The Processes of Building A Datacenter
The demand for datacenters is on the rise. If you’re a mid-to-large enterprise and don’t already have your own datacenter, [...]
Steel and concrete go head to head as two of the most popular building materials for commercial structures.
Whether you’re building a standalone shop, a 250,000 sq. ft. warehouse, or a neighborhood rec center, concrete and steel are both viable options.
But is one stronger than the other?
Will steel withstand hurricanes, fires, or the test of time better than concrete?
Below, we’ll compare concrete and steel to determine which is best.
Table of Contents
1. Compressive and Tensile Strength
2. Weight vs. Strength
3. Fire Resistance
4. In Cold and Hot Climates
5. Corrosion and Water
6. Longevity
7. Other Factors Worth Considering
When we say “strength,” we mean two things:
Compressive strength and tensile strength.
Compressive strength describes how much pressure a material can bear without crushing (or compression).
Tensile strength is the opposite — how well a material withstands pulling (or tension).
Let’s compare each of these strengths for both steel and concrete.
Modern steel buildings are typically made from mild steel. This low-carbon steel is known for its ductility (resistance to deformation) and can be carburized under high heat to strengthen its outer layer.
The “how” matters, too.
When we erect prefabricated buildings, everything from the wall panels to the girts to the fasteners are made of mild steel. As a result, every connection within the structure is just as strong as the next.
But “mild” does not mean “weak.”
In fact, the tensile strength of steel is typically 58,000+ PSI, while its compressive strength is a much lower 36,000+ PSI.
Based on strength alone, steel is more resilient to outside forces. Its strength, combined with its flexible fasteners that “give” with force, allow for subtle swaying during extreme weather events while preventing total collapse.
Typical concrete is less than one-tenth as strong as structural steel. The compressive strength of concrete is a substantially lower 4,000+ PSI with a 725+ PSI tensile strength.
We can blame its low tensile strength on how concrete is made — by mixing cement, water, and aggregate (or stones). While bound together, these stones are easy to pull apart under heavy force, increasing the odds of cracking.
However, reinforced concrete substantially levels the playing field with the help of — you guessed it — steel. Steel rebar is essentially a grid of interconnected steel rods that mixed concrete is then poured over.
The normally brittle concrete achieves a much higher tensile strength and flexibility, making it more resilient to cracking and breakage.
Without getting too technical, a strength-to-weight ratio — also called “specific strength” — reveals how strong a material is in relation to its density.
A higher STW indicates that the material is either unbelievably strong or relatively strong despite being lightweight.
Both steel and concrete are strong, but which has a higher STW?
Steel weighs in at about 490 pounds per cubic foot. But thanks to its high compressive and tensile strength, low-carbon steel has an impressive strength-to-weight ratio of 46.4 N⋅m/kg.
Not only is that nearly nine times the STW of concrete, but it also explains the resilience of steel despite its thin panels and gap-filled framework.
Concrete is much lighter than steel at about 150 pounds per cubic foot. Yet, its lower strength values decrease its specific strength to just 5.22 N⋅m/kg.
Thus, steel becomes a much better choice for buildings that need to be lightweight without sacrificing durability and strength.
Nobody ever plans for their commercial building to go up in flames.
But if it does happen to your building, how will the blaze impact your structure?
Here’s a closer look at the fire protection provided by steel and concrete.
The American Institute of Steel Construction (AISC) considers structural steel to be fire-resistant and non-combustible.
Steel doesn’t burn or ignite like typical timber. So in the rare chance a fire engulfs the structure, the steel members could soften to half their strength and risk collapse once temperatures reach ~600 degrees Fahrenheit.
The steel won’t necessarily burn, but it may bend, flex, or melt when exposed to extremely high temperatures.
By “fire-resistant,” we mean that steel won’t feed an ongoing fire. The flames may spread from equipment to furniture and vice versa, but the steel won’t ignite and spread any flames.
Concrete is also naturally fire-resistant and non-combustible, making it an equally smart — or even slightly better — choice for fire prevention.
For buildings with separate offices or nooks, interior concrete walls create a fire-resistant shell around each individual area.
This resists the spread of flames from room to room (for walls) and floor to floor (for slabs). But concrete also has a reputation for surviving extreme heat for up to four hours without risking severe structural integrity.
Concrete doesn’t burn for the same reason as steel — nothing within the material is flammable or fuels fire.
