On the face of it, there are different concrete finishes for different purposes, so knowing your finish and your purpose is imperative for having a successful project. Also you need to take into consideration is that in many instances there is usually an architectural specification for larger projects and you may not be able to choose your methodology, so knowing both the traditional ‘no guard’ process and ‘concrete with guard’ process will be useful so you don’t miss any opportunities that come your way.
Polished concrete is growing in demand as both home builders and commercial engineers & designers are responding to the public’s desire for something architecturally beautiful, yet resilient and wear-resistant. There really isn’t anything else quite like polished concrete to fit that bill.
When done right, a concrete floor with guard compared to naturally shiny concrete floor can look almost identical. So, why would anyone choose one over the other? What are the features and benefits of each method? This article will attempt to shed light on this matter.
What is a concrete guard and where should it be used?
First off, a concrete guard is not a jan-san ‘wax’. It looks like a wax, it’s applied like a wax, but it is in reality a semi-topical, semi-permanent acrylic finish that usually has a chemical component in it, (such as lithium), that allows it to bond to concrete. Guards are not thick and gooey such as a high solids jan-san wax that has 25% solids. Guards are semi-topical and are meant to soak into the concrete but leave a thin protective layer on the top. You aren’t supposed to build up guard with multiple coats, like with a wax.
Guards need to be applied thin because concrete is very hard and almost impossible to scratch, so if you have a thick layer of guard protecting the floor the guard is going to be ‘sacrificed’.
A sacrificial coating is a coating that is meant to be put in harms way. If you drag something across a guarded floor or spill a corrosive chemical, then the guard will take the brunt of the abuse and not the concrete itself.
So, if the concrete is virtually scratch resistant, why apply a guard at all if you can make the concrete shiny and attractive without it?
Using a guard adds a measure of oil/water resistance to the concrete surface. The thin layer on top clogs the concrete pores and oil/water spills will stay on top and not soak into the concrete. This makes guarded floors very popular in supermarkets and box stores. Of course, there are impregnating concrete sealers that are not semi-topical and will repel oil and water too, but in many cases on large projects you are at the mercy of what the architect or builder specifies.
Guard also protects against acid/corrosion stains. Impregnating sealers will prevent surface intrusion of liquids, but they will not prevent a chemical process from occurring. If acid comes into contact with concrete it will eat the calcium and leave a permanent etch mark that will need to be ground out with diamond abrasives. (further in this blog we have an example of this type of etching and how we fixed it)
Also, concrete guards are also known as ‘stain guards’. Some architectural specifications call for decorative stains to be put onto the concrete. The stains sit near the surface and the guard protects the color. If something is then dragged across the floor the guard is sacrificed on behalf of the color stain. In high traffic areas the guard needs to be ground down dull with mild abrasives, then recoated and then re-burnished.
What is the argument against using guard?
It’s not the guard itself that the traditional ‘non-guard’ concrete guys rail against, it’s that some folks in the industry use guard to ‘jump up’ a shine. For instance, some may take a concrete floor that is matte finish and then apply and burnish a guard to make it look like it is polished concrete, when instead all you have is a shiny coating on top of dull/matte concrete. There is nothing wrong with doing that as long as the client knows that this is the process that is being done, but when a shiny guard on dull concrete is ‘sold’ us delivering a polished concrete floor, then you get drama…lots of drama…
Here is a case study where concrete guard is being used in an acceptable manner.
Case study: A concrete floor in a supermarket has been neglected to the point where even when clean, it looks dirty. One of my clients was called upon to provide a solution.
This floor has seen better days. It now always looks dirty because of ingrained soil particles embedded in the guard and the way scratches in the guarded floor reflect light to the human eye. Why did the original contractor apply a guard? Well, you can see the solid stain that is beneath the guard. Guards are meant to guard the color stain with a protective coating so if something is dragged the color isn’t compromised. If no guard was applied, then the topical stain would quickly wear into a traffic pattern and trying to fix a wear pattern in the actual stain is not fun because usually you need to grind it all off and start all over again. if you want the stain to match.
