Analysis of the Practical Impact of Mixing Pavement Thickness Design Methods: Study on Rigid Aircraft Pavement Concrete Strength in Australia

Rigid airport pavements are a critical part of the Australian airport pavement inventory. The thickness design of rigid airport pavements in Australia was previously based on Australian developed charts and a conservative characteristic concrete strength, but in recent years this has changed to reliance on the software FAARFIELD provided by the US. Australian designers have used FAARFIELD in combination with the historical and conservative definition of concrete strength. That conflicts with the intended use of a less conservative Australian concrete strength value for inputting into FAARFIELD. The unintended consequence of this change in Australian practice is an additional 44 to 74 mm of concrete slab thickness, depending on the aircraft type, subgrade support, and concrete strength used. This additional thickness costs an additional AUD 185,000 to AUD 429,000 and 154,000 to $\mathrm{333,000}\mathrm{kg.}{\mathrm{eCO}}_2$ for a modest $100\times 100\text{-}\mathrm{m}$ rigid airport pavement development. This additional financial and environmental burden is not justified, and Australian airport pavement designers should adjust their thickness design calculations to avoid this unintended overdesign in the future. This example also serves as a lesson regarding the potential consequence of mixing elements from different systems for pavement thickness design.