So your idea was to use the asphalt as the floor to the shed? Can you locate the shed elsewhere? For an 8x8 shed, you don't really need a frost-proof foundation. That small a building is a rigid enough structure that settling or frost heaving won't damage it, and you don't need a 'real' foundation. Typical construction would be on grade, either on piers, timber framed (rectangular wooden frame sitting on gravel), or on skids.
IMO - you can just build it and not anchor it. My Dad built a 9x12 shed like that on a brick patio, with no real anchoring and ordinary stick-built construction. I took that shed down a decade later and moved it to another town, and except for the termite damage it's still a fine shed. Make the sill wide enough so that it doesn't sink in to the tarmac in hot weather.
