In Hong Kong, the design of roadbase material adheres to a recipe approach, following traditional British practice. This entails specifying the aggregate grading envelope, bitumen quantity, and grade within the bituminous mix. Such recipes are typically based on historical experience and established construction practices. However, many countries are now shifting towards specialized design mixes tailored to specific site and design conditions.
The recipe-based specification of bituminous materials presents several limitations. Firstly, the traffic and climate conditions of newly constructed roads may deviate from those upon which the recipe was originally based. If adjustments are needed, determining and evaluating the necessary modifications can be challenging. Secondly, recipe specifications can pose difficulties for site engineers when assessing the impact of minor non-compliance. Lastly, the recipe mix may not always be the most cost-effective solution, as it does not necessarily account for specific site conditions that could influence material choices and quantities.
These drawbacks underscore the need for a more adaptive and context-specific approach to roadbase design. While the traditional recipe approach provides a reliable starting point, it may not always yield the most optimal or economical solution for every project. Embracing specialized design mixes allows for greater flexibility and customization, ensuring that the roadbase material is tailored to the unique demands of each individual project.