The first thing i would try is a sandblaster.
Removing tar from concrete wall.
Test it for effectiveness.
Next apply the mixture to the tar carefully and let it sit for a few minutes.
There actually seems to be a dearth of information on efficient ways to do this.
Follow the label s recommended ratio.
Scrape the tar off with a drywall knife.
The oil or bitumen from the tar will leech into the cement so the longer the tar remains the deeper the stain.
Check the label carefully before you open the bottle making sure.
To clean the tar from your concrete floor with muriatic acid first put on all of your safety gear.
If you are lucky a tool rental shop may have a small sandblasting kit that works off of an air compressor used by carpenters.
Steps to remove the tar.
I would not use them as the fire hazard is so extreme.
Dilute the acid to the desired strength using the label as your guide.
The sooner this is accomplished the better.
When diluting always add acid to the water.
Review the package s instructions carefully then dilute the acid by adding it to water in a sturdy bucket.