The only way to properly deal with scratched and damaged guard like this is to scrape it down and re-apply, but be careful not to scrape far enough to compromise the color stain. (anymore than it has already been compromised…bleah) Since there is is a danger of scraping away the stain if the grinding process is too aggressive you may want to sacrifice the speed of using an aggressive grit and a dry process for the finesses of using a lighter grit and a wet process.
In this case study we used the STI Spin-1 Pad System, a 50lb. weighted plate and the Mytee HS 300 300 RPM single speed burnisher. For the purpose of this demo, we added some water to the floor, but not too much. This supermarket is almost always open and even when it’s closed there isn’t enough time to empty the shelves from the food products or mask everything off. The safe course is wet and slow, and since I’m a big chicken, we took a little longer and avoided potentially contaminating several thousand dollars of cold cuts, fish and cheese products. (I’d like my salmon fillet with less concrete silica dust please…) Bleah.
Fortunately, the STI Spin-1 Pad System can be used wet or dry. These pads a natural hair and have a special diamond encrusted coating embedded on the ‘business’ side in which the diamond abrasives are held in place to be used on both guarded and unguarded concrete.
These pads from STI are really nifty, but you need to know how to order them. They are called Spin-1 pads. I don’t know why. There is no Spin-2 pad system, Spin-3 pad system blah-blah-blah. (you get the idea) What there is, is a 5 step system or levels of the Spin-1 pad system that are both color coded and numbered. The Spin-1 #1 pad is the coarsest and aggressive, while the Spin-1 #5 pad is for light polishing. You can use them with a high speed burnisher up to 3000 rpm or with a weighted or non-weighted machine at lower rpms. (walk behind jan-san scrubbers too!)
There are too many variables for each floor to determine what number disk and what equipment you would need to accomplish any given task on a floor, so order all 5 so you are covered for any situation. These pads also come in a wide variety of sizes. Just remember to ask your rep for Spin-1 pads, specify the size and the grit level 1-5. Since I’m partially color blind, I won’t even go into the color code system. Even in the picture above, the color I see is ‘bleah’.
The picture belows shows what the floor looks like after the guard is ground down and prepped for re-coating.
Yes, it looks ugly, but we aren’t done yet. The Spin-1 pad #3 did it’s work and scrapped the floor smooth. Even though the light reflects ugly, if you run your hand over the floor you’ll find it smooth to the touch because the blemish marks are not surface residue from the previous guard on top of the floor, but empty voids in the concrete from years of wear exposed by removing the guard. From this point, the only way to get the floor shiny again naturally, without using a guard, would be to keep grinding the concrete down to make the floor smooth and the voids disappear. That is not on the menu tonight. because the client does not want to re-stain the floor. Thus are using a guard to make the floor shiny again.
We applied Sentinel All Surface Floor Guard to this abused concrete floor. This is a great all purpose guard from our friends at Sentinel products.
Once the guard is down and it looks even, let it dry to the touch and then sit for a bit, especially if you did wet grinding and there is some moisture still potentially evaporating from the floor. In a large job site production situation you probably won’t get backed up and have to stop and wait for the floor to dry after wet grinding because you’ll have industrial fans going and a large, industrial surface area etc, but when doing a small demo spot you never want to rush it and risk fogging the guard through water evaporation through the forming acrylic membrane.
We burnished the Sentinel 404 guard with the 300 rpm Mytee HS 300 and a Spin-1 #4 pad dry. (for such a small spot, we didn’t worry about airborne contamination) For a larger scale area, using a 3000 rpm propane burnisher will be more efficient, but be sure to use a vacuum attachment on your polishing machine to ensure that you do not contaminate the atmosphere, especially if you are in an area where you could harm people or contaminate food. Most high speed burnishers have a portal to place a hose attached to a vacuum.
This case study was a success. We achieved all our goals. We were able to scrape away the scratches of the old guard without harming or fading the stain underneath. We did not needlessly contaminate the atmosphere with dust and junk by doing a dry grind. We applied new guard to the floor and burnished it, making it hard and shiny, which gave us an attractive, slip resistant surface that would repel oil stains and prevent bacteria and germs from penetrating into the pores of the concrete and forming colonies of ‘smelly bleah’ that could lead to indoor air pollution from the off-gassing of the bacteria. Finally, we were able to get this process accomplished within a reasonable budget.
