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Concrete Densifiers: An introduction to chemical hardeners and how they work to improve polished concrete
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A polished floor that was score cut, dyed, densified and then burnished using Polish Guard.

Densified polished concrete with custom sawcut graphics.

For someone just starting out in the concrete polishing business, and even for some seasoned veterans, densifiers (aka chemical hardeners) can be a confusing topic. To help offer some clarity, here is my perspective, along with insights from a few other seasoned concrete pros.

Densifier Application

I remember when my friend and colleague, Clif Rawlings, and I presented the first-ever seminar on polished concrete at the 2005 World of Concrete in Las Vegas. Of course, densifiers were discussed. The room was packed to capacity with over 550 attendees, which was a testament to the popularity of the developing market of polished concrete. At WOC seminars, it is mandatory that the speakers present their material in an unbiased format, not promoting themselves or any particular product. A portion of my talk included sharing jobsite experiences involving projects where we used lithium-based densifiers, and I made sure not to product names. At the conclusion of the seminar, we were flooded with questions, including one from a rather pesky attendee who proceeded to read me the riot act, wondering why I barely discussed other types of densifiers and letting me know of the incredible track record of these other products. It all made sense when she handed me her business card. She worked for a large chemical supplier with its own brand of densifiers. I learned a valuable lesson: You can't please everyone, and there are plenty of different types of densifiers to choose from.

Benefits of Concrete Densifiers

The polishing work of Robert Chaney, Antex Western Ltd., British Columbia.

Regardless of the type of densifier you choose, it's important to understand the wonderful features and benefits they offer, such as reduced dusting, higher gloss readings, increased abrasion resistance, and a longer lifespan of the concrete floor. Early on, I remember being skeptical of densifiers. After all, how could this clear liquid that had the appearance of water change the properties of concrete?

I vividly remember the moment our company became firm believers in using densifiers, which was on a large church project. After seeing the results, we have used densifiers ever since. On this 20,000-square-foot floor, I was told the concrete was extremely soft, largely because it had rained on the slab during installation. As a result, we had to apply densifier to the slab before we could even start grinding because it was so soft. After our first grinding pass with 80-grit metal-bond diamonds, we applied a second coat of densifier and kept the surface wet with the material for a minimum of 20 minutes to allow for complete saturation. This hardened the surface enough to allow us to successfully finish grinding and polishing.


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I asked seasoned polished concrete pros Chris Swanson of Colour, Sacramento, Calif., and Robert Chaney of Antex Western Ltd., British Colombia a few questions about the benefits of densifiers. Here are their answers:

The polishing work of Chris Swanson, Colour, Sacramento, Calif.

What are the main benefits of using concrete densifiers?

Chaney: There are a number of benefits, but there are a number of risks too. Densifiers are idiosyncratic. As long as there is free lime present, a densifier will make your substrate harder. My favorite benefit is the ability to lock in a topical color application. Concrete will polish with no densifier, but the durability of the polish is prolonged with the use of a good densifier. The hardness that is achievable is really quite fascinating. Right now, I'm into nano-particulates; they are the wave of the future for so many different products.

Swanson: Floors seem to be much more resistant to staining, easier to clean, and free from dusting. In our experience, densifiers also produce a higher, deeper gloss than when not used.

Do you find that densifiers increase the longevity of your floors?

Chaney: Definitely.

Swanson: We believe that densifiers do add to the longevity of the floors. The surface of our polished floors are harder, easier to clean, and more stain resistant, so we do feel that the densifier increases the durability of our floors.

Densifier Interview

I asked seasoned polished concrete pros Chris Swanson of Colour, Sacramento, Calif., and Robert Chaney of Antex Western Ltd., British Colombia, their opinions on using densifiers. Both men have been in the business for many years and are located in different geographical regions. Some of their work is pictured here.

More work by Chris Swanson, who uses two coats of densifier on his floors to help lock in the color.

During your polishing career, have you always used the same type of densifiers or have you changed and, if so, why?

Chaney: No. I've tried almost all of them, but I'm sure there are a few that I haven't tried. When installed properly with care, any of the sodium or lithium silicate densifiers on the market will do the job; however, we need to make money too. The newer hybrid and nano-particulate technology has helped to save money on labor. How the new densifiers are applied and the coverage varies. I just did 30,000-square-foot floor at a university using a nano-particulate densifier, and though it locked the color in and saved me thousands on labor and material, the apparent added durability that the 20-minute method gives me has me reconsidering or at least doing further testing. There is much debate among myself and a couple of my installers on what gives us the best floor. Is it really saving us money on labor if we have to come back in a year because the sheen is gone in the heavily walked areas? The proof is in the longevity. I know maintenance is also a factor, but the objective is ultimately durability.

Chaney: At Simon Fraser University, Burnaby, B.C., 222,000 square feet of classrooms and offices. At 200 grit, we applied densifier with a 17-inch swing machine using a nylo-grit brush and push brooms. After about 20 minutes, we sprinkled water and agitated some more. Then we vacuumed up the residue and water after another 15 minutes, immediately double mopping behind the freshly vacuumed surface. Fresh water, a good vacuum, foam squeegees, and a guy who knows how to mop corners and edges are absolutely crucial. The ambient temperature and slab temperature play a role in how long I keep densifier on the floor too. If it's 32 degrees Celsius in the day (90 F), we sometimes black-paper the windows and, if possible, apply at night.

Swanson:Ten-thousand square feet.

On a scale of 1 to 10 (with 10 being the highest score), how important is using densifiers on your projects to produce the beautiful work you do?

Chaney: About a nine.

Swanson: Eight. It's not the most important, but it plays an important role.

Related:
Read more articles by Bob Harris.

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