Korie asked: How do I remove tar from fresh concrete? We are undergoing a renovation at our home. We poured a new concrete slab (to accommodate hydronic heating lines), put up the walls and the ceiling, which is also the base for the deck above. The deck needed to be waterproofed as well (to accommodate an ice melt system) and the workers spilled foundation tar on the new concrete slab. We are planning to til this slab, but need to remove the tar without doing damage to the concrete! Any suggestions would be helpful. Thank you!
Tar 
is probably the last substance you’d expect to come up easily from any surface, let alone concrete, but you’re about to be pleasantly surprised. You can achieve professional results with relative ease by following this advice for cleaning virtually any mess from concrete. A word of advice: Before you begin, make sure you read the label directions and wear protective gear, including eyewear, gloves, and clothing.
You Will Need:
- Muriatic Acid
- Eye protection
- Thick rubber gloves
- Protective clothing
- Stiff bristled brush
- Water
- Bucket
- Plastic scraper
- Towel
Steps to Remove the Tar:
- Put on all of your protective gear before you begin working with Muriatic acid. Check the label carefully before you open the bottle, making sure you adhere to all safety procedures and precautions.
- Dilute the acid to the desired strength, using the label as your guide. When diluting, always add acid to the water. NEVER add water to acid.
- Start with a weaker solution and strengthen it if necessary. (You’ve reached the right strength when it bubbles when coming in contact with the tar.)
- Cover the tar with the acid mixture.
- Wait a minute or two for the acid to work on the tar.
- Begin scrubbing with the stiff brush. When it becomes difficult to remove, add a new coat of acid and allow it to work for a moment before scrubbing again. Scrubbing may cause the acid to splatter, so keep pets away and wear clothes you don’t care about. Keeping your mouth closed is also a good idea.
- As the tar becomes loosened from the concrete, scrape it off with a plastic sraper or wipe it off with a towel. Use a towel to wipe off the scrub brush as needed also. Use a towel you can throw away. Disposable terrycloth cleaning rags from a hardware store are very useful in this situation, and a pack of 50 or more is only a couple dollars.
- Repeat until the tar is completely gone.
- Rinse thoroughly with fresh water.
- Follow acid label directions for disposal of excess acid during clean up.
Additional Tips and Advice
- Muriatic acid is available near the pool supplies in most home improvement or hardware stores.
- Store acid out of reach of children, following all manufacturer’s recommendations and safety precautions for the product.
- Muriatic acid is actually used by contractors to clean and prep concrete before projects, so you can expect an excellent result from the use of the product.
Has anyone had experience in removing burned-on wire insulation from concrete?
Easy to say.