What is the recommended size for nominal maximum aggregate in asphalt mixtures?

The recommended size for nominal maximum aggregate in asphalt mixtures is commonly around 19 mm. This size strikes a balance between providing good particle interlock for stability and minimizing the amount of void space in the mix for effective asphalt coverage. A nominal maximum aggregate size of 19 mm allows for proper distribution of the materials, ensuring the mixture adheres well while providing adequate strength and durability.

Using smaller aggregates, such as 5 mm, might limit the structural integrity and load-bearing capacity of the pavement. Conversely, larger aggregate sizes, such as 25 mm or 50 mm, can lead to a rougher surface finish and can complicate the compacting process, ultimately affecting the smoothness and performance of the asphalt surface. Therefore, 19 mm is widely accepted and utilized in various asphalt paving applications to optimize performance characteristics.