Getting cement stains off of composite decking

Leoskeys · 06-04-2021, 08:59 AM

Hi, we had our chimney re-done(brick to stone), and the Mason did a beautiful job. However, he failed to properly shield our Trex composite deck so there are cement stains all over. We’ve tried various cleaners liked “wet and forget” and Valspar deck cleaner. We’ve obviously used a pressure washer too. Alas, none have worked!
Google didn’t provide any new insight so I turn to the collective mind of the forum for suggestions.
I tried to attach photo, not sure if it worked.

WinnisquamZ · 06-04-2021, 09:32 AM

If it was me, I would try a wire brush and go with the grain. Unfortunately, it’s mortar. Has acids. Once you get off what you can with the brush you may test a latex exterior stain on those areas. Oh course, you match the stain to the deck.

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The Real BigGuy · 06-04-2021, 04:00 PM

Found this on the web:

https://www.fiberondecking.com/blog/...osite-decking/

Also saw something about using Maria tic acid. If you have an extra piece of decking you can do a test to see if muriatic damages it.

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DickR · 06-04-2021, 05:04 PM

Mortar contains portland cement, and thus is alkaline, not acidic. So it does make sense that an acidic solution would react with it. Muriatic (hydrochloric) acid might do it, but even vinegar, a weak acetic acid solution, might work.
https://cretedefender.com/the-importance-of-ph/

TiltonBB · 06-04-2021, 08:17 PM

Muriatic acid will definitely make it bubble and liquify. That is what the concrete companies use to clean the drums on concrete trucks. It works well and does not damage the paint on the trucks. The question is what it will do to the deck. Try it on a sample piece or the underside first.

WinnisquamZ · 06-04-2021, 08:29 PM

When using it to clean I would start with a 10 parts water to 1 part muriatic acid and go from there

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06-04-2021, 08:59 AM	#1
Leoskeys Senior Member Join Date: Feb 2015 Location: Lakes Region Posts: 147 Thanks: 131 Thanked 27 Times in 21 Posts	Getting cement stains off of composite decking Hi, we had our chimney re-done(brick to stone), and the Mason did a beautiful job. However, he failed to properly shield our Trex composite deck so there are cement stains all over. We’ve tried various cleaners liked “wet and forget” and Valspar deck cleaner. We’ve obviously used a pressure washer too. Alas, none have worked! Google didn’t provide any new insight so I turn to the collective mind of the forum for suggestions. I tried to attach photo, not sure if it worked. Attached Images

06-04-2021, 09:32 AM	#2
WinnisquamZ Senior Member Join Date: Dec 2016 Posts: 1,890 Thanks: 192 Thanked 593 Times in 398 Posts	If it was me, I would try a wire brush and go with the grain. Unfortunately, it’s mortar. Has acids. Once you get off what you can with the brush you may test a latex exterior stain on those areas. Oh course, you match the stain to the deck. Sent from my iPhone using Winnipesaukee Forum mobile app

06-04-2021, 04:00 PM	#3
The Real BigGuy Senior Member Join Date: Apr 2004 Posts: 1,108 Thanks: 108 Thanked 410 Times in 244 Posts	Found this on the web: https://www.fiberondecking.com/blog/...osite-decking/ Also saw something about using Maria tic acid. If you have an extra piece of decking you can do a test to see if muriatic damages it. Sent from my iPhone using Winnipesaukee Forum mobile app

06-04-2021, 05:04 PM	#4
DickR Senior Member Join Date: Apr 2008 Location: Moultonborough Posts: 735 Thanks: 4 Thanked 254 Times in 166 Posts	Mortar contains portland cement, and thus is alkaline, not acidic. So it does make sense that an acidic solution would react with it. Muriatic (hydrochloric) acid might do it, but even vinegar, a weak acetic acid solution, might work. https://cretedefender.com/the-importance-of-ph/

06-04-2021, 08:17 PM	#5
TiltonBB Senior Member Join Date: Feb 2005 Location: Gilford, NH and Florida Posts: 2,895 Thanks: 643 Thanked 2,153 Times in 900 Posts	Muriatic acid will definitely make it bubble and liquify. That is what the concrete companies use to clean the drums on concrete trucks. It works well and does not damage the paint on the trucks. The question is what it will do to the deck. Try it on a sample piece or the underside first.

06-04-2021, 08:29 PM	#6
WinnisquamZ Senior Member Join Date: Dec 2016 Posts: 1,890 Thanks: 192 Thanked 593 Times in 398 Posts	When using it to clean I would start with a 10 parts water to 1 part muriatic acid and go from there Sent from my iPhone using Winnipesaukee Forum mobile app