Is my theory about the fireplace ashes sound or stupid?

We have a rock driveway. At the very end is a concrete apron that leads to the street. A small trench forms on the rock side at the edge of the apron, where the car wheels pass between the rock and the concrete.
We have a fireplace. I surmise that if we take the wood ashes and deposit them in that trench, then wet them down, the weight and pressure of the car driving over the ashes will compact them into something almost solid, like concrete, but not as solid as concrete.
Is this right?