From Realtà Mapei n° 38 - 7/15/2024
Ceramic tile grouts play an essential role in the beauty and longevity of tiled surfaces. Often overlooked but crucial, grout serves as the joint filler that holds tiles together, providing stability, preventing water seepage, keeping installations sanitary and adding a finishing touch to overall appearance. In this overview, we will explore the world of ceramic tile grouts, investigating the various types, installation methods, pros and cons, and innovations. Whether you are a specifier, tile contractor or tile enthusiast, understanding the ins and outs of grouting will ensure your tiled projects will stand the test of time. With so many choices in grouts, it may be difficult to select the proper grout for your project needs.
Things change: The tile industry changed, setting materials improved and grouts got better. A couple of newer premium grouts are the high-performance cement grouts and premixed grouts. Both of these types of grouts quickly gained popularity due to their ease of installation, consistent performance and excellent color consistency. While these new grouts are more expensive than traditional ordinary Portland-cement grouts, the cost per square foot/meter to upgrade to premium grouts is less today since the typical grout joint width is now between 1/8” to 3/16” (3 to 4.5 mm) versus the 1/4” (6 mm) average gap width that used to be popular. In addition, the popularity of large-format tile (LFT) designs versus the smaller tile size of the past requires fewer grout lines per square foot/meter of tile due to increased coverage given the smaller joint widths and larger tile designs used today.
Why a high-performance cement grout? The tile industry started to get away from monocottura (single-fired) ceramic tile as porcelain was growing in popularity. Porcelain’s popularity was growing because of increased availability, the fact that it has a much lower absorption rate and is denser than traditional ceramic tile. The low absorption (≤ 0.5%) of porcelain tiles made grouting it different. Traditional cement grouts sometimes got efflorescence and took much longer to cure because the tiles were not taking moisture out of the grout. So, with porcelain tile, there were commonly issues with partially filled grout joints and inconsistent color.
To meet the demanding requirements of ANSI A118.7 Specifications for High Performance Cement Grouts for Tile Installation, most of the high-performance grouts use a calcium aluminate cement instead of or in addition to Portland cement. These grouts offer improved color consistency, no efflorescence and overall superior performance properties, making this the ideal cement grout for porcelain tile. It certainly will not work with all tiles but was a great solution for low-absorption installations. Where these grouts might be difficult would be in high temperatures and with high-absorption tiles, because the grout can partially or rapidly hydrate. For high temperatures you would be best to keep the grout stored in a cool area, to keep the water cold for mixing, and to clean up as you can go... or wait till the temperature cools down. With highly absorbent tiles you would want to wet down the tiles before grouting.
Premixed grouts are relatively new entrants to the market, boasting color consistency, excellent stain resistance and ease of application. The premixed grout category has evolved and grown over the past five years or more. This high-performance grout category cannot effloresce, has no water added, does not require mixing and is faster to install. This type of grout can be formulated with either a urethane, acrylic or hybrid chemistry. These products typically cure by dehydration unlike cement grouts, which must hydrate to cure. As a result, installations in a high-humidity environment can result in a delay in the curing process.
Color consistency is another attribute of premixed grout, as many of the grouts from this category are formulated with color-coated quartz versus free mineral pigments. As a result, pigment washout cannot occur, as the pigment color is bonded to the quartz particle. Efflorescence is also not possible with this grout type, because there is no Portland cement present in the formulation.
Professional installers like the fact that the material keeps when you are done for the day. At the end of the day, you put the lids back on the bucket and seal it well. You open the bucket the next day or even a few weeks away. On reuse, it will match the previously installed area.
MAPEI does not recommend submersion of its premixed grouts, however intermittent water exposure (such as a shower floor) is OK. After more than a decade of work, premixed grouts were added to the ANSI Handbook in 2024. Two new ANSI standards were developed and passed the ANSI committee back in late fall of 2023: For the product standard, American National Standard Specifications for Organic Premixed Grouts for Installation of Ceramic Tile ANSI A118.19, and for the installation standard, The Installation of Pre-Mixed Grout in Tilework ANSI A108.22. With the use of premixed grouts continuing to grow, these standards are a welcome addition to ANSI.
Epoxy grouts offer superior resistance to chemicals and stains, making them ideal for high-traffic areas, manufacturing sites and commercial kitchens. For the industry product standard, epoxy grouts meet or exceed ANSI A118.3 specification, for Chemical Resistant, Water Cleanable Tile-Setting and -Grouting
Epoxy and Water Cleanable Tile-Setting Epoxy Adhesive. The installation standard is ANSI A108.6, for Installation of Ceramic Tile with Chemical Resistant, Water Cleanable Tile-Setting and -Grout Epoxy. Epoxy grout is essentially impervious, with less than 0.1% water absorption. Epoxy is considered the most robust grout category with superior stain and chemical resistance. The installation can be more challenging, as epoxy grouts are generally two- or three-component mixtures that require special mixing, handling and installation at the jobsite. Installation of epoxy grout by a competent tile finisher is not difficult, but it is very different than cement grout. Skin allergies can also occur with a small percentage of installers. This can only occur through direct contact, so it is essential that high chemically resistant gloves up to the elbow be used. Proper personal protection equipment (PPE) is necessary and can help minimize the potential for this reaction. 100%-solids epoxy grout is a thermal-set product that cures by a heat reaction. Epoxy grout has higher abrasion resistance as well as higher bond and compressive strengths than any other grout type.
