Concrete Sealers

I remember twenty years ago consulting on the Chiquita Banana high rise building in Cincinnati Ohio.  All of the windows were covered with hard water spots. Which were from the concrete.  You see acid rain soaks into concrete as if it were a sponge.  All concrete and brick has pores.  Brick, concrete, and lime stone are alkaline.  So acid rain will react with these materials literally breaking them up.  The minerals that are leached from the pores are then carried away by the rain and run down the glass.  Once there they are deposited on the windows when the sun comes out and dries the rain.  These mineral deposits or hard water spots will now lock into the glass pores.  Next the window cleaner comes along to clean the windows.  But cannot remove the spots.  The windows have been severely stained and are in need of restoration.

But here's the point.  Restoring the windows to full clarity is NOT the most important matter. Stopping the concrete from leaching minerals with a good quality sealer IS.  Why?   Because if these panels are not properly protected with a sealer they will ultimately need to be replaced.  When I was working with the company that hired me I was told about another building on the other side of town that was currently having their concrete panels replaced because the building was crumbling!  If your high rise window cleaning company is going to price the glass restoration, you should also price the sealing of the concrete or brickwork.  Which should also help to prevent the hard water spots from coming back.  It could also represent another twenty thousand bucks in your pocket. Another reason why the window cleaner should also seal the concrete is he will make sure the sealant doesn't run down over the glass.  Further, cleaning the windows every six months will tell how well the sealant is working.

I will never forget looking at a problem job for a window cleaner out west.  The windows were covered with concrete sealant.  The building owner couldn't understand the difficulty since he could scrape off some of the sealant with his fingernail. To which my friend replied, "Well then use your fingernail on the entire building"!  Obviously this is a rather large problem if you don't have a liquid chem that will dissolve the sealant and wash it away.  Kind of like when someone opens a can of Pepsi on a window.  A good cleaner and strip washer is usually all you need.  But concrete sealant is much more difficult to remove.  Here is the reason.  First let me copy some technical information regarding the chemistry of concrete sealers from the Wikipedia.

"Topical Sealers: Topical Sealers can provide visual enhancement as well as topical protection from stains and chemicals. They require a dry, clean surface during application to gain adhesion. Topical sealers may alter the coefficient of friction which can make substrates slick when wet – a condition that can be remedied by adding anti-skid materials. Life span is generally 1-5 years, although high-end epoxy/urethane systems can last significantly longer.

Penetrating Sealers: Penetrating sealers can be applied to dry or damp surfaces and should be properly matched with substrate porosity in order to effectively penetrate the surface and react. The chemical reaction bonds active ingredients within the substrate blocking surface moisture. Penetrating sealers generally do not significantly modify substrate appearance or traction. Lifespan is generally 5 years or more.

Acrylic Resins: Acrylic resins form a topical film membrane on the substrate surface. They are available in both water-based and solvent-based formulas, affordable, and generally simple to apply. They are well known to increase perceived visual enhancement (sometimes described as a “wet look”) and can provide good UV protection for colored substrates. Despite being the softest and least lasting of the major sealer categories, price and convenience make acrylic resins a very popular choice for decorative concrete such as stamped concrete and exposed aggregate. Acrylic resins are also commonly used as curing agents for new concrete, and many comply with ASTM C309.

Epoxy/Urethane Systems: Epoxy/urethane systems are also topical film membranes. They share many of the same characteristics as acrylics, but the performance levels and life span are superior and commensurately more costly with more complex installation requirements. Novolac epoxies are particularly noted for chemical resistance and acid resistance. High-end urethanes are known to be extremely abrasion resistant. Epoxy/urethane systems are frequently used in demanding applications such as factory floors, garage floors, and restaurants, and water-based versions are often used to seal concrete countertops. Epoxy/urethane systems are generally applied only to fully cured existing concrete, although certain epoxy products can comply with ASTM C309.

Silane: Silane is the smallest molecular compound of commonly available penetrating sealers. Chemically, Silane forms a covalent bond within porous masonry that clots surface pores. Silane is known to be hydrophobic and oleophobic and will only wear away if the concrete surface itself wears away. Noted for very low viscosity, silane is frequently used for sealing dense concrete, such as parking decks, concrete facades, and dense brick. Silane is generally applied only to fully cured existing concrete.

Silicates: Silicates are another small molecular compound ranging from premium lithium silicates to economical sodium silicates. Chemically, silicates form calcium-silicate hydrate crystals which can densify concrete surfaces and be burnished to develop a polished appearance. Silicates are known to be hydrophobic and oleophobic and will only wear away if the concrete surface itself wears away. Noted for crystallization, silicates are frequently used for polishing concrete floors popular in large format retail outlets. Silicates can be applied to new and existing concrete, although they do not comply with ASTM C309 as a curing agent.

Siliconates: Siliconates are moderate-size molecular compound. Chemically, Siliconates form a repellent cross-linking membrane barrier within the surface of porous concrete and other masonry. Siliconates are known to be hydrophobic and oleophobic and will only wear away if the concrete surface itself wears away. Noted for extreme water repellence and stain repellence siliconates are frequently used for sealing exterior concrete such as roads and driveways, tilt-up walls, porous brick, and porous stone. Siliconates and organo-siliconates have also been shown to be affective as curing agents for new concrete and certain products can comply with ASTM C309.

Siloxane: Siloxane is the largest molecular compound of commonly available penetrating sealers. Although not highly reactive, chemically siloxane forms a bond within porous masonry that clots surface pores. Siloxane is known to be hydrophobic. Noted for large molecular structure, siloxane is frequently used for sealing exterior concrete, porous concrete block and porous brick. Siloxane is generally applied only to fully cured existing concrete.

In summary, all major concrete sealer chemistries can have valuable and practical applications. Topical sealers generally require higher application standards and maintenance, but the decorative appeal and potential stain and chemical resistance can make them a superior choice for many applications. Penetrating sealers should be matched with substrate porosity for long lasting low maintenance water repellence and freeze/thaw protection."

You might have inferred from this information the reason why it is so difficult to remove certain penetrating concrete sealants from glass. The ones I have highlighted in blue.  These go through a curing process.  The polymers will crosslink to one another and the glass.  You see glass has what are called free oxygen atoms at the surface.  These are the atoms that the sealant polymers also react with or bond to.  This is why it is impossible to remove all of the sealant with a razor blade, steel wool, or even very powerful organic solvents.  The only way to completely clear these sealants from windows is to remove a very thin layer of glass with a polishing compound.  The window must be polished with an optical grade superabrasive suspended in the most powerful organic solvent.  The solvent should also be water miscible.  This makes it very easy to remove after soaping and squeegeeing.  You will know you have done the best job possible by fogging the clean window after.  If there is ANY residue left at all, the fog will show it up.  Even if the window appears crystal clear on a bright sunny day it can still be holding onto residue.  This makes for an easy demonstration when soliciting a job.  Just buff out a small spot by hand and fog it with your mouth.

I have created just such a specialty compound for removing concrete sealant rundown from glass .  It is a SKRUB transformer product.  And is described in my one page pdf e-letter Raw Ingredients.  For 35 dollars.  You can buy the ingredients yourself.

Written by Henry Grover Jr.
henrygroverjr@gmail.com

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