Hi marcus and welcome to our forum
in short yes you can spray pave over existing slate look concrete. First though you must grind the existing surface to remove as much of the impression as possable and also to remove the concrete sealer that would have been applied to the concrete. Then prior to applying the base coat you may have to trowel over the area to mask any remaining impression.
We have just finished a job like this in Melbourne and i will be posting photos on our gallery
http://www.supremeresurfacing.com.au/photos/index.php i will also post some here as well. The job came up very well and the customers were happy with the result.
Cheers
David
