August 2018

Sun Damage to Concrete: What’s the Story?

by TRP Ready Mix on August 11, 2018

Slab of damaged, discoloured concrete

How to Protect and Repair Concrete Products from the Sun’s Harmful Effects

Can sunlight damage concrete?

It might surprise you to learn that, yes, UV rays can damage concrete over time and extended sun exposure, especially prolonged exposure in summer, can speed up this damage.

We know that ultraviolet (UV) radiation destroys both living and non-living structures—e.g. in the form of sunburns, skin prematurely ageing, and materials fading. But even strong, durable structures like concrete will deteriorate and weaken over time with exposure to UV radiation.

So whether you have an old or new concrete patio or driveway, protect your concrete from sun damage this summer to maintain its strength and extend its lifespan.

How Does Sunlight Damage Concrete?

The harmful UV radiation from sunlight can damage concrete in all its stages, from new, freshly-poured concrete to concrete that’s been around for a while.

Damage to Curing Concrete

Freshly poured concrete is susceptible to excessive damage from solar radiation. Direct sunlight causes water to evaporate from the concrete prematurely.

As a result, concrete will not have enough time (and water) to strengthen its structure before it dries out. And once it has dried out, it will experience shrinkage and cracking.

Damage to Cured Concrete

UV radiation breaks down the polymers and other bond chains of the concrete structure. Over time, this damage weakens the concrete, turns concrete into fine dust, and causes cracking and spalling away from joins or seams.

Pigments and colours on the surface of decorative concrete will break down as well, causing colour fading.

This concrete damage will only get worse with time and increased exposure to sunlight, resulting in a decreased life-span for your concrete.

How Can You Protect Your Concrete?

Protect your concrete from damage from the very start and throughout the years to extend the life of your concrete.

 While Curing

When curing freshly-poured concrete, you must take precautions to prevent water evaporation caused by direct sunlight.

For the duration of the curing process, which is typically 28 to 30 days, keep your concrete watered, covered, and sheltered from wind and sunlight.

Use a curing blanket, burlap, or a vinyl film to cover the concrete and keep it wet with a sprinkler or a hose.

You may also need to use sun-shades and wind-breaks to prevent both sunlight and wind from drying out the concrete.

 After Curing

As soon as your concrete has finished curing, use a concrete sealer to seal the concrete. Preferably, use a sealer with UV-blocking additives.

Concrete should be resealed every two years, or when the sealer shows signs of wear.

Along with sealing concrete, make sure to inspect for damage and repair concrete when needed before the damage worsens.

Do You Need to Use Concrete Sealer?

If you want to extend the life of your concrete, then, yes, you do need to use concrete sealer. Sealer protects concrete by acting as a barrier against damaging elements.

Along with blocking harmful UV rays, concrete sealer also protects against water, dirt, stains, colour fading, and scratches.

With this protective barrier, you can prevent concrete from cracking, spalling, staining, and losing strength.

There are various types of sealers available to suit your different concrete needs.

For decorative concrete, consider using an acrylic topical sealer to enhance the colour, add a gloss shine or create a matte finish, and protect the concrete from sunlight, rain, mould, and mildew.

If you want your concrete to have a non-slip surface, mix in an anti-skid material into the sealer. This is a convenient and safe option for pool decks, patios, and decorative concrete flooring.

Other types of sealers include penetrating sealers with silicates to strengthen concrete and create a waterproof barrier.

And sealers with epoxies, urethanes, and polyaspartics are often used in airports, industrial warehouses, and retail stores to protect concrete surfaces from high traffic and high chemical risks.

How Long Does It Take for Concrete Sealer to Dry?

The time it takes for concrete sealer to dry will depend on the type of sealer you use.

Penetrating sealers are usually dry and safe to walk and drive on after 24 hours. Topical sealers take up to 48 hours to dry and be safe for traffic.

What Happens to Dried Out Concrete?

Several types of damage occur with dried-out concrete. The most obvious damage is shrinkage, crumbling, and cracking on the surface, along with concrete developing a chalk-like texture.

Concrete also loses structural integrity when it dries out due to uneven curing throughout the structure. If the top part of a concrete slab dries out faster than the bottom, then the entire structure weakens and can develop cracks within as well as on top.

And when the top layer of concrete is dry, its edges tend to crumble while the entire surface can develop long cracks.

Whether you’re starting a new ready mixed concrete project, or your concrete is older, make sure to protect it from the sun’s harmful UV rays.

The bit of extra work to protect it while curing and with proper sealing is worth it to maintain strong, lasting concrete.