Bulletin #9

Revised August 15, 2005

Materials For Grouting Ceramic Tile

The Tile Council of America, Inc. Handbook for Ceramic Tile Installation lists and describes the current materials used for installing ceramic tile, for setting as well as grouting. MMSA designed the following Grout Guide Chart to help the industry select the proper grout for each installation.
American National Standards have been written for the installation and testing of all Grouting Materials. These are as follows:
1. ANSI A108.6 Installation of Ceramic Tile with Chemical Resistant, Water Cleanable Tile-Setting and Grouting Epoxy.
2. ANSI A108.8 Installation of Ceramic Tile with Chemical Resistant Furan Mortars and Grouts. 1
3. ANSI 108.9 Installation of Ceramic Tile with Modified Epoxy Emulsion Mortar and Grout.
4. ANSI A108.10 Installation of Grout in Tile Work.
5. ANSI A118.3 Chemical Resistant, Water Cleanable Tile-Setting and Grouting Epoxy.
6. ANSI A118.5 Chemical Resistant Furan Mortars and Grouts.
7. ANSI A118.6 Ceramic Tile Grouts
8. ANSI A118.7 Polymer Modified Cement Grouts
9. ANSI A118.8 Modified Epoxy Emulsion Mortars and Grouts.

The ANSI A108 specifications are concerned with the installation of the tile and materials selected. The ANSI A118 specifications describe the testing procedures used to determine the quality of the materials used. In other words, the A108 specifications describe procedure for satisfactory installation, while a product or material that meets or surpasses the requirements of an A118 specification is deemed a quality product. Highlights of the ANSI A108.10 are as follows:

1. This specification describes the minimum requirements for grouting ceramic tile.
2. Grouting and curing shall be performed at temperatures between 60°F-90°F.
3. Uniform curing conditions shall be provided or maintained at the jobsite.
4. Before grouting, all tiles must be firmly set, all paper and glue removed from face of mounted tiles, and all spacers, strings, ropes, or pegs removed.
5. Machine mixing of grout is preferred to assure a uniform blend. To prevent trapping air bubbles into the prepared grout, use a slow speed mixer, maximum 150 RPMS.
6. Dry blending of an entire container of Commercial Portland Cement Grout, Dry-Set Grout, or the powder portion of a Latex-Portland Cement Grout is recommended prior to mixing the material with water or Latex. For large areas, dry mixing several bags together, in a power mixer, will also insure a more desirable or uniform cured joint.
7. The water or latex additive used for mixing with the dry grout shall be measured accurately.
8. All grout joints shall be filled with grout material a minimum of two-thirds (2/3) of the thickness of the tile used.
9. All grout joints shall be uniformly finished.

The following general statements and helpful hints are designed to aid the industry in producing a satisfactory grout joint — the most critical part of the entire installation.

