Date of Award


Degree Name

Master of Science


Civil Engineering


Soheil Nazarian

Second Advisor

Imad Abdallah


With the rapid paradigm shift of pavement design methodology from an empirical-based approach toward a more mechanistic-based approach, the existing mix design processes also need a radical shift from the conventional volumetric-based methods to performance-based methods. The use of a volumetric-based design methodology has become more challenging due to the increasing use of recycled materials, modified binders, warm mix asphalt additives, compaction aids, and rejuvenators. A shift toward the more fundamentally sound â??balanced mix designâ?? (BMD) concept is envisaged to produce asphalt concrete mixtures with acceptable performance in terms of durability and stability. Aggregate gradation plays a crucial role in achieving this balance between durability and stability. Previous studies have been carried out delineating various gradation parameters but very few studies deal with the implementation of these parameters and their relationship to asphalt concrete (AC) performance.

Improving the durability and long-term performance of AC has become a major concern after the use of Superpave specification, especially with the increase in the use of recycled materials, warm mix asphalt additives, and modified binders. The major objective of this study is to propose a gradation design tool as part of a transition towards the balanced mix design principles. The scope of the study consists of reviewing the existing gradation parameters and their relative impact on mixture volumetric and mechanical properties of Superpave mixes. This information was translated into a web-based â??Gradation Design Toolâ?? which can be used to optimize the gradation based on different gradation parameters. This tool was then used on six test sections across Texas to study the volumetric and mechanical behavior of the proposed mixes. Each test section had a control gradation mix and at least two other mixes to study their relative difference in properties.

A â??volumetric design with performance verificationâ?? method is used to ensure satisfactory mechanical performance during the balanced mix design process. TxDOT-approved performance tests are used to evaluate and balance the rutting and cracking potential of the mixes. A performance space diagram formulated with the crack progression rate from the Overlay tester test and normalized rutting resistance index from the Hamburg wheel tracking test was utilized to characterize the mixturesâ?? performance. To evaluate the potential of using the performance tests during the QC/QA process, the cracking tolerance index from the indirect tensile asphalt cracking test (IDEAL-CT) was used as a surrogate parameter. The optimization of the aggregate gradation is a promising approach to formulate a mixture with balanced stability and durability.




Received from ProQuest

File Size

80 p.

File Format


Rights Holder

Prathmesh Deepak Jichkar