Hi,
Its a bit of a silly question but I thought I might be able to find some help here. In my garden where I park my car it has stones laid but they have that white powder stuff on them so everytime i park up it covers my tyres in white powder

Does anyone know if there is anything I can get to get rid of this white stuff off the stones? They have been in the garden for a couple of years now and no mattter how much rain goes on them when it drives its still there

.
Cheers
Dan