increased. The specimen ITS value decreased by half as the void ratio reached 15%. Furthermore, the internal structures and stress distribution of specimens with different rubber content were analyzed. The gap gradation proved to have a functional capacity of accommodating fine aggregates and rubber particles, all while forming a coarse aggregate skeleton.

Publication Title

Lecture Notes in Civil Engineering