Behaviors of Intermediate Layer "BASE COURSE" used on the Construction of Highway

Pavements are a layered system, each layer is distinguished by different materials as required by traffic and subgrade conditions. A base course is an intermediate layer constructed of high quality stone aggregates: quality based on physical properties such as gradation, hardness, and texture. This thesis presents the results of a comprehensive experimental testing program that was conducted to examine the behavior of unbound granular base materials under cyclic loading and to evaluate the effect of the stress level and moisture content on strain behavior. Three base materials, namely granite, limestone and sandstone, were selected. Three different types of RLT tests were used including: resilient modulus, single-stage, and multi-stage RLT test. The single-stage and multi-stage RLT tests results were analyzed within the framework of the shakedown theory. The results of this study showed that for resilient modulus the materials preformed the following, with the materials listed highest to lowest: limestone, granite and sandstone; while for permanent deformation, the materials were listed highest to lowest: sandstone, limestone and granite. In addition, the results demonstrated that the change in slope (m) of shakedown limits with the degree of saturation was more pronounced at lower stress levels (elastic limit) than that at higher stress levels (plastic limit). Finally, the results showed a significant effect of degree of saturation on the intercept of the shakedown limits at both low and high stress levels. The change in intercept was greater forlimestone than sandstonefor changesindegree of saturation.