When using millings as RAP, which special precaution is necessary?

Using millings as Reclaimed Asphalt Pavement (RAP) requires careful consideration of several factors to ensure the integrity and performance of the new hot mix asphalt (HMA). The correct answer reflects that all the precautions listed are necessary.

First, ensuring that the millings are free of dirt and clay is crucial because contaminants can adversely affect the quality of the asphalt binder. Dirt and clay can interfere with the adhesion properties of the asphalt and lead to premature failure of the pavement. Clean millings contribute positively to the density and durability of the final mix.

Secondly, it is essential that layers beneath the existing HMA are not disturbed during the milling process. Disturbing these layers can compromise the structural support for the new surface layer. This support is vital for maintaining the integrity of the pavement over its service life, as well as preventing issues such as settling or cracking.

Lastly, stockpiling millings by size ensures that the material can be used effectively in the mix design. Different sizes of millings can have varying effects on the asphalt pavement's performance. Properly managing the size distribution ensures a more uniform and predictable mixture, which is important for achieving the desired properties in the final product.

In summary, adopting all the precautions—keeping the mill