How to Remove Concrete Grouting

Muriatic acid.

Cheers

Phil Hobbs

This newsgroup is for the repair of electronic devices.

Surely you meant to post this to the repair newsgroup, I think alt.home.repair and just because that newsgroup has turned to mush is not a reason to post an off topic question here.

Michael

HCl is the usual solution. It does attack some stone. Sometimes you can just wet the grout for a while then scrub it off with a plastic scourer wad.

NT

As previously mentioned, use diluted muriatic acid. I did that to my parents patios and walkways many years. It worked just fine but required some extra pre-cleaning and scrubbing to remove some soaked in grease and dirt where I had previously rebuilt an automobile engine. I don't recall exactly what cleaner I used except that it was made for the purpose and supplied by the local hardware store.

If your patio is made from flagstone, I suggest you apply a sealer after neutralizing the acid and letting it dry: After acid cleaning, the surface becomes rather porous and will absorb and trap water, dirt, grease, mold, mildew, shoe scuff marks, etc. I suggest you avoid the "wet look" sealer as it's difficult to keep shiny.

This looks fairly accurate:

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It is a process, and varies with where you live.

Muriatic Acid (follow package directions):

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And a stiff wire brush are your best options. Muriatic acid has a significa nt virtue, the active ingredient (hydrochloric acid) is volatile if not rea cted, and forms salts with many compounds such that it is (relatively) envi ronmentally benign as compared to many other options. It also attacks only the CEMENT portion of the grout, leaving the sand and stone untouched.

Other stuff:

If the walkway is subject to exposure (snow/rain) and you are in an area wh ere there are freeze/thaw cycles, you need to be very careful in how you tr eat the surfaces when you are done cleaning. You may choose to seal the sur face, and if you do so, be sure that it is fully dried (days, at least), an d that you treat the stone and grout uniformly and with the same material. The sealant wants to be a clear, non-volatile material when cured, and abso lutely not anything like Thompsons - which is absolutely worthless in any c ase.

is one of many Silane-based m aterials. Thoroseal is another. But Silane/Siloxane is the gold standard - assuming you have the gold.

So you understand the "why" of it: Most masons these days are poorly traine d in how to mix mortars and grouts. Generally they make the mortar far to r ich, so that it cures (NOT dries) far too hard. When that happens, water pe netration into the stone pavers is greater than what it is to the grout. At which point, during the freeze-thaw cycles, the harder material (grout) wi ll cause damage to the pavers _AND_ if that were not enough, tend to spall in thin layers. So, sealing everything properly will eliminate that problem .

In a warm climate, note that the harder of the two materials will generally fail ahead of the softer material due to thermal expansion and contraction . First it will separate by density, then the smaller sections will start t o crack.

Best of luck with it!

Peter Wieck Melrose Park, PA

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cant virtue, the active ingredient (hydrochloric acid) is volatile if not r eacted, and forms salts with many compounds such that it is (relatively) en vironmentally benign as compared to many other options. It also attacks onl y the CEMENT portion of the grout, leaving the sand and stone untouched.

where there are freeze/thaw cycles, you need to be very careful in how you treat the surfaces when you are done cleaning. You may choose to seal the s urface, and if you do so, be sure that it is fully dried (days, at least), and that you treat the stone and grout uniformly and with the same material . The sealant wants to be a clear, non-volatile material when cured, and ab solutely not anything like Thompsons - which is absolutely worthless in any case.

materials. Thoroseal is another. But Silane/Siloxane is the gold standard

- assuming you have the gold.

ned in how to mix mortars and grouts. Generally they make the mortar far to rich, so that it cures (NOT dries) far too hard. When that happens, water penetration into the stone pavers is greater than what it is to the grout. At which point, during the freeze-thaw cycles, the harder material (grout) will cause damage to the pavers _AND_ if that were not enough, tend to spal l in thin layers. So, sealing everything properly will eliminate that probl em.

ly fail ahead of the softer material due to thermal expansion and contracti on. First it will separate by density, then the smaller sections will start to crack.

During normal operation, damp seeps in from the ground & evaporates from th e surface. If the surface is sealed that evaporation stops, and the stone g ets wetter. Try it for yourself, place 2 stones or tiles onto the earth & c over one with plastic sheet, weighing it down all round. Damp is one of tho se topics on which misinformation abounds.

NT

I am sorry, to realize I did NOT post to my desired net board!! My oops

the surface. If the surface is sealed that evaporation stops, and the stone gets wetter. Try it for yourself, place 2 stones or tiles onto the earth & cover one with plastic sheet, weighing it down all round. Damp is one of t hose topics on which misinformation abounds.

