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Decorative Concrete Sealers

Coating sealers provide better protection of the substrate and are easier to clean than penetrating sealers. However, they create a smoother surface that is more likely to present a slip hazard under wet conditions. The incorporation of aggregate particles in the coating material can help alleviate this potential liability, but requires a careful understanding of the correct size and amount of the aggregate relative to the sealer type selected for the project.

Most penetrating sealers are made from by-products of silicone called silanes, siloxanes, or siliconates, and are designed to penetrate concrete pores. Once applied, they react with the alkaline materials in the concrete mix and the moisture present to form a silicone seal, making concrete water-repellent. Penetrating sealers usually cost more, but generally last longer before repair or reapplication is required. Another reason penetrating sealers are popular is, that when properly applied, they do not change the concrete's appearance.

Coating sealers are usually made from epoxy, acrylic or urethane-based compounds. They form a thin coating on the concrete's surface, leaving a wet look similar to varnish on wood. These products tend to be less expensive per gallon than penetrating sealers, but need re-applications more frequently. They also protect against some stains better. However, some coating sealers tend to darken concrete. In addition, they normally require the addition of aggregates to increase surface friction and help keep feet or tires from slipping on the finished surface.

Other important considerations and properties to evaluate when selecting a sealer include penetration depth, reactivity to concrete materials, service life, water absorption, water vapor transmission, and crack bridging characteristics. Moreover, sealers can have (or not have) other features that may be important to the project, including UV protection, matte, satin or high gloss finishes, coloring agents, chemical-resistance. Newer cross-linked multi-component sealers offer improved durability and adhesion. A review of the appropriate project requirements should be part of the selection process for each project.

Important Selection Factors
The single most important factor in selecting an appropriate sealer is defining the impact the environment will have on the particular surface to be sealed. Before specifying the sealer, you should carry out a thorough site inspection with the customer to assess such factors as anticipated type and severity of conditions (e.g., pedestrian, vehicular, machinery, chemicals, etc.), the condition of the substrate and installation environment. Will the surface be exposed to sunlight or artificial UV sources (e.g., metal halide lighting)? Are there unusual humidity issues to be considered?

The timing/scheduling of the installation may also have an impact on the sealers available for selection. Some sealers allow for quick installation, and therefore keep downtime costs to a minimum, while others require cure times of one week to achieve full chemical and mechanical resistance. As a rule, water-based, solvent free materials allow for simpler application from a health and safety perspective.

Another factor is the cost of the application. Cost considerations extend beyond the final bill presented to the owner by the contractor. Pre-project cost analysis should include the impact of the overall installation time, the life expectancy of the sealer, and how much additional materials and work will be necessary for ongoing maintenance. These are all factors associated with the total cost of any sealer application.

It is not necessarily more cost-effective to choose the cheapest sealer, when a longer life cycle option, although appearing more expensive at the initial pricing phase, will be more cost effective for the owner in the long-term than a finish that needs extensive repairs and recoating year after year.

Similarly, for high-solid coating sealers (epoxy, urethane and polyurethane) pricing analysis should be based on mil-thickness requirements for the installation, which can vary manufacturer to manufacturer for the same "recommended" square footage coverage per gallon of sealer. One other important factor related to calculating the actual cost of multi-component mixes is that the result of the combined solutions may be less than equal to the "gallon" stated in the coverage specification due to allowances for mixing.