Abstract
Hot Mix Asphalt (HMA) pavement is most used in road construction in Iraq due to its economic benefits and ease of maintenance. Several factors are affecting the performance of HMA in the field. One of the major factors is aggregate gradation. The Universal Specification for Roads and Bridges in Iraq (SCRB) specifies limits for the different types of asphalt layers and allows tolerance for the designed aggregate gradation. In the current asphalt industries, it quite difficult for contractors to achieve the required job mix due to difficulties in sieves control. This study concentrates on the effect of aggregate gradation deviations on the required specification performance. A mid gradation of the binder asphalt mixture was selected as a reference mix and more than 20 deviated mixtures were then prepared. Typical Marshall routine trials were performed on the prepared admixtures to evaluate the mixture properties. Bailey packing theory for mixture evaluation (Coarse Aggregate Ratio CA, Coarse Portion of Fine Aggregate FAc ratio) was also used to understand the impact of these deviations on the particle arrangement and mixture performance. Results showed that minor aggregate deviations do not greatly affect the mixture performance, however, a large deviation in coarse aggregate results in a drop in Marshall properties. Results showed that the Bailey method for performance evaluation is a good tool to understand the mixture performance. This paper aims to study the influence of aggregate gradation deviations on the mixture performance.
Published Version
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