What device is responsible for carrying the asphalt mix back to the spreading screws?

The device responsible for carrying the asphalt mix back to the spreading screws is the slat conveyor or flights. This choice is correct as slat conveyors are specifically designed to transport materials horizontally and can efficiently move the asphalt mix from the mixing area to the spreading screws. These systems utilize a series of moving slats or flights that help maintain the material's flow while also controlling its movement, ensuring a consistent supply to the spreading mechanism.

While conveyor belts could also transport asphalt, they typically do so over a longer horizontal distance and not specifically designed for the type of delivery needed in paving applications. Augers are used primarily to convey materials through rotating screws, which could work for asphalt, but they are more associated with mixing and distributing granular materials rather than transporting asphalt mix back to a specific point like the spreading screws. Vibrators are utilized mostly to reduce friction or help materials flow more easily, but they do not transport the asphalt mix themselves, which makes the role of the slat conveyor or flights crucial for this application.