Case study: A busy multi-million dollar resort has an unsealed, dingy looking sidewalk in the front that is stained from years of drink spills, gum being mashed into the concrete pores and foot traffic from incoming parking lot foot traffic tracking asphalt oils onto the concrete contributing to the overall ‘bleah’.
While consulting on this job, I suggested doing a good, smooth scrape on the surface of the sidewalk and then coat it with just enough guard to glaze the sidewalk, but not make it too shiny. This plan worked out because they wanted to color sections of the sidewalk with a dark stain, similar to what show in the previous case history in the supermarket.
This sidewalk had a lot of ‘bleah’ going for it. We were going to fix that…
This job required a measure of discretion. We wouldn’t be able to pull up with a large propane powered unit or even a large 220v grinding unit because of the noise a gas powered generator would make. Additionally, with larger, faster moving equipment there is too much drama in dealing with the close proximity of resort clientele, some of who would be entering and exiting the facility in various states of inebriation. The facility didn’t want us building large wooden barriers to cordon off the work area, they wanted us working behind easy to move stanchions and lots and lots of yellow ‘danger’ tape. (which everyone knows is not drunk proof…)
Here we used a heavy floor machine from Hawk. It’s heavy, sturdy, easy to use and operates on 110v electric. The abrasives we used are STI MG2 System (again with the numbers) #3 diamond abrasive disk followed by the STI MG2 #4 abrasive disk. The #3 disk is like the equivalent of a 200 grit diamond grit. We wanted to take a layer off without penetrating the cream layer too deep and exposing the aggregate.
We did wet…again. Even though dust wasn’t an issue outside, the noise was, so we made a little slurry and pushed it aside and then used a slurry vac intermittently to remove the material.
This sidewalk hasn’t been this clean in years. Bleah. This is after 2 steps. #3 and #4 MG2 STI abrasives and a good cleaning.
We put the topical stain on an area of the sidewalk first…
We then added two coats of Sentinel 404 to both areas, but we weren’t done yet.
We used the Mytee 300 RPM HS 300 to do a light burnish without a weighted plate. We wanted to harden the area and buff out any imperfections from mopping down the guard on a sidewalk in the sun. ( Note: I would not have recommended doing this demo in direct sunlight because of potential issues with both the dye and the guard, but the hotel requested it during the day. We did warn them that there we potential cosmetic imperfections by doing this in direct sunlight and they said they were ok with that.)
Ok, now it’s done. The hotel asked when they could walk on it. We told them it was ready for the public to do their worst…(and believe me, they did…)
The facility was impressed that we used equipment that could plug into their 110v external electric outlets, we did not make a lot of noise, no one complained about smells or chemicals. We hit a home run and my client got the job.
NOW WE START TALKING ABOUT NATURAL SHINE CONCRETE WITH NO GUARD…(thank you for your patience…)
Ok, we’ve seen to case studies where using guard was practical, what about the benefits of going ‘au’naturale‘
Guard applied to concrete is ‘semi-topical’ which means that there is a coating on top. This coating is not impervious, it will wear and it can scratch. Naturally polished and densified concrete that does not have that layer of guard on it will not scratch like a guarded floor, (if at all) That being said, there are many guards on the market, and many techniques for using it, but if someone says that they have a guard that performs like naturally polished concrete then they are probably overselling their product.
This sample area was polished shiny the ‘natural way’ and then a section was guarded, so we have guard on top of shiny concrete.
After burnishing the guard and letting it cure I then unscientifically dragged something heavy across it and vola! Had we not put the guard on the surface, we would not have a scratch.
The area where the concrete was shiny and there was no guard was unaffected by the heavy equipment being dragged across it. If you look closely, from this distance you can see the scratch in the guarded area. (it doesn’t look like such a big deal from when you aren’t right on top of it…) Repeatedly dragging equipment across the bare shiny concrete will eventually wear it down, but not as quickly or badly as the shiny guarded floor.
Does this mean that guarded concrete surfaces are inferior? Nope. just different. If I took an acid based diet Coke and spilled it across both areas I’d have a nasty, permanent etch mark/stain on the unguarded, natural portion while I could let the Coke sit on the guarded area for a few days without too much drama. The acid in soft drinks will eat the calcium in concrete but will not eat the acrylic of the guard.
