Which of the following is not a requirement for successful recycling of asphalt pavement?

The successful recycling of asphalt pavement involves several critical factors that ensure the quality and integrity of the recycled material. Among these, the factors such as the age of the asphalt, the cleanliness of the reclaimed asphalt pavement (RAP) materials, and the proper grading of those materials are essential.

The age of the asphalt can influence the characteristics of the mix; older asphalt may have different properties compared to newer material, which can affect how it blends with new asphalt binder. Additionally, the cleanliness of the RAP materials is crucial, as contaminants such as dirt, excessive asphalt binder, or other foreign materials can adversely affect the bonding and performance of the recycled asphalt mix. Proper grading ensures that the sizes of the RAP aggregates are compatible with the new materials to maintain the structural integrity and performance of the asphalt.

In contrast, while environmental conditions during milling can impact the efficiency of the milling process, they are not classified as a direct requirement for the recycling of asphalt pavement itself. Factors such as temperature or humidity might influence operational aspects but do not inherently determine the success of recycling in terms of material composition or performance. Thus, this makes the environmental conditions during milling the outlier in this context.