"Concrete sealer" covers a lot of products that have very little in common. Some disappear into the slab. Some leave a shiny skin. Some aren't really sealers at all.
This is the reference page: what each type is, how it works, how it holds up to a Wisconsin winter, and how it gets applied. If you just want to know what to buy, skip ahead to the last section.
Two Families: Inside the Pores or On Top of the Surface
Penetrating sealers soak into the tiny pores and channels in concrete and react there. Silanes and siloxanes leave a water-repellent lining inside those pores. Densifiers react with the concrete itself to harden and tighten the surface. Either way, there's no film on top, so there's nothing to peel, scuff, or turn slippery. Water vapor can still escape from below.
Film-formers dry into a continuous layer on the surface, a lot like a clear coat on a car. They protect by covering the concrete, and they can deepen color and add gloss. The tradeoff is that the layer takes the wear. Tires, shovels, salt, and sun break it down, and moisture trapped under it can turn it cloudy.
Then there are coatings, like epoxy and polyurethane floor systems. They're film-formers taken much further: thicker, harder, and built for garage and interior floors rather than outdoor slabs.
The Big Comparison Table
| Type | How it works | Look | Grip when wet | Freeze-thaw and salt | Typical reapply | Best for |
|---|---|---|---|---|---|---|
| Silane | Smallest molecules, penetrates deepest, reacts in the pores to repel water | No visible change once dry | Unchanged | Strong. Cuts water and chloride absorption into the surface. | Several years; contractor estimates around 3–7, some makers claim longer | Driveways, aprons, salted walks and steps |
| Siloxane | Larger molecules that react in the pores to repel water, but don't reach as deep as silane | Natural matte; can darken slightly, especially if over-applied | Unchanged | Good water and salt repellency, shallower than silane | A few years; contractor estimates around 1–5 | Driveways, walks, patios, vertical masonry |
| Silicate densifier | Reacts with free lime in the concrete to form more of the binder that hardens it | Matte, minimal color change | Little change | Hardens and tightens the surface, but it isn't sold as a water repellent | 10+ years | Interior floors, dustproofing, polished concrete |
| Solvent-based acrylic | Dries to a clear film on top | High-gloss wet look, strong color boost, may yellow over time | Slippery when wet without anti-skid | Fair. The film wears fastest where salt and tires hit. | Every 1–3 years | Stamped, colored, and exposed aggregate patios |
| Water-based acrylic | Dries to a thinner, breathable film | Satin to gloss, moderate color boost | Can be slippery when wet; anti-skid recommended | Fair. Some are less stain resistant than solvent types. | Every 1–3 years | Decorative patios where low odor matters |
| Epoxy | Two-part resin that cures into a thick, hard layer | Thick, glossy, many colors | Slick when wet unless flake or grit is added | Not for outdoor slabs. Sunlight makes it chalk and discolor. | As a garage system, often 5–10 years depending on traffic | Garage and interior floors, usually under a topcoat |
| Polyurethane | Tough film, often used as a topcoat over epoxy | Matte to high gloss | Slick when wet unless grit is added | Aliphatic types resist sun better than epoxy, but it's still a film that needs grip added outdoors | As a garage system, often 5–10 years depending on traffic | Topcoat on garage floor systems |
Reapply ranges are typical figures from contractor-association estimates and product literature, not promises. Your label and a simple water test decide when it's actually time.
Penetrating Sealers, One at a Time
Silane
Silane molecules are the smallest of the group. That lets them get deeper into the concrete before they react and become water repellent. Many silane products are sold at 40% active content. Once a silane dries, you usually can't tell it's there. Some make water bead on the surface; others don't bead much at all and simply keep the water from soaking in, so the concrete doesn't turn dark when it gets wet. Several of the products on Wisconsin DOT's approved list of concrete protective surface treatments are silane-based.
Siloxane
Siloxanes are larger molecules, so they don't travel as deep as silanes. You'll often see lower active content on the label, around 10% on some products. They give a natural matte finish but can darken concrete a bit, especially when they're put on too heavily. Many products blend silane and siloxane together.
Silicate densifiers
Densifiers (sodium, potassium, or lithium silicates, plus colloidal silica) work differently. Curing concrete leaves behind free lime that adds no strength. A densifier reacts with that lime and forms more of the hard binder that holds concrete together, which tightens and hardens the surface. That's why they're used on warehouse floors and polished concrete. They're sold as hardeners and dustproofers, not water repellents. For keeping salt brine out of a driveway, silane or siloxane is the right tool.
Film-Formers and Coatings, One at a Time
Solvent-based acrylic
This is the classic wet-look sealer. It gives the strongest color boost and the most gloss, which is why it's popular on stamped and colored concrete. It builds a real film, can yellow with age, and has a strong odor and flammable fumes during application. Acrylics can also be softened by petroleum products, so gas and oil drips on a sealed driveway take a toll.
Water-based acrylic
Lower odor, a softer satin-to-gloss look, and a more breathable film. Some water-based versions are less stain resistant than solvent types. Like any acrylic, it wears fastest in traffic lanes.
Cure-and-seal
If your installer "sealed" your new concrete on pour day, this was probably it. Cure-and-seal products, typically acrylic, go on fresh concrete to hold moisture in while it cures. They offer short-term protection, not long-term winter protection, so plan on a real sealer once the slab is old enough.
Epoxy
Epoxy cures into a thick, hard, chemical-resistant layer, which makes it a strong base coat for garage floors. Sunlight is its weakness: epoxy chalks and discolors with UV exposure, so it doesn't belong on a driveway or front steps.
Polyurethane (and polyaspartic)
Polyurethane is usually the topcoat in a garage floor system, laid over an epoxy base. Aliphatic polyurethanes hold up to sunlight far better than epoxy. Polyaspartic is a related coating chemistry that's generally a professional-install product. These are coating systems rather than sealers, and they're part of our garage floor coating work.
How Sealers Get Applied
The method has to match the product. Here's how each one works and where it fits.
| Method | How it's done | Used for | Watch for |
|---|---|---|---|
| Low-pressure pump sprayer | Low pressure that lays down coarse droplets, not a fine mist | Penetrating sealers on driveways and walks; some water-based products | Wind drift onto cars, siding, and windows. Mist means the pressure is too high. |
| Low-pressure flood coat | Enough product that it stands on the surface briefly before soaking in, then puddles get broomed or rolled out | Penetrating sealers on porous, broom-finished concrete | Puddles left to sit. Some labels call for a second coat wet-on-wet, others after the first soaks in. |
| Roller | Thin, even coats with a nap roller, typically 3/8–1/2" for acrylics | Film-forming acrylics, smoother surfaces | Heavy coats that bubble, whiten, or leave roller marks |
| Back-rolling | A second person rolls right behind the sprayer to even out coverage and push product into texture. Anti-skid grit can be broadcast and rolled in to lock it into the film. | Textured and stamped concrete; any coat with anti-skid | Takes two people and steady pacing |
| Airless or HVLP sprayer | Faster coverage on big areas, using seals rated for the solvent | Large jobs, solvent-based products | Wrong seals fail with solvent products. Overspray travels. |
A few habits apply to every method: work in sections using the control joints as edges, keep a wet edge, and stay out of hot midday sun and wind.
Every type also needs the same starting conditions: clean, dry concrete, temperatures inside the label's window, and new concrete that's cured long enough. We cover timing for Green Bay weather in should you seal your concrete.
Picking One for Your Slab
This page explains what each sealer is. Choosing one comes down to your surface, the look you want, and what's on the concrete now. Our concrete sealer buying guide walks through that decision surface by surface.