How to Work with Decorative Concrete
November 12, 2013
Flooring contractors looking to branch out into new avenues of commercial work may think about entering the decorative concrete business. However, properly and professionally creating a long-lasting and eye-catching decorative installation in concrete requires more than just throwing some dye on the floor or running a flooring machine over the surface until it achieves a mirror finish. FCI spoke with several experts in the decorative concrete field to learn some best practices and tips for those just starting out in the segment.
The first thing to know about any concrete that is to be stained or dyed is its history, according to Todd Scharich, decorative concrete specialist for the American Society of Concrete Contractors. “Floors that have been cured or sealed with not allow dyes to properly penetrate the concrete or allow acid stains to chemically react,” he said. “If the floor is to eventually be polished it is critical to also know the levelness and hardness of the floor.” Scharich recommends that contractors perform a test in a discreet location but on the same slab that will be receiving the decorative treatment.
Stains and Dyes. Concrete stains can either be reactive (acid stains) or nonreactive (water-based polymer stains). Both systems have their pros and cons. Reactive stains will form a permanent chemical bond with the concrete, but since they are derived from natural mineral salts, the color choices are limited. However, according to Scharich, they offer one-of-a-kind looks. “Reactive stains will yield unpredictable but beautiful results when used properly, nearly always producing a variegated or marbled type of finish.”
Nonreactive stains, on the other hand, offer a larger selection of colors and more consistent finishes, but they require a mechanical bond to the concrete. Also, “nonreactive stains lack the rich, deep and translucent qualities that acid stains offer,” Scharich stated. To open up the surface of the concrete when using nonreactive stains, an acid wash is often used. This should never be done with reactive (acid) stains, as it will destroy the ability of the stain to chemically react with the concrete. “Acid stains work best on hard troweled floors,” Scharich noted.
Concrete dyes are also nonreactive, and since they penetrate deep into the concrete’s pores, they are nearly as permanent as acid stains. Dyes require a non-sealed, open floor in order to properly penetrate the concrete. Solvent-based dyes tend to be more uniform in color, while water-based dyes produce a more variegated finish, Scharich said. Dyes are usually not UV stable without a protective coating or finish, so “be sure the type of dye chosen, and the finished coating or treatment, will withstand the UV exposure your project will face,” Scharich added.
Polishing. An additional step in decorative concrete installations, for a fully finished look, is polishing. Scharich said the word “polishing” as it is usually used is actually a misnomer, as it implies that polishing is done in one step, when it is actually a three-step process. He prefers the term “concrete processing.”
“Concrete processing is far more difficult than just simply putting abrasives on the machine and running them across the floor,” Scharich warned. “The process is actually very technical, mixed with many variables that are outside the control of the contractor, which can lead to variable results and unmet expectations if not performed by a trained or experienced professional.”
The three steps of concrete processing are grinding, honing, and then finally, polishing. “Throughout the full processing steps, a liquid densifier will be used to help strengthen the floor and bind any previously applied stains or dyes into the full concrete matrix,” Scharich explained.
When grinding, a 50 grit or below resin abrasive is used, bringing the surface to little or no sheen with a flat appearance. If the floor is not level, this step will also expose various levels of sand and aggregates. “This is the biggest area of contention in problem projects,” Scharich said. “Specifications should clearly define a good mix design for a polished floor, as well as the floor levelness that is required for the concrete finisher to meet.”
Following the grinding process, the floor then needs to be honed, using resin abrasives from 100 to 400 grit. This will bring out a matte finish with some reflection. Finally, for polishing, the contractor needs to move up systematically from 800 grit resin abrasives to 1,500 or 3,000 grit. “This ultimately creates a polished surface that has clear, mirror-like reflection and a seemingly glass finish,” Scharich said.
Before jumping into these three steps, contractors should first understand how much PSI the concrete can withstand. Scharich noted, “Not knowing whether the concrete is low PSI (2,500 and under) or higher PSI (3,500 and above) will dramatically alter the tooling and amount of time needed on the floor. A high PSI concrete placed flat with power trowels will generally offer the polishing contractor a much better chance of creating the desired results.”
He also cautioned not to rush the job. “Bypassing any of the consecutive steps of a full polish will leave scratch marks, inconsistent exposed aggregates, un-levelness, and varying sheens.”
Best Practices. Before doing any type of decorative concrete work, first the surface needs to be prepared, stressed Bob Seman of Seman Flooring in Washington, Pa. An Ardex LevelMaster Elite installer, Seman said one thing holds true in any installation: “You can’t cut corners.”
“The best practice I can give for decorative concrete is repair any cracks that aren’t going to be a part of the finished design, prep the floor, and hook up with a company like Ardex or someone who does this type of work and practice ahead of time,” Seman noted. “All of these different toppings and decorative products are very sensitive. You have to be conscious of air flow, air conditioning, drafts under doors – all of these factors will make a difference in how the decorative treatment looks when it dries. For these types of projects, you need experienced and detail-oriented help.”
He also said it is important to set realistic expectations. “Things will move and crack out of everybody’s control. Sell that ahead of time,” Seman stated. “Set the expectations correctly.”
While not for everyone, those who do get into concrete find it to be a vital part of the business, Seman added. “Concrete just brings so much energy to the business. I go to World of Concrete and I’m like a kid in a candy store. I look at a warehouse floor that I’ve polished, and it looks like a million-dollar floor.”
Engraving. Another option worth mentioning when working with concrete is engraving. This is the act of remodeling existing, cured concrete by cutting patterns and textures into the surface. “Engraved patterns often simulate building materials such as brick, tile stone, pavers or a variety of graphic elements, including geometric patterns with straight, circular or serpentine lines and custom designs,” said Darrel Adamson, founder and CEO of Engrave-A-Crete.
Before bidding on the job, evaluate the surface on which you’ll be working. This means using a moisture meter to make sure the moisture levels aren’t too high, testing the hardness of the concrete and testing for sealers. “A soft concrete surface will cause failure of the stain and sealers every time, no exceptions,” Adamson said. “If sealer is already present, it must be removed before any stain is applied.”
When setting expectations with the customer, be sure to let him or her know that every slab colors differently and won’t exactly match the color chart. “Test in an inconspicuous area and get customer approval before progressing,” Adamson noted. “Sealers also vary in glossiness, so have actual samples of stained and sealed concrete for customer approval.”
Engrave-A-Crete carries a full line of tools for engraving concrete, including abrasive diamond blades, sand blasting, shot blasting, micro-rod impaction and reciprocating styluses. After the concrete is engraved, the installer should clean the area, touch it up as needed, and apply a protective sealer/clear coat. However, the most important step, according to Adamson, is surface prep.
“Surface prep is extremely important,” he said. “It’s a hard and dirty part of the job, but it is essential to the success of the project.” Prep requires removing any contaminants from the surface, and either power washing exterior surfaces or scrubbing interior surfaces with a floor machine equipped with a black pad or sanding screen.
Adamson also offers this advice: “After a bit of experience, installers mistakenly believe they’ve mastered the process and get sloppy with their work or cut corners. It’s important to remember that every concrete slab is unique and will react to products differently, and every pattern is a challenge that deserves the installer’s full attention.”