Those are already a thing. This is a proposal to make some use of this already present reality.

PNW has been experimenting with a version of this for a while involving old tires. Rather than let them continue to disintegrate in a landfill somewhere, adding them to newer roads allows the road to withstand freezing weather much better, reducing the need for carbon emitting repairs, increasing road lifespan (and therefore tire lifespan, which in turn reduces microplastic shedding by tires), and gives a second useful life to the plastics we already have.