Structural Behavior of Asphalt Pavements by Lijun Sun
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Structural Behavior of Asphalt Pavements by Lijun Sun

PREFACE to Structural Behavior of Asphalt Pavements:

When current knowledge could not explain the questions we are facing, we prefer following our inner feeling to insight and grasp the beautiful essence in pavement world, and trying to shape them into science level, rather than defend tenaciously those fragmented experience knowledge although those were classical.

Since 1991, my research interests have transferred partially from the pavement management area to the asphalt pavement area. In that time, the research on asphalt pavement has had a long history and made brilliant achievements in the world.

But in China, the research history on asphalt pavement was not very long, and the engineering experiences were not so rich. This is why I decided to select the asphalt pavement as my long-term research area. With the freeway forming a whole network in China, the traffic volume and axle load magnitude has increased sharply.

The national average percentage of trucks on the freeway is 40%, and the heavy weight of these vehicles causes a very serious premature distress of the pavement.

Over more than two decades, many new pavement techniques, such as modified asphalt, SMA, Superpave, long-life pavement, and high-modulus asphalt, were introduced into China so promptly that the development of the pavement techniques seemed to be booming.

Additionally, a large amount of research on asphalt pavement structure and material were conducted throughout the world in order to face up to the challenges from the heavy load of vehicles.

Some researchers made great efforts to integrate the fragmentation pavement research results into a comprehensive theory for pavement analysis and design, but the effectiveness of this practice does not look as significant as expected.

These research results are considered to be the simple extrapolation of conventional theories and methods for light-duty pavement, which is well suited for the analysis and design of conventional asphalt mixture, but not for emerging materials.

These results cannot reflect the performance of pavement, nor can they give a clear guide to pavement component design; therefore they are considered only little help in solving the problems of very heavy-duty pavement structures.

We face a number of questions and challenges, including: how to effectively solve pavement problems due to extremely heavy loads; how to consider emerging materials and techniques in pavement design; and how to integrate the new techniques, new materials, and new concept together for success.

With this in mind, we started our pavement research. In fact, the aforementioned challenges became the drive for us to adhere to asphalt pavement for more than two decades. The pavement world is so complicated that we cannot see the direction ahead.

But in the vast mist there is always a flickering dim light leading us to pursue, not see the truth, hard to shake off. Over the years, the encourages from some predecessors excited our often languorous spirit, the doubt and controversy from some colleagues helped us improve our researches.

By the end of 2001, we had finished the first stage in our research of pavement behavior, and by 2005, we had formed a clear framework on the asphalt pavement behavior. Since then, we have supplemented the research on the pavement deformation, which now forms today’s pavement behavior dynamics.

The publication of this Structural Behavior of Asphalt Pavements book means that the pavement research we began in 1991 is now coming to an end. The “new students” who participated in this early round of research in my group are now the “senior experts” in the Chinese highway field.

With over two decades of research, we came to realize the behavioral characteristics of the asphalt pavement structure and the limits of mechanistic analysis.

The asphalt pavement is so complex that the modern mechanistic theory can only help qualitatively analyze the known phenomenon, but it cannot accurately reflect the complicated performance of asphalt pavement structure and materials.

Therefore, it is difficult to discover unknown laws for asphalt pavement, as any guide available is very limited in practice. This may be the basic reason that empirical analysis and design still play dominant roles in pavement practice.

In order to understand the accurate behavior characteristics of asphalt pavement, it is necessary to develop a new roadmap, based on which the integration of theoretical analysis, test result, and engineering experience

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