Ash as sub base for a driveway

[pombozo]

Hello,

I’d be grateful if anyone could offer some advice. I’ve been renovating my house which was built in the early 1900’s.

One of the nasty jobs I had to do was remove the dense black mortar and lime render mix covering the internal walls. I believe the mix was made from a coal ash from the mining industry abundant in the area at the time.

I removed around 3 tonnes as the wall covering was so thick in places. I left this on site in rubble bags with the intention of using it as a sub base for a new hard standing. I'm about to lay a gravel drive using a gravel stabilisation system.

I’ve read the info on pulverised fly ash as a bedding layer. Would anyone advise on using the mortar mix I have saved as hardcore or bedding? It seems like a good mix of fines and chunks and I think it would compact quite well.

The concern I have is that it might not be strong enough as the larger chunks can be broken up quite easily. Another concern is that it might be fertile and would encourage weed growth if it were too close the the surface.

Any advice would be much appreciated.

Thanks.

[dig dug dan]

If its the stuff that is referred to as clinker, I have seen it under pathways many a time, nut not on a drive.
there is a suppllier round here who is mixing power station ash with type one as a chepper alternative, its ok when its dry, but once it gets wet, it turns to mush, so I wouldnt bother

[pombozo]

Thanks for your reply Dan. I think you're right. Since your comment I left an open bag out in the rain and it does turn very soft. I think it's time to bin it!