Redesign of Brisbane City Council's Type 3 Asphalt and Development of Mix Specific Flexural Master Curves

Kidd, Andrew (2017) Redesign of Brisbane City Council's Type 3 Asphalt and Development of Mix Specific Flexural Master Curves. [USQ Project]


Brisbane City Council is the largest local council in Australia, and is responsible for the operation and maintenance of a sealed road network spanning over 5,700km. As such, BCC are continually seeking to improve their network in regards to pavement materials and testing innovations in order to provide value for money for ratepayers. This project examined BCCs surfacing dense grade asphalt mix design for moderate to heavily trafficked sections of the network, an 18mm aggregate size mix known as Type 3. Concerns were raised from internal and independent reviews that this design was prone to in situ segregation and permeability, and may not contain sufficient bitumen contents to ensure adequate durability. Additionally, it was observed that modulus values used in pavement design were based on outdated resilient modulus tests, and may no longer be relevant.

This project aimed to research, prepare and assess a number of best practice alternative designs with varied aggregate gradation shapes and increased bitumen contents in order to reduce mix segregation potential and improve workability, permeability, rut resistance and durability. These alternative design gradations were assessed using quantitative models based on Fuller maximum density equations to examine potential relationships. BCCs specification for Type 3 asphalt was also reviewed and compared against other local and international surfacing specifications to identify areas for improvement. Additionally, in order to provide modernised pavement modulus values at a range of practical pavement temperatures and vehicle speeds for BCCs network, it was decided to prepare flexural modulus master curves from four point bending beams.

Two alternative trials achieved the project aims by presenting performance benefits in all tested categories, and have been recommended for progression to production and field trials. Additional cost and pavement design analysis revealed that these designs should provide significant cost benefits to Council through increases in pavement life. Through analysis of workability and permeability test results against gradation properties, it was discovered that the quantitative models produced a gravel to sand ratio that could accurately predict the performance of asphalt mixes in the mix design stage, leading to development of two simple gradation models for these performance criterion. These models may significantly reduce testing times and reliance on more expensive testing equipment, providing both time and cost savings for future dense grade asphalt mix designs.

Further analysis and interpretation of the alternative trial results revealed that BCCs Type 3 specification may be inadvertently contributing to design issues. The findings recommended that both gradation limits be raised to promote finer design gradations and that BCC implement stricter requirements for bitumen contents consistent with best practice.

Statistics for USQ ePrint 40891
Statistics for this ePrint Item
Item Type: USQ Project
Item Status: Live Archive
Additional Information: Bachelor of Engineering (Honours) (Civil)
Faculty/School / Institute/Centre: Historic - Faculty of Health, Engineering and Sciences - School of Civil Engineering and Surveying (1 Jul 2013 - 31 Dec 2021)
Supervisors: Nataatmadja, Andreas; Stephenson, Greg
Date Deposited: 08 Sep 2022 03:09
Last Modified: 08 Sep 2022 03:09
Uncontrolled Keywords: pavement materials; surfacing; asphalt mix

Actions (login required)

View Item Archive Repository Staff Only