1. Commercial Portland Cement Grouts, often colored, have been used successfully since the early 1940’s — followed by Dry-Set and Latex-Portland Cement Grouts. All of these grouts usually contain Portland Cement, graded aggregate, water dispersing agents, plasticizers, and, for colored grout, colorfast pigments. The aggregate used varies from very fine for glazed wall tiles to coarse for mosaic and vitreous tiles, depending upon the width of the joint used. It is recommended that certain tiles that have a porous or rough textured surface, regardless of the absorption value, be temporarily coated or sealed on the surface only, to facilitate grouting. (Please refer to MMSA Bulletin No. 12 for specific details.) A reasonable amount of thought and pre- planning on the part of the tile setter, before using the selected grouting material, can assure satisfactory job. Caution should be exercised in grouting soft glazed tile to prevent the aggregate from scratching the surface.
2. An evaluation of the Setting Bed is recommended. Portland Cement Mortar Setting Beds that are excessively wet or that contain cement with high concentration of calcium carbonate are prone to cause efflorescence. A curing period of 4 to 5 days prior to grouting will virtually eliminate the problem of efflorescence, which is the largest source of complaints for dark colored grouts. Some organic adhesives or mastics set by the evaporation of solvent or solvent-emulsion present in the adhesive. This solvent release can be harmful to both the satisfactory curing and color of grouts. A minimum 24-hour curing period for the adhesive is recommended before grouting ceramic mosaics, longer if possible. Larger tiles would require a longer cure period.
3. Proper mixing of the grout is mandatory. The manufacturer for uniform performance and color, batch to batch, measures the raw materials that go into a bag of grout accurately. The tile setter should exercise equal care by measuring the amount of water (or latex additive) used with each bag of grout. If less than a full bag is prepared or mixed at one time, dry mix the entire bag first to prevent a color variance in the finished product (pigments and fine aggregate have a tendency to settle while being transported). 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, cracks and efflorescence. Mix the grout thoroughly for uniform color and maximum strength. Machine mixing is highly recommended over mixing by hand. Slow speed equipment (less than 150 rpm) is suggested to avoid entraining air bubbles into the grout. Latex additives are often used with Commercial Portland Cement, Sand- Portland Cement, and Dry-Set grouts. They tend to help prevent fast drying, aid the Portland Cement hydration and reduce the need for the 72 hour damp curing by ANSI Standards. Consult the literature of both the grout manufacturer and latex manufacturer to insure compatibility.
4. Extreme care shall be used in placing the grout. Tile with high absorption should be wet down with a sponge and water, or by fogging prior to grouting. An ambient temperature of 60°F + will give best results. 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. High ridges of setting bed adhesive or mortar should be raked out of the joint, prior to grouting, to insure uniformity of color of the finished grout joint. Some manufacturers recommend dry dusting of the grout and a final rub out with a coarse nylon pad or burlap sack. Rubber or plastic tile spacers, where used, are to be removed prior to grouting. Check the manufacturer’s directions for specific details.
5. When cleaning the surface of the tile after placing the grout, use the driest possible technique. Excessive water will weaken the joint and possibly cause pin-holes, discoloration, and shrinkage cracks. Clean up with a cheese cloth pad and/or terry cloth towel is recommended for small areas. Large areas could involve dragging the surface with a damp blanket, or using a power floor scrubber with a nylon pad or short nap piece of carpet. Rinse or clean the cheesecloth, towel, or blanket frequently. An acid wash is not recommended. The reasoning is that the acid will dissolve the Portland Cement, loosen the pigments (in colored grout) and thus result in discolored or mottled areas. ATTMCA (Association of Tile, Terrazzo, Marble Contractors and Affiliates, Inc., P.O. Box 13629, Jackson, MS 39236, Tel: (601) 939-2071) has published a bulletin entitled "Grouting and Cleaning Ceramic Floors With Latex Grout." This bulletin describes a precise method for cleaning tiles installed with Latex-Portland Cement Grout.
6. Proper curing of grout is essential for uniform, consistent results —not only for hardness and performance, but especially for accepted color. Unit heaters, open windows, air conditioning, etc. that result in uneven curing for the entire area will cause variation of shading. Damp curing by lightly spraying or fogging the surface with clean water (no puddles), followed by covering the surface with a single layer of 40 Lb. natural Kraft paper, (it breathes), will greatly enhance proper curing. Newspaper or polyethylene films are not recommended. The use of Latex- Portland Cement Grouts usually eliminates the necessity or requirement of damp-curing regular grouts for 72 hours. Consulting the Grout and Latex manufacturers for specific instruction is recommended.
7. The increased use of colored grouts has also increased the number of customer complaints concerning mottled or discolored cured joints. The results of many MMSA member laboratory and field testing programs has indicated the following potential causes:
7.1 Occasionally there may be a reaction between the alkaline water present in applied Portland Cement products, or the Portland Cement itself, prior to their final cure, with various alkaline soluble salts, such as lead, vanadium, selenium, iron or others used in the manufacturing process of glazed wall tile. Various colors or discoloration of grout may appear as a result of this reaction.
7.2 The migration of stains, which originate from the back mounting and/or glue used in some back mounted tile to the surface of the grout joint.
7.3 Materials used in the cleaning of tile work, both in preparation for grouting as well as after grouting, such as solvent type cleaners and general all purpose cleaners.
7.4 Chemical deposits on the grout surface brought about by mineral rich water migrating to the surface of the grout joint, evaporating, and leaving a thin layer of discoloration.
7.5 Chemical deposits brought about by certain organic mastic carriers, or from fresh mortar beds, migrating or dissipating through their normal curing process to the surface of the grout joint.
7.6 Poor cleaning habits, such as excessive water being used with sponges . . . many times the grout has started to take its initial set or firm up in the joints, and rubbing the tile and grout surface with a wet sponge practically destroys the grout surface. This is especially true for wide joints,1/8" or larger. Besides "cupping" the joint versus leaving it straight and level, this type of cleaning washes out the finely ground particles of Portland Cement along with the color pigments. The remaining sand is often not the color desired. For these reasons, a damp cheesecloth pad and terry cloth towel usually perform better than a damp or wet sponge. To determine the cause of grout discoloration, an unsatisfactory area should be studied by discussing the job conditions during the installation with the parties concerned. Next, scrape out some of the grout in question, noting the color on the surface, in the center, as well as that at the bottom of the joint. Normally, surface discoloration is caused by either grouting procedure or materials used to clean or maintain the completed installations. If the discoloration is the same all through the joint, top to bottom — the "cause" was probably mixed in during the preparation of the grout. If the discoloration is more dominant at the base of the joint, the "cause" is probably coming from behind or under the tile. The majority of the grout manufacturers uses every precaution available to provide non-staining and permanently colored grout. Discoloration usually comes from external sources.

Epoxy grouts make an excellent stain resistant and chemical resistant installation. But as with all grouting materials, care must be taken and the manufacturer’s directions must be followed. Care must be taken in handling epoxy grouts. Disposable gloves should be worn during the installation. Care must be taken to prevent epoxy grout from getting on the skin. Some people can get allergic skin reactions from exposure to epoxy grout. This can only occur through direct skin contact, not through the air.

One of the main problems with epoxy grout installations is removing the “haze” from the tile. Unlike cement grout, the haze is usually epoxy resin. If left on to long, the haze becomes very difficult to remove. The best time to remove the haze is during the preliminary cleaning of the installation. Most epoxy grout installations can withstand large amounts of water. Consult the manufacturer. A very wet terry cloth towel dragged across the tile and grout will remove the haze. If a sponge is used, use one pass of the sponge on each side and then clean the sponge. A secondary cleaning can be done after several hours if required. Haze left on the tile for longer periods of time may require epoxy grout removers.

Modified epoxy emulsion grouts frequently give similar performance as epoxy grouts with an installation technique closer to cement grouts. They normally do not cause allergic reactions. Modified emulsion grouts frequently do not have the same chemical resistance of a 100% epoxy grout. Follow the manufacturer’s directions for best results. As with 100% epoxy grouts, the main problem is haze left on the tile. Follow manufacturer’s instructions for best results.

Furan grouts are designed for high chemical resistance. Their installation requires special tools, techniques, and safety equipment. These type jobs are best left to furan grouting specialists.