Ask the Builder: Bringing stamped concrete back to life

If you’ve witnessed hundreds and hundreds of full moons in your lifetime and make frequent use of your critical-thinking skills, you know the sun is constantly at work ruining things inside and outside your home. One of these might be the expensive stamped-concrete patio, driveway or sidewalk you had installed a few years ago.

The same thing happens with exterior wood stains and sealers. I just concluded a fascinating test of a certain exterior wood stain, and it looks fantastic after two years of harsh exposure to the sun. I’m convinced that I may get another two years out of it, but eventually it will succumb to the sun’s ultraviolet rays.

You might wonder what is the exact mechanism that caused your stamped concrete, which you were probably told would look good for decades, to fade and look dull after as little as three to five years. A few years ago, while I was doing research for “Roofing Ripoff,” my expose of the shingle industry, I discovered that a small percentage of the sun’s UV rays contain active photons.

These photons are like miniature cruise missiles. When they strike fabrics, wood stains, paint, wood, certain soft metals and so forth, they can blast apart molecules and even break atomic bonds. Imagine photons being so strong that they can break the atomic bonds of copper, zinc and lead!

This is why the zinc coating on metal roofs disappears and why roof surfaces are free of algae and mold below copper and lead flashings. The atoms broken off by the UV rays wash down the roof with each rainfall and create a poisoned field where algae and mold can’t survive.

Knowing this, I believe you can now see why the solid pigments used by the stamped-concrete installers are child’s play for the UV rays striking your pavement. The photons simply destroy the pigments over time. But the problem is two-fold. The pigments are really not much different than a ganache icing on a birthday cake.

The color in your stamped concrete comes from pigments that have the consistency of cake flour for the most part. The concrete finisher broadcasts these dry pigments on top of the wet concrete and uses a wide float to get them to mix with the Portland cement paste that is coating the particles of sand and gravel in a thin top layer of the concrete.

This cement paste covering is extremely thin. While the cement paste can be sticky and bond well to the sand and gravel, it can be worn off with normal foot traffic and regular rainfall. Pressure washing a pigmented concrete slab is the kiss of death. Nothing ruins the appearance of stamped concrete faster than pressure washing its surface. I have photographs at askthebuilder.com comparing new and pressure-washed colored concrete paving bricks. The difference is like night and day.

When you remove this ultra-thin coating of colorized cement paste from the sand and gravel in the concrete, you begin to see the actual color of those components. What’s more, if you look closely at these stones, you’ll discover that they’re often quite smooth. Think how poorly a normal liquid stain adheres to a piece of glass – not well.

There are two methods that work to add color to concrete or previously stained stamped concrete. You can use reactive or nonreactive stains. The reactive acid stains contain metallic salts that can chemically react with the Portland cement paste and add color. The nonreactive stains are normally just films that try to adhere to the concrete, sand and gravel.

You simply need to manage your expectations when using either of these products, keeping in mind what the photons are going to do. They, as well as high-pressure, concentrated streams of water, will eventually cause the restoration stains to fade and not look so good. How long will it take? That’s the million-dollar question!

If you want your paving to hold a beautiful color for the truly long haul, you need to use traditional paving brick or natural stone. The color of the clay is solid throughout each brick. If you buy bricks that have a severe-weathering rating, they can withstand decades of Mother Nature’s abuse. Just travel to Athens, Ohio, and marvel at the paving brick still visible on a few downtown streets. It’s unchanged since it was installed well over 100 years ago.

As for stone, the color range might not be as wide as with paving brick, but it stands up to the elements like nothing else. Granite is a great example. Think of how the color of granite never changes over time. You know this to be true if you visit cemeteries on a regular basis and note the granite headstones.

Granite cobblestones may be available to you in a wide variety of different muted colors. There’s a stunning red granite bedrock on Mt. Desert Island, Maine, but that quarry has long since ceased operation. White or light-gray granite is usually the cobblestone I see in stock at most stone supply businesses.

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