Here is an example of an unguarded concrete floor with acid etch stains.
This garage floor was stained, but not guarded. Stain by itself will not seal a floor, and eventually whatever acid drama was happening in this garage, (this is Las Vegas and I have a strict ‘don’t ask, don’t tell’ policy…) came into contact with the calcium in the concrete and we had a big fat mess.
Yeah, that’s ugly…or really beautiful if you are into abstract art.
These acid stain are no problem if you know how to fix them…
In this case, cost was a factor, so I consulted with my client and suggested that we do on step of diamond grinding to get rid of the acid stains, then guard the floor, then burnish the guard.
Normally you want to put guard on top of shiny concrete, but since this was not the Taj Mahal my client was able to please the property manager and score a nice job repairing acid stained garage floors.
You can still see the scratch marks from the diamond abrasives, but the property owner was ok with that. They wanted to pay for as few steps as possible. If they really wanted to save money they should have sealed/guarded it properly the first time.
So where is it practical to prep concrete floors cosmetically without using guard?
Glad you asked…
Large, industrial surfaces…
Ugly, old epoxy…bleah…
Polished to a natural sheen, not too slippery-shiny, but very easy to maintain. Sweep it, mop it, forget about it. (photos courtesy Kevin Hawthorne)
I don’t know what the end use is for this floor. A museum maybe? But this environment is the perfect place to put down an invisible, impregnating sealer and avoid scratches that will interfere with the artistic reflection of light. (photo courtesy Kevin Hawthorne)
Is it possible to misuse guard in an industrial situation?
Here is a big time fail for a large, industrial surface. This stadium facility was finished with an architectural epoxy terrazzo floor. Epoxy terrazzo is synthetic, thus there is no calcium carbonate and it will not etch. Also, because of it’s synthetic nature, epoxy terrazzo is naturally slip resistant no matter how shiny. Think of it as real hard plastic. Can it stain? Sure there are micro pores that need to be cleaned out if the contractor didn’t seal the air pockets during the installation process using an STI groutpan, but the plastic itself will not stain. Sooooooooo…why did they guard it?
I’m just there to fix the floor, not pass judgement. (I’m not a judgey guy…)All I know is that because the contractor finished with a guard, they made a footprint and scratch nightmare that gave the maintenance crew fits. Can you imagine being the cleaning manager in charge of removed scruffs and scratches from several thousand square feet of bleah on a nightly basis??? Can you imagine what the building management was thinking after being sold on a low maintenance, scruff resistant epoxy resin terrazzo floor and instead getting a high maintenance scruff attracting guarded floor? Bleah.
I was called upon to consult on this job. I said we need to grind off the guard and start shining the floor up from scratch. The facility owners didn’t like that assessment, but the truth is the truth.
This job took 8 steps. We had to grind through the ooey-gooey-sticky guard to get down to dull, bare, epoxy terrazzo and then work back up to a bright shine. The STI Mg2 pad system is 8 steps and we had to use every one of them to fix this floor.
The result was a slip resistant, scruff resistant, scratch free shine. Sure, after a big concert there are plenty of scruff marks, but those marks are from shoe material leaving matter behind on the floor, not damage to the surface. When the maintenance crew uses plain water, a red pad and a standard jan-san walk behind they get back to the epoxy terazoshine instead of having to do multiple steps of polishing to grind the damage out of the guard. There is going to be periodic maintenance on the floor due to all the traffic, but only using the higher grits of the MG2 pad system, not the lower ones.
Can badly scratched guard be repaired?
Yes. The standard way to polish guard is to use a diamond encrusted pad with a high speed burnisher. That’s POLISH, not scratch removal. Sometimes the guard damage is beyond what a diamond encrusted pad can do because of deeply embedded damage.
Here we have a guarded floor in a test area in our warehouse. It started off nice and shiny, but after some months the shine wore away and scratches appeared. We used the Durashine System and the OnFloor Durashine machine to fix it. The nifty unit is 110v and perfect for those hotel or casino lobbies that need to be shined up, but you can’t bring in your propane or 220v monster grinder. It’s 110v whisper quiet and every concrete maintenance polishing company should have one in their arsenal. You can use hard Durashine diamond abrasive pads 50 grit to 3000 or diamond encrusted pads like the STI Spin-1 pad system.
