No, the problem you have is you will have pockets of ash under the clay even if the top is hard. You might be able to mix some sand and mix in with water and compact, be you will have to go all the way to the bottom of the ash. The best would be to pick up a little of the existing soil when you...
Ksths2 I think I can help you out some on your fly ash or bottom ash problem. There is a difference between bottom and fly ash. From your description I would say you are refering to fly ash. Is it tan in color? Is it purely a fine material like 1/8" minus(no pieces bigger than 1/8"). I live...