Peter Wagner, Director of Supporting Products Development for Curecrete was recently published in the January 2017 issue of Concrete Construction/Concrete Surfaces magazine. Addressing the recent innovations in concrete grinding and polishing, Wagner examines three-step methods and testing procedures currently on the market.
*The full article is provided below with text as published by Concrete Construction/Concrete Surfaces magazine.
THREE-STEP METHODS AND TESTING PROCEDURES: Great Tools When Used Correctly
Is it the New Math or did someone forget to tell contractors that preparation counts as a step when polishing concrete floors? And are we being subjective in our testing methodology?
A number of manufacturers (of which we are one) provide an accelerated grinding and/or refining and polishing process for polished concrete. These processes aren’t for every floor or contractor. There have been questions regarding shine longevity, especially from consultants who want to vet a process or technique before recommending it to clients.
I’ve become a believer over the past couple of years. However, I’m concerned about misrepresentations and with what I see as attempts to judge subjectively the benefits of a particular system.
” I’m comfortable using the T-meter and Ra for objective, not subjective, verifications.”
You don’t achieve a polished concrete floor by simply polishing; there’s an initial step(s) in the grinding/prep stage. Any finish is achievable with an accelerated process. Whether your process is two, three, or four steps depends on floor hardness, floor flatness, and the customer’s expectations.
When we at Curecrete Distribution Inc. refer to our three-step process, we’re describing a salt n’ pepper appearance finished through an 800 dry resin. The final touch, as we recommend on all floors, is a 3000 maintenance pad run dry with a burnisher to remove any residual resin and show the true floor. This is a true three steps.
Photographs from top to bottom: 1 (paint), 2 (stainless steel), 3 (plastic), and 4 (polished concrete with a distinction of image (DOI) of 73.4 and gloss @ 60o of 58.5) were taken less than 1 inch from the surface. Visually, to me, there’s no correlation, or uniformity, between these surfaces.
A deep aggregate finish generally starts with a lower metal to gain the desired aggregate exposure, adding a fourth step. So whenever you see “once the floor is prepped,” “if first cut is made with 50 grit then you may have to add,” “floors should be prepped prior to step #1,” or “a diamond tool is necessary if the client wants more aggregate exposed” in manufacturer instructions, you’re adding a step. Do the math: that’s four steps.
As for longevity, our KickStart Clarity Enhancer achieves distinction of image (DOI) readings from the high 50s to low 70s after more than six months of daily forklift traffic. Speaking of DOI, now is a good time to address the concept of subjectivity versus objectivity.
USE THE RIGHT TOOLS THE RIGHT WAY
Three- (or four-) step systems are only as good as your ability to read the floor and how well you use the tools available to read the floor.
This isn’t the first time I’ve felt compelled to write about subjectivity versus objectivity. My 2009 Concrete Décor article questioned the practice of requiring that certain gloss readings be met as part of a specification. My article’s premise rings true today with ST-115 and roughness average (Ra): When used correctly, the T-meter is an objective tool that benefits specifier, owner, and applicator. When used incorrectly –subjectively – it fails us all.
As I wrote the article, the late Bill Jones, former president of Substrate Technology Inc., shared that he likes installers to provide gloss unit (GU) as a qualitative number to shoot for but not necessarily the endpoint one will always achieve. Using GU readings as a guideline rather than an absolute allows the installer to renegotiate – or walk away if the number isn’t obtainable. Without doing a test you don’t know what’s achievable. As you read on, all I ask is that you have an open mind.
Using GU, DOI, and profile (Ra) readings objectively, as tools to assess a floor before and during the grinding and polishing stages, is intelligent. Using them in specifications as a way to keep the competition at bay is misdirected and ultimately hurts the industry.
The September Concrete Surfaces article titled “The Numbers Don’t Lie” refers to “the industry’s first foolproof method” for polishing concrete. While the numbers may not lie, I believe they can be quite subjective.
In the November 2014 issue of Durability & Design (D&D Magazine), Chris Bennett, then with Husqvarna, wrote “Taking the Measure of Polished Concrete”. “What’s Good Enough for Steel” headed a section on why the T-meter was the tool for “quantifying the geometric irregularities of a mechanically refined floor at various levels” and that it “provides a way to describe the exact means and methods to produce the floor the architect and owner asked for.”
I ask, how can you promise a floor will consistently meet expectations throughout the pour? Does a method exist that verifies, without a single doubt, that the number of readings required provides statistical verification? That the required number of reads are taken as required?
James McArdle was involved in creating 3M’s Trizact System. Now owner of Stone Sole Associates, a research and development laboratory for architectural, construction, and manufacturing clients, he says, “Ra testing is very positive, but not definitive, in its ability to provide indicative information.”
FATAL FLAW: UNREALISTIC EXPECTATIONS
Andy Bowman, who chaired the 17-person Concrete Sawing & Drilling Association committee that drafted ST-115 in 2011, is quoted in the Concrete Surfaces article as saying, “You simply meter the floor behind every pass of the grinder or polisher to see what your Ra is.”
Manufacturers that Promote Three-Step ProcessesGMI Engineered Products LLC (Bluffton, Ohio): CRMX 3-Step Concrete Polishing System
Curecrete Distribution Inc. (Springville, Utah): KickStart Clarity Enhancer
Green Umbrella (Buffalo, N.Y.): GHP Process
Superabrasive Inc. (Hoschton, Ga.): Lavina 3-Step Concrete Polishing System
US Abrasives (Minneapolis): EZ Polish System
The elephant in the room is that concrete doesn’t fit the same pattern as three materials it’s being compared to. Steel, plastic, and paint are manufactured under controlled conditions. With concrete, each pour, each slab varies from the previous one; there’s no consistency in mix design, placement, or finishing. You can no more compare concrete to steel, paint, or plastic than you can to ceramic or porcelain tiles that are deemed rejects or seconds if they don’t meet a uniform expectation. The fact that all four industries use abrasives in some manner doesn’t make it correct to share the same tools for measurement.
Jim Cuviello, a polisher and industry expert who first looked into Ra profiling in a January 2011 ForConstructionPros.com article, notes that pits, pores, micro fissures, aggregate, and degree of consolidation around aggregates can produce a wide range of readings. Concrete pours are affected by which ingredients are available regionally, site conditions, weather conditions, and the personnel skill.
Variables that Affect Polished Concrete Quality
- Human error
- Mix design
Without an exact mix design, exact placement, exact finishing, exact equipment and tooling, and personnel experience and training, you cannotpolish concrete to the same exacting standards as those of the steel, plastic, or paint industries. It doesn’t matter whether you’re talking about a gloss meter, DOI, or T-meter; when misused, they’re detrimental to our industry. If used objectively, they can help foster our industry’s growth.