What make the 110v electric Durashine System by Onfloor unique is that it will let you use hard diamond abrasive goods in lieu of the diamond encrusted natural hair pads so you can more aggressively polish both guarded and natural shine floors. Pictured here are the Durashine high speed diamond pads.
While you can put a shine back onto damaged guard, be prepared to put down another coat if there are any areas where the guard has worn all the way thru to the bare concrete.
Architectural shiny residential floors do not necessarily need to be guarded. An impregnator will sit below the surface and thus the floor sans guard will not scratch from pet toenails, moving furniture, skateboards ect.
This floor is an example of a floor covering rip out and instead of replace the floor covering the existing concrete underneath was polished.
This floor was also dyed in the process of polishing. Another blog will discuss the art of dyeing concrete floors.
Polished concrete in homes is very artsy and progressive…
Yep. Now that the concrete is polished you can put down an exotic rug down, maybe even change the rugs out for different seasons. There is a lot of seasonal interior design work you can do with a nice concrete floor and a rotating set of fine carpets. Notice how the cracks and areas where the aggregate is closer to the top add to the personality of the floor and are not treated as undesirable imperfections. No two concrete floors are alike. You can also see a faint outline where the tiles were previously on the floor before they were demolished. It’s like art. No guard, no scratches, no problem. (photos courtesy Ken Fellows)
Are there any circumstances in which it may be appropriate or advantageous to guard a concrete floor in a residential setting?
Sure. Here is a floor where the owner wanted a topical stain and a sacrificial coating of guard would be needed to protect the color.
The homeowner wanted more of a solid color on the floor instead of the typical translucent acetone based dyes. If you use a penetrating translucent dye then you can use impregnators, but if you put down a topical stain, then you are guarding the floor.
Under some circumstances, if the floor didn’t need to be demolished and was in good enough shape, you might not even need to grind it at all, depending on the exact circumstances.
A client of mine had the ugliest garage floor in town. Bleah. He asked me for some help to get is looking spiffy again.
We cleaned it real good with an acid etching solution (to open the pores) and then put down a topical stain with an ordinary pump sprayer.
After you use a pump sprayer for a job like this, you should never use it for anything else ever again. You can never really get rid of all the dye out of the sprayer after you’ve used it this way.
Use a bristle broom to move the dye around a little bit and obliterate the spray patterns. The same advice goes for using a broom like this, either keep it as part of your concrete tools arsenal or throw it away. That dye gets everywhere and into everything.
After the dye is dry, put down one or two layers of concrete guard to protect the dye. If you want to make it shiny, then you can burnish it, but if a semi-gloss guard finish is acceptable then you can leave it be.
What made this a ‘no grind’ situation is the surface integrity of the floor. It was already flat and mostly smooth, just really, really stained. Now it’s smooth and attractive, almost too attractive for a garage floor…
Did you learn anything?
So, are you a natural shine grinder who hates on the contractors who may do a few less mechanical steps with abrasives and then guard? Are you a blow and go ‘guard shiner’ who sells the job to the client as if they are going to get a natural concrete shine and then give them a cheaper guarded shine with hardly any mechanical work being done?
As this blog shows, there is more to concrete surface prep than merely making the floor shiny, we need to access the needs of the client and give them the floor that will best suit their needs. Therefore, we shouldn’t hate on an honest contractor who correctly represents himself as to the procedures he uses to accomplish the client’s desired look.
The concrete surface prep industry is very segmented. Part of the concrete industry is involved in new construction and installing new concrete floors in both commercial and residential settings. Then there are the contractors who do remodels. They are the ones who come in and remove/demo a floor covering and polish the concrete they find under what they demo, and then there are the maintenance contractors who repair the existing floor to it’s original shine, as opposed to attempting to change the overall nature of the floor.
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3 thoughts on “A Basic Study in The Field of Concrete Polishing, ‘Using Guard or Not’. Features and Benefits of Both.”
nice job show me know
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Love it. Thanks.
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