By Cynthia Challener, CoatingsTech Contributing Writer
Demand for concrete for both exterior and interior flooring applications in residential and commercial settings is growing significantly due to the strong health of the construction market, including both new housing starts and remodeling work, in most regions around the world. In the United States alone, over 214 kilotons of concrete was used in flooring applications in 2016, and demand is expected to expand at a compound annual growth rate (CAGR) of 6.3% from 2016 to 2025, according to market research firm Grand View Research. All of that concrete requires protection of some sort, most often in the form of concrete sealers. Much of that concrete is also beautified in some way using decorative coatings designed for that purpose. Consequently, the overall concrete floor coating market was valued by the same firm at $645.9 million in 2016 and expected to grow to $1.15 billion by 2025. Basic epoxy coatings are projected to grow at a CAGR of 6.0% from 2017 to 2025 due to their durability and toughness. The market for polyurethanes used on concrete floors is expected to be worth $268.3 million by 2025 as a result of their excellent corrosion, abrasion, and chemical resistance. Polyaspartics are a third important segment of the concrete flooring market and are used where rapid curing and high performance are required.
ENHANCING THE LOOK OF CONCRETE
Concrete floors—from concrete walkways, patios, driveways, and pool decks to garage floors and concrete interior floors—do not have to retain that original gray look, however. Decorative concrete coatings comprise a special segment of the concrete coatings market designed to add color and/or texture, enabling the transformation of horizontal concrete surfaces to a wide range of finishes and appearances that mimic everything from Venetian plaster to marble and natural stone.
Flooring is a dominant part of a room or space’s color scheme and can dictate the palette or provide the perfect complement, according to Dee Schlotter, PPG senior color marketing manager. Concrete floors are no exception. “Natural concrete is popular and is partly responsible for the prevalent industrial look that is seen today in many commercial and residential designs. The industrial design has evolved to be cleaner and more contemporary, and concrete floor accents in these designs are following suit with subdued colors or sealing with a matte or glossy finish,” she says.
Demand for concrete for both exterior and interior flooring applications in residential and commercial settings is growing significantly.”
The growing number of consumers looking for more sustainable solutions are also driving the growth of the concrete flooring and floor coating markets. “People opting for decorative concrete in their homes are inspired by what they see on social media,” according to Johnnie Elliott, manager of Rust-Oleum’s architect and engineering team. Popular choices include the use of decorative chips and metallic coatings to create unique looks. Exterior applications remain the largest part of the market, though. “Exterior decorative applications are growing as homeowners look to extend the inside to the outside. They want the same decorative look outside as they expect inside, and they see the value in protecting concrete,” he adds. The natural state of concrete is very relevant, especially in multifamily spaces, as people want a seamless look from inside to the outside of the home. Agrees Schlotter, “It’s becoming clearer in today’s design that homeowners want to bring the outdoors in—with plants and natural elements. We are also seeing the ombre look on concrete, which creates a haphazard, imperfect look,” she says. For contractors, ease of use and repeatability are the key decision criteria when choosing a partner, according to Elliott.
Both old and new concrete can be modified with decorative coatings. Application of decorative coatings is, in fact, a way to revive old concrete and avoid the need to remove and replace it. “Most often, decorative coatings are applied to substrates that pose a problem to remove or are too expensive to remove/replace,” observes Elliott. In addition to ceramic tile, he points to stamped concrete patios as an idea for reviving with decorative coatings, which avoids the need to re-pour and stamp, color, and stain. “Applying decorative coatings to floors previously covered with carpet is another way building owners can introduce industrially modern, creative, and unique looks that are easy to clean and will far outlast their predecessors,” he notes.
OVERLAYS AND STAINS
There are two major categories of decorative concrete coatings: overlays and stains. Overlays are applied on the top of the concrete floor. They include polymeric coatings such as acrylic, epoxy, and polyurethane systems formulated in a range of colors. They generally are composed of a mix of cementitious and acrylic materials, but some products are based on natural crushed limestone or recycled solid surface fillers. Overlays are used to add both color and texture and are typically applied in thin layers, most often using a trowel, but in some cases by spraying. Some come pre-mixed except for the desired liquid color, while others are sold as powders that require mixing with colorant and water/solvent.
