Tool for removing concrete roof/patio coating/material

I'm going a small job where we're scraping off what looks like a painted coating that was put over a previous layer of roofing material - the latter looks like cork of some sorts.

We're removing it down to the substrate which is concrete. We've been using scrapers which has been working but it's a tough job.

I wanted to know if a pneumatic scraper or electric oscillating tool would be faster? I imagine the electric oscillating tool wouldn't be as efficient as a pneumatic tool.

I don't have any pictures so I hope my description was clear. Please let me know if it's not.

Suggestions?

 

Not sure of the volume of material to be removed, but you could buy or rent an SDS hammer and purchase scraping tips. Makes easy work of scraping from a hard surface.