Development of Balanced Mix Design Quality Control Specifications Based on the Acceptance Limits of HMA Performance Tests
With the augmented use of recycled materials, recycling agents, modified binders, and warm mix asphalt additives, several highway agencies including the Texas Department of Transportation (TxDOT), have considered methods to improve the durability and long-term performance of asphalt concrete (AC) mixes. The need for performance tests that could consistently evaluate the rutting and cracking potentials of AC mixes became crucial as the popularity of the Balanced Mix Design (BMD) concept has increased over the years. A concern now is related to the practicality of these tests for routine use in the process of quality control and quality assurance during the field production phase, especially the tests performed to assess the cracking resistance, which is now the primary mode of distress for AC mixes. This thesis presents an experimental evaluation that was elaborated for the development of BMD quality control guidelines based on acceptance limits of hot mix asphalt (HMA) performance tests for the assessment of cracking potential during the field production phase in Texas. Four different approaches were developed to correlate the performance test results. The correlation was based on the average values of the crack progression rate (CPR) from the Overlay Tester (OT) test, and the average values of the crack tolerance index (CT Index) and indirect tensile strength (IDT) from the indirect tensile asphalt cracking test (IDEAL-CT). These approaches will be demonstrated using six field projects constructed throughout the state of Texas. These projects cover twenty sections with various AC mixes including a thin overlay mix (TOM), four densegraded (DG) and fifteen Superpave (SP) mixes with four different aggregate types, and four neat asphalt binders with specified PG 64-22, PG 70-22, PG 70-28 and PG 76-22. These mixes were designed based on the BMD concept following a volumetric design with a performance verification approach. The mechanical properties of the AC mixes were evaluated by performing tests on different asphalt contents including the optimum asphalt content (OAC), OAC-0.5%, and OAC-1.0%. The OT test and the IDEAL-CT test were used to assess the cracking resistance of the AC mixes, and the Hamburg wheel tracking test (HWT) was used to assess the rutting resistance of the AC mixes. These results were presented on the performance space diagram to check whether the mix is balanced at OAC. Given the promising results, the proposed approaches could be potentially implemented to enhance practicality during the field production phase.
Abrantes, Lucas Tameirao, "Development of Balanced Mix Design Quality Control Specifications Based on the Acceptance Limits of HMA Performance Tests" (2022). ETD Collection for University of Texas, El Paso. AAI29324355.