Stains penetrate the concrete. Acid stains are typically a mixture of water, hydrochloric acid, and acid-soluble metallic salts. They are available in approximately 10 different earth tones that can be diluted to create a range of shades. They react with the lime in the concrete, generating a mottled appearance that is determined by the composition, age, and condition of the concrete. Water-based stains are typically acrylates designed to penetrate the concrete and deposit pigment particles in the pores of the floor. Because they do not react with the concrete, the color of an applied water-based stain is the same as that in the bottle. The range of colors is also much broader than acid-based stains. In addition, water-based stains do not present the hazards associated with acid-based systems.
Both stains and overlays can be used on new concrete. For worn concrete areas, resurfacing with an overlay provides numerous options for adding colors, stamped patterns, and textures. Staining and stenciling are appropriate for older concrete that remains in good condition. In addition to the desired appearance and the state of the concrete floor, the appropriate decorative coating will be dictated by the application conditions (time, temperature, location, etc.), the conditions to which it will be exposed, the desired life expectancy for the coating, and the cost limitations.
PREPARATION OF CONCRETE SUBSTRATES
Whether the concrete floor is old or new, its surface must be in reasonably good condition. Decorative coatings applied to existing floors with extensive cracking or gravelly surfaces will not last. In these cases, it is better to replace the floor—or portion of the floor—that is damaged prior to applying any type of coating. It is also crucial that floors in appropriate condition be properly prepared prior to coating application. To achieve both the desired appearance and a durable decorative coating, dirt, old peeling paint, and other materials should be removed first. In addition, different types of decorative coatings may require different preparation methods or techniques. Choices include sand or water blasting or grinding or cleaning with special cleaners and/or a mild acid wash. The goal is to remove the unwanted materials and open the pores of the concrete. Minor cracks should also be repaired, and the floor patched and leveled as well. Compatibility with the decorative coating system should be considered when selecting the materials used for any of these repairs. Even new concrete requires preparation, such as the removal of curing compounds and any adjustment of the surface profile/roughness as dictated by the decorative coating to be applied.
All decorative coatings applied to concrete floors require protection of some kind. Concrete floors, particularly exterior surfaces, can be exposed to impact, abrasion, chemical attack, and thermal shock. A concrete sealer should be applied over the top of the stained or overlayed surface to reduce wear and tear and extend the lifetime of the decorated surface. Different sealers are available depending on the level of abuse expected for a given concrete floor.
MEETING TODAY’S CHALLENGES
One of the biggest challenges for formulators of decorative concrete coatings today is the development of products that reduce the application time and enable faster return-to-service. “Our biggest challenge is providing the fast return-to-service that customers are coming to expect while also providing enough working time for contractors to ensure a consistent result each time,” Elliott says. Rust-Oleum is working closely with its key suppliers to develop custom resins and co-develop products that address this challenge. Offering a primer/basecoat in one product, for example, provides a quicker return-to-service, with floors being completed in one day. Longer working time polyaspartic coatings with a rapid cure time are another. “These products also enable same-day return-to-service, which is key in most industrial and light commercial environments,” comments Elliott.
“One of the biggest challenges for formulators of decorative concrete coatings today is the development of products that reduce the application time and enable faster return-to-service.”
Environmental regulations, particularly those relating to volatile organic compound (VOC) content, can create some difficulties as well. “VOC restrictions and certain chemical shipping and use regulations have had some effect on product development. These regulations have limited the shipment to and use of some decorative concrete coatings (e.g., acid stains and traditional solvent-based coatings) in certain areas, which has driven the development of alternative products. In addition, as the industry becomes more heavily regulated, costs to the end user continue to rise,” observes Elliott. Rust-Oleum continues to push the limits of the technology to offer contractors the best products that are the most repeatable. One notable example is expansion of its portfolio of nonisocyanate-based products that still offer true UV stability, which will provide contractors with the ability to offer their customers very unique finishes for all exterior concrete surfaces, according to Elliott.
Rust-Oleum has two primary focus areas—working closely with contractors to ensure that their needs are met and listening to the market trends regarding floor coverings as a whole. “Most decorative concrete coatings can mimic a look or trend, so keeping up-to-date on these developments will be key to our success moving forward. Our goal is to always have products/finishes that will wow the consumer,” Elliott states.
CoatingsTech | Vol. 15, No. 10 | October 2018