Safety & Regulations | Design & Engineering
Designing for Thermal Protection - Think Twice About Concrete
We know that steel is a superior building material when it comes to safety, cost, time, design possibilities, and environmental considerations. Because it has the highest strength-to-weight ratio, we know steel can stand up to just about anything. Furthermore, because steel is a metal, you might be wondering about how it fares when it comes to thermal protection from extreme heat.
We’re going to tell you exactly why steel is the best material for thermal protection - and why concrete comes up short.
The Hazards of Concrete
Traditional thinking might suggest that because reinforced concrete is inert and incombustible, it might be the best choice when dealing with thermal energy. But while concrete is fire-resistant, it’s also brittle and lacks tensile strength. That means it’s more likely to break than bend under stress. And that makes concrete a safety hazard since fragments from fractures can strike anyone around the structure. The last thing you want is to jeopardize the people on site.
However, concrete has a low rate of heat transfer, which can help prevent the spread of fire. It also has good compressive strength. But concrete’s poor elasticity and its weakness when handling shear stress mean it simply can’t perform under pressure like steel can.
We’ve long known about the potential for concrete to explode when it’s heated to high enough temperatures. Heat causes concrete to dry out, and the water vapor trapped inside has fewer places to go. This causes thermal expansion (and later, contraction). As a result, concrete becomes stressed and begins to crack.
It tells us a lot that engineers attempt to make concrete structures safer by embedding steel bars to prevent dislocation and other structural damage.
The Benefits of Steel
Steel is durable and strong, and because it’s an excellent conductor of thermal energy, it can stand up to the heat in ways that concrete cannot. For example, when steel comes into contact with extreme heat, its electrons can absorb that heat and freely carry the thermal energy away from the source quickly, increasing steel’s resistance to fire.
Steel can also hold up to the heat generated by explosions. During a blast, energy is released as thermal radiation. Because of steel’s strength, conductivity, and ductility, it can not only survive extreme temperatures but resist both the shock and ground waves that come after. We’ve seen in the past that buildings subject to otherwise catastrophic explosions have still had their steel elements survive the blasts.
While steel is non-combustible, its strength can eventually be compromised under extreme temperatures, just like any other material. However, the addition of intumescent coatings can further enhance steel’s safety. These coatings are now standard for most structures and can expand when heated, forming a further protective blanket around steel.
Coatings can upgrade the fire rating of a steel structure by up to four hours, meaning there’s far more time for first responders to work the scene safely. Of course, because steel blast resistant buildings can be modified easily to include active cooling measures such as sprinklers, fire protection systems may solve problems before they get out of hand.
People are the most important resource we have, so it’s important to know that when a fire cannot be controlled quickly, steel blast resistant buildings give you more time to move people to safety. That’s why they’re recognized as non-combustible by the International Building Code (IBC).
The Importance of Testing to Guarantee Thermal Protection
When a structure’s integrity is at stake, you want proof that your blast-resistant building can truly take the heat. That’s why you should only invest in products that have gone through extensive testing.
The most ethical way to settle on a building material is to review the proof that it can withstand a blast.
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