Masato Murayama

Development of high stability hot mix asphalt concrete with hybrid binder

Abstract: Cost reduction of public works projects has been desired due to severe financial circumstances. Therefore, asphalt pavement has been requested to extend its life. Semi-flexible pavement or epoxy asphalt pavement, which has high rutting resistance and oil resistance, may be applied to the place where these performances ae demanded. However, special technique is required in manufacturing and construction. In addition, these materials have also raised a problem that they cannot be recycled. Meanwhile, conventional asphalt pavement has several drawbacks. It is vulnerable to rutting caused by traffic load and damage caused by petroleum oils such as gasoline or motor oil. The materials used in asphalt mixtures were studied for improving the durability of asphalt mixture. A high stability asphalt concrete was developed which has equal or superior performance to semi-flexible pavement and epoxy asphalt pavement. In this paper, the process of selecting the substance and the characteristics evaluation of the developed mixtures ae described. Furthermore, an inspection result as well as follow-up survey of the performance of the developed mixtures obtained from trial and actual construction is shown.

A Study of Longitudinal Crack Which Occurs to the Surface of Asphalt Pavement by Wheel Tracking Test

It is known that asphalt pavement is subject to longitudinal cracking that begin at the surface and propagate downward. The main mechanism involved is considered to be bending-induced tensile strain away from the tire or shear-induced near-surface tensile strain at the tire edge. It is difficult to specify the location where such cracks occur because vehicles do not follow precisely the same path. Some cracks might form beneath the tire of a vehicle. However, no reliable method has yet been established. The purpose of the present study was to identify the mechanism involved in longitudinal cracking in asphalt mixtures using an improved wheel tracking test. By varying the temperature and loading conditions, it was determined that cracking occurred beneath the tire. The cracks had similar shapes to the longitudinal cracks that occur in road surfaces. The bottom surface of the asphalt showed no evidence of cracking. To determine the reason for this, stress relaxation in an asphalt mixture was investigated using compression tests. As the results, the stress-relaxation performance of an asphalt mixture becomes higher as temperature increases. Moreover the compressive stress was reduced immediately to about half of its maximum value. This suggests that if the compressive stress in the surface layer is released, the residual strain in the binder course layer would act as a tensile strain, which gives rise to the formation of cracks.