Q: We are about to work on a job that involves sealing a concrete floor. I’ve read that manufacturers have lowered the VOC content in paints and coatings and are considering switching to water-based concrete sealers. What are the pros and cons of each and what should I expect?

A: Lowering volatile organic compound (VOC) content has been a popular topic lately, largely due to increasingly restrictive regulations across the country requiring lower VOC levels in various paint and coatings applications.

  • Although different, water- and solvent-based sealers both result in a sealed concrete surface.

    Credit: Dow Construction Chemicals

    Although different, water- and solvent-based sealers both result in a sealed concrete surface.
Because of the more restrictive regulatory environment, knowing the characteristics of the different types of sealers, which can vary from very high VOC (more than 400 grams per liter) to very low VOC (less than 100 grams per liter), can help you to determine which one is right for your project.

Concrete sealers come in both water-based varieties (typically lower VOC) and solvent-based types (normally high VOC). Both water- and solvent-based sealers act as decorative and protective topcoats for concrete and are applied after concrete curing is complete. They are designed to protect the concrete from wear and tear and are the primary means of providing chemical and stain resistance for concrete. These sealers add to aesthetics, including gloss and long-term color enhancement.

The most UV-resistant sealers are based on 100% acrylic polymers. Advances in technology now present contractors with a choice of high-quality acrylic sealer options, using either water-based polymer emulsions or solvent-based polymer solutions. Both types of sealers act similarly to produce the continuous coating that seals the concrete, as the diagram below shows.

In the case of a water-based sealer, the polymer particles are dispersed in water. When the sealer is applied to concrete, the water evaporates and the polymer particles move closer together. As the evaporation of water continues, the polymer particles begin to deform and fuse together, eventually forming a continuous clear coating.

With a solvent-based sealer, polymers are not present as separate particles. Instead, the polymer and solvent form a continuous, clear polymer solution. When solvent evaporates from a solvent-based sealer, the polymer chains are drawn closer together and eventually entangle. For both water- and solvent-based sealers, the polymer remains on the concrete surface. This is why a sealed concrete surface often appears glossy.

If you are considering a switch to water-based sealers for some or all of your projects, it is helpful to note that once applied and cured, water- and solvent-based sealers function in a similar fashion. Some of the attributes common to both water- and solvent-based sealers include:

Tough and durable. The most important similarity between the two types of sealers is they both work to protect the concrete. This can last for two to three years with the best performing acrylic sealers exposed outdoors. Both types also will provide stain protection, so various spilled food, chemicals, and automotive stains typically can be removed before permanent staining occurs.

Easy to apply. Both water- and solvent-based sealers typically are available in fully formulated, ready-to-apply variations. They can be either sprayed or rolled on, depending on the project.

UV resistance. Because 100% acrylic sealers are fully transparent to UV light, they will not undergo the photochemical breakdown experienced by more UV-absorbent polymers, such as styrene-acrylics, nonaliphatic polyurethanes, and most epoxies. The UV resistance provided by 100% acrylic-based concrete sealers can lead to extended service and protection.

Although there are similarities between water- and solvent-based sealers, differences between the two do exist, such as:

Appearance. One key difference between water-based and solvent-based sealers is their appearance after application and cure. Solvent-based sealers tend to wet-out and penetrate concrete surfaces very well. This results in a glossier finish that enhances the color of the underlying concrete. Water-based sealers appear milky white as they are applied because the polymer particles in the sealer scatter visible light differently than the water in which they are dispersed. After curing, water-based sealers tend to provide a lower-gloss, matte finish.

Handling. Some of the more attractive benefits of water-based sealers is that they are nonflammable, have no strong solvent odor, and allow for quick and easy clean-up once the application is complete. For a busy contractor, this time savings could mean the difference between arriving on time, or arriving late to the next job.

The finished performance properties of water-based and solvent-based sealers are fairly similar, and provide a long lasting and high level of protection to newly finished or aged concrete surfaces. Water-based sealers are a good choice when you are looking for a low-VOC, high-performance concrete sealer that is durable and easy to work with, but without the odor and cleanup issues associated with solvent-based sealers.

Contributed by Dow Construction Chemicals. Visit www.dowconstructionchemicals.com for more information.