You do not understand how an exterior stone walk is bedded, do you? Done pr operly, there will be 4"- 6" of stone, 4" of sans, then the topping. Which, unless it is concrete, is seldom grouted solid. Not 'never', but seldom.

The entire 'system' moves and shifts with temperature, substrate expansion and contraction due to moisture and so forth. But, even when cut into dense clay, there is little or no need for evaporation through the top. In high moisture conditions, the entire system below the surface will remain damp a nd saturated. Transpiration is both too slow and to imprecise to be of conc ern.

What is necessary is to prevent differential freezing from the top down - t hat is what destroys grouted pavers. And that is why *EITHER* great care is taken to match the grout density to the paver density, *OR* the surface mu st be rendered impervious to moisture. If one is lucky enough to have a mas on trained in the fine art of grouting, then that is the ideal.

Now, if this were to be an indoor application, then you would be absolutely correct - either a vapor barrier must be installed below the top layer (wh ich also becomes a "paper" joint) or the top layer must be left unsealed. N ote that indoor applications are seldom exposed to freeze-thaw cycles. That is why all if this suddenly becomes much more than a casual exercise.

Peter Wieck Melrose Park, PA

You will find a multiplicity of talents herein. I have 40+ years in and around the construction industry from holding the tools to forensic analysis. Others have similar off-label experiences and skills.

Something off-topic, but also relevant to M&R can be refreshing.

Or, not to worry!

Peter Wieck Melrose Park, PA

m the surface. If the surface is sealed that evaporation stops, and the sto ne gets wetter. Try it for yourself, place 2 stones or tiles onto the earth & cover one with plastic sheet, weighing it down all round. Damp is one of those topics on which misinformation abounds.

properly, there will be 4"- 6" of stone, 4" of sans, then the topping. Whic h, unless it is concrete, is seldom grouted solid. Not 'never', but seldom.

Private stone walkways are not usually constructed that way.

n and contraction due to moisture and so forth. But, even when cut into den se clay, there is little or no need for evaporation through the top. In hig h moisture conditions, the entire system below the surface will remain damp and saturated. Transpiration is both too slow and to imprecise to be of co ncern.

that is what destroys grouted pavers.

not just differential freezing, any freeze/thaw cycling when too much water is present causes spalling.

o the paver density, *OR* the surface must be rendered impervious to moistu re. If one is lucky enough to have a mason trained in the fine art of grout ing, then that is the ideal.

ly correct - either a vapor barrier must be installed below the top layer ( which also becomes a "paper" joint) or the top layer must be left unsealed. Note that indoor applications are seldom exposed to freeze-thaw cycles. Th at is why all if this suddenly becomes much more than a casual exercise.

indeed, though indoor construction is not the same as outdoor, except for a small number of historic properties

NT

Couple of things:

Here in the US, especially here in the Great Frozen North, if one does not bed walkways (and sidewalks) properly, their longevity is half-a-hand in years, at best. And if they are grouted, one (1) rough winter will be enough. Bed it, or lose it.

Freezing will always occur from the top down. Thawing, however, may be from either direction based on initial frost depth, nature of the soil(s) and so forth. And why all this is something of a skilled art form. Not to be done willy-nilly.

Peter Wieck Melrose Park, PA

Stone paths bedded direct onto soil last a very long time here. Some from over a century ago are still in service after occasional repairs. Not sure why the difference.

NT

Parts of the Appian Way are still level.

Simple enough questions:

a) Are these paths grouted (mortar between the stones)? That was what initiated the discussion. b) How deep are the stone paths? c) What is the size of the stones? d) Will the climate in your area go from 50F to 4F to 35F to 58F to 24F, include 1" of rain and 2" of snow all in a 96 hour period? That is our forecast this week.

My understanding of the climate in the British Isles is, for the most part, that it is damp but pretty benign given the warming by the Gulf Stream. Sure, Scotland and some of the islands to get some extremes, but not quite the variability.

Peter Wieck Melrose Park, PA

You should use muriatic acid for every 10 swimming pool cleanings, too.

Agreed. My electrical construction experience is only since 1996, but you work around other contractors. The experience is enhanced.

His topic is removal of grout; so the question and replies are on topic. The topic is out of the scope of this group of course.

Regards, ... Peter E.

It is on topic, because sometimes metallic and non-metallic electrical conduit runs through fill encased in concrete.

It is on topic, because sometimes non-metallic electrical conduit runs through fill that is encased in concrete.