The final stage of the concrete polishing process is using a sealer to protect the floor from stains. Sealing a floor brings out the beauty of the concrete, enriching and enhancing the colour. The choice of sealer affects not just the appearance, but the performance of the concrete. Sealing a floor helps protect against liquids absorbing into the floor, as well as dirt and grease. Selecting the right sealer will provide the strongest possible protection. The three most commonly used types of floor sealer are penetrating, semi-penetrating and topical. Each has its own advantages and disadvantages. What is suitable for a warehouse may be unsuitable for a living space. Kitchens, bathrooms and exterior concrete all have specialist requirements that need to be taken into consideration.
Keeping a floor at its best requires regular maintenance. A pH neutral cleaner and a floor scrubber will normally achieve this. Even with maintenance, sealers will sometimes need to be re-applied. How regularly this is the case depends on the type of sealer and the amount of use the floor sees. Before committing to a particular product or brand of sealer the long terms needs of the building should be considered. If a floor has to have sealer reapplied the whole building may have to be closed off while the work is carried out. Proper planning and regular maintenance help to eliminate this risk.
Penetrating Concrete Sealers
Penetrating sealers are the best solution for large floors which will see a lot of mechanical or foot traffic, as they will not wear down. They provide a more natural finish, which is key to creating a rustic or industrial style concrete floor. Most penetrating sealers are breathable and will allow moisture to escape the floor. This makes them the most suitable type of sealer for exterior concrete.
Penetrating sealers work by creating a chemical barrier in the concrete. They penetrate the surface and react inside the capillaries of the floor, shielding against moisture and chemicals. They do not add a high degree of extra sheen or gloss to the floor and have a much smaller impact on the appearance of the concrete than other types of sealer. Because the sealer penetrates the floor rather than sitting on top of it, it is not susceptible to being worn away like a topical sealer. Over time, however, it will break down and further applications will be required.
A penetrating sealer will not provide an absolute barrier. Moisture and dirt will be held at surface level, but it is important to clean them away before too long. Leaving any liquid on the surface for a long period of time will result in it absorbing into the floor. They are applied using a pump sprayer and a fibre mop. Drying time will vary with product and temperature. Pools should not be allowed to form, and any excess penetrating sealer should be removed with a concrete burnishing machine. Once fully dried, a second coat can be applied to provide extra protection.
Acrylic Concrete Sealers
Otherwise known as guard sealers, an acrylic sealer has two elements. A topical aspect increases the gloss look of the floor. They also provide stain resistance and repel liquids. These elements work in tandem to protect the concrete. They are more susceptible to wear than other topical types of concrete sealer and they will break down under heavy foot traffic. For this reason they are rarely used in commercial or industrial buildings. They are suitable for use on both internal and external concrete floors. Acrylic sealers are available as either solvent or water based. Solvent based acrylic sealers offer deeper colour enhancement and perform better on exterior concrete.
Most acrylic sealers do not advise using high speed burnishing pads to maintain their surface, as this can quickly wear away the topical aspect. They can be applied in the same way as a penetrating sealer but adding more than one coat will result in diminishing returns. Due to their low cost they are most often used on projects where economy is a key issue, such as enhancing stamped concrete driveways. Another major advantage is that they dry rapidly often being touch-dry within an hour.
Topical Concrete Sealers
A topical sealer bonds to the surface of the concrete, creating a film layer of protection against dirt and liquids. Topical sealers are either polyurethane or epoxy based. Polyurethane topical sealers create a thick layer of protection on the floor. They are available in both solvent and water based. The finish is transparent and will not yellow under UV. Polyurethane sealers are hydrophobic, so they will not allow moisture to escape the floor. This means that floor must have fully hydrated before application. No moisture should be present on the surface of the floor either. The resulting floor will be highly protected against liquids, chemicals and abrasions.
Epoxy based sealers are normally a two-component mix. This means they need to be prepared with care and then applied using a roller. Transparent and tinted epoxy sealers are available. Like polyurethane, epoxy based sealers are hydrophobic and will prevent liquids from penetrating the floor. This also means that they are not breathable and will trap moisture in the floor. Epoxy sealers create a long-lasting, hard wearing floor, deepening the natural colour of the concrete and adding a glossy finish. Epoxy finishes can yellow over time in the presence of UV light.
While topical sealers are abrasion resistant, they will accrue damage over time. Regular maintenance is vital to prevent stains and scuffs from impacting the floor’s appearance. On high traffic floors, such as commercial, retail or hospitality locations, topical sealers will wear down over time. This will require re-application.
How much maintenance a floor will require changes based on the type of concrete sealer which is used. Floors which have a penetrating sealer applied are at the greatest risk of liquid absorption and staining. Spills need to be cleaned up promptly to avoid this. To maintain the concrete, diamond impregnated burnishing pads can be used with an auto scrubber and a pH neutral cleaning agent. Faster burnishing machine can be used to re-hone the floor and renew the finish, or to prepare it for a re-application of sealer. Topical sealers should be maintained according to individual product guidelines. Using burnishing pads on topical or semi-penetrating sealers can wear them away.
Q. Does concrete need to be sealed?
A. If a concrete floor is not sealed, it is more susceptible to damage from liquids, oils and dirt. This can discolour and damage the concrete. It also increases the risk of freeze/thaw damage in exterior concrete.
Q. What does concrete look like once it is sealed?
A. The final look will depend on the choice of product. Penetrating sealers will deepen the colours in the floor but will provide little in the way of extra gloss or shine. Topical sealers provide a more significant colour deepening effect and create a gloss look. How intense this is will depend on the specific product.
Q. Does sealer make concrete slippery?
A. Penetrating sealer will not have much effect on the grip rating of the concrete. Topical coating can increase slip. Some topical sealers have complimentary products which can be added to increase grip.
Q. What is the best method of applying sealer?
A. Penetrating and semi-penetrating sealers are generally applied with a pump spray and a fibre mop. Topical coatings are normally applied using a notched squeegee or a roller.
Q. What does sealer protect against?
A. While water and dirt will be repelled by all sealers, oil and grease are harder to defend against. Topical sealers will also protect against oil and grease.
Q. Can other chemicals damage sealers?
A. Acrylic sealers can be weakened by petroleum distillates, while penetrating sealers can be weakened by acidic chemicals. Topical sealers are more resistant to chemical damages but can chip and wear away.
Q. How long will a sealer last?
A. Under average conditions a penetrating sealer will last 10+ years. Topical sealers will last between 5- 10 years. Acrylic semi-penetrating sealers will last 3-5 years, depending on conditions.