epoxy grout manufacturers have at least two different types of 100%-solids epoxy grout: A standard or non-industrial epoxy grout, and an industrial-grade epoxy grout. The industrial-grade epoxy is more resistant to more chemicals. Due to the aggressive nature of the chemicals in most commercial kitchens, it is best to grout the tile using a 100%-solids industrial-grade epoxy grout. While in recent years the trend has been narrow grout joints, quarry tile in kitchens is commonly installed with 1/4” (6 mm) joints.
Cementitious-based grout will degrade or deteriorate when subjected to the acidic and harsh chemicals of a commercial kitchen. The best choice for grout in commercial kitchens – which are subjected to hot water and pressure cleaning, harsh cleaners, disinfecting chemicals, fatty acids and no-rinse cleaners – is a high-performance, 100%-solids, industrial-grade epoxy grout meeting or exceeding ANSI A118.3 requirements. Most epoxy grouts are nonsag and are recommended for both floors and walls. For exterior installations of MAPEI’s epoxy grouts, contact MAPEI’s Technical Services Department.
Cement-based grouts are the most common type and have been around for the longest. They are known for their affordability and durability. There are jobsite-mixed sand/cement grouts, factory-blended sand/cement grouts and, the most common today, factory-prepared polymer-modified cement grouts. They are available as sanded for grout joints 1/8” to 1/2” (3 to 12 mm) in width and unsanded for grout joints 1/8” to 1/16” (3 to 1.5 mm) in width. Sanded grouts can be used for most tiles from Saltillo, ceramic, porcelain and quarry tile. Unsanded grouts are commonly used for wall tile, for soft stones (like polished calcium carbonite-based) and for glass tiles. Factory-prepared cement grouts should meet or exceed ANSI A118.6 for Standard Cement Grouts for Tile Installation, and they should be installed following the manufacturer’s directions and ANSI A108.10 for Installation of Grout in Tilework.
Jobsite-mixed sand/cement grout must be pigmented if color is desired. That can be more difficult to control, which is why factory-prepared grouts are so heavily used today. Sand/cement grout also must be damp-cured for proper hydration to occur.
Factory-prepared sand/cement grouts come with sand, cement, water-dispersing agents, pigments and other ingredients. When properly mixed according to directions, this grout is known to be dense, durable, water-resistant and uniformly colored. In the past, installers frequently added a latex admixture instead of water to the grout to get an even denser, stronger, lower-absorption grout with excellent color brilliance.
Today, the most popular cement grout is factory-prepared polymer-modified cement grouts. The polymer is added during production in a water-dispersible latex/polymer powder in addition to sand, cement, pigments and other ingredients. This dry polymer adds the many benefits such as lower absorption in addition to increased bond and compressive strengths. Commercially available polymer-modified grouts have a proven record of performance in commercial and residential projects.
When mixing and installing cement grouts, you must follow the manufacturer’s directions. It is recommended that certain tiles with a porous or rough textured surface, regardless of the absorption value, be temporarily coated or sealed on the surface only, to facilitate grouting. A reasonable amount of thought and planning on the part of the tile setter, before using the selected grouting material, can ensure a satisfactory job.
Proper and consistent mixing of the grout is critical. To ensure uniform performance and color, a quality manufacturer accurately measures the raw materials that go into its cement grout from batch to batch. Likewise, the tile setter should exercise care by measuring the amount of water (or latex additive) used with each bag of cement grout. Considerable shade variations will occur in the same batch of grout if the water/grout proportion varies from bag to bag.
Grout should be mixed with as little water as is practical for application. Excess water will reduce the strength of the grout, may dilute the color, and invites shrinkage, cracking and efflorescence. Mix the grout thoroughly for uniform color and maximum strength.
Extreme care should be used in applying the grout. Tile with high absorption should be wet down with a sponge and water before grouting. Grout should be applied with a rubber float as close to the full depth of the joint as is practical – at least 2/3 of the tile thickness. Setting material that is high in the joint should be raked out, prior to grouting, to ensure uniformity of color of the finished grout joint. When cleaning the surface of the tile after placing the grout, use the technique that calls for the least amount of water possible. Excessive water will weaken the joint and possibly cause pinholes, discoloration and shrinkage cracks. A grout installation can make or break a job.
Ceramic tile grouts may seem like a minor detail, but they play a major role in the beauty and longevity of tiled surfaces. Understanding the different types of grouts, their installation techniques and proper maintenance will ensure that your tile system performs for years to come. Whether you’re selling in a tile showroom, undertaking a tiling project or hiring a professional contractor, a solid understanding of ceramic tile grouts is an invaluable asset for achieving stunning and enduring results.
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