Some construction materials fare better in certain climates, while others are versatile enough to tolerate the Northeast’s chill and the Midwest’s heat.
Does climate matter when you’re building with steel and concrete?
The primary concern with metals like steel is they expand in the heat and shrink in the cold.
For steel structures, where each element is connected with a fastener, extreme weather changes could damage these links. Cold air could pull panels and steel framing elements apart, while heat could force an overlap.
However, like concrete structures, steel buildings have built-in expansion joints that allow them to shrink and expand without damaging the building.
Compared to steel, concrete construction is less tolerant of extreme temperature changes.
Unexpected temperature dips and increases could cause extensive thermal shock, cracking, and spalling (or peeling) of the outer layer. Freeze-thaw cycles can do the same.
But the concrete-temperature trouble begins early in the process, even before a crane tilts up the precast walls.
Research shows that concrete cures best at around 55 degrees Fahrenheit, reaching a strength of 110% a year after pouring. Compare that to 73 degrees (100%), 90 degrees (90%), 105 degrees (92%), and 120 degrees (73%).
The next “element” of concern is water exposure. How will the building hold up in a structural strength sense when it rains, snows, or floods?
Let’s find out.
Unfortunately, steel buildings will develop rust the longer they’re exposed to airborne chemicals, acidic rain, and moisture (combined with oxygen).
Corroded exterior steel could cause roof leaks, mold (when insulation absorbs leaking water), and weak elements that put the structure’s integrity at risk.
Luckily, there are two ways to prevent this strength-defeating corrosion.
The first is that structural steel is often coated with a moisture-proof barrier made of molten zinc. Next is red iron steel, which is even more effective with an exterior iron-oxide coating that wicks away moisture to resist rust.
Galvalume roof panels and rust-proof fasteners can further prevent corrosion.
We assume that steel rusts because it’s an alloy, but concrete structures corrode, too. The natural acids found in rainwater and saltwater can strip away concrete’s outer layer and weaken the structure.
The biggest corrosion concern isn’t the concrete itself, but rather the steel bars embedded within it. Rebar exposed to the elements through cracks or leaks can corrode, forcing the concrete to expand and crack.
With a proper barrier to prevent salt and acid rain exposure, rebar shouldn’t corrode or impact the concrete’s structural integrity. This fact alone makes concrete better than steel in wetter environments.
Does steel or concrete last longer with all of these strength factors combined?
We’ll answer that question below.
Many predict that the average steel building construction will last 50 to 100 years. But the first steel-framed building dates back to 1885 (in Chicago).
So, it’s still unclear how much recent technology impacts steel’s life expectancy.
Reputable steel building manufacturers also back their structures with a litany of warranties to guarantee an even longer lifespan.
A workmanship warranty could expire after a single year. But elements like roof sheeting, trusses, and fasteners could come with a 20-year warranty — or even a lifetime!
Not only does this speak to the quality of these buildings, but it also opens the door to regular repairs that can maintain strength for years to come.
Structural concrete with reinforcing bars has a similar 50–100-year estimated lifespan. However, concrete structures may last even longer with waterproofing, limited exposure to acid and salt, and proper curing.
In fact, one of the first all-concrete homes — built in New York in 1875 — still stands today nearly 150 years later.
Beyond strength, these factors will determine whether steel or concrete is best for your next commercial building project:
If you need a customized commercial building, are you better off with a steel or concrete structure?
Steel is one of the more flexible materials. Pre-engineered steel buildings can be customized to your exact needs, including width, height, insulation type, shape, and more.
Concrete is also remarkably versatile, but more in its wide range of purposes. With the help of molding, hardened concrete can become a custom-designed floor slab, tilt-up wall, roof, sidewalk, and more.
Which of these two materials is more cost-effective?
Steel is generally more affordable than concrete, requiring less material and labor. Not surprisingly, the greater strength and corrosion-resistance of stainless steel or other types of steel make it more expensive than carbon.
Concrete carries a heavier price tag. Not only does it cost more per ton, but concrete buildings take longer to erect and require expensive machinery like cranes.
How does building a steel or concrete structure impact the planet’s limited natural resources?
At the end of their natural lifespan, steel buildings become 100% recycled material. Steel can be melted down at a steel plant and later reused to build again, making it one of earth’s “greenest” materials.
Concrete can be reused after demolition as gravel or even new concrete. However, the concrete industry creates up to 8% of the world’s carbon dioxide (CO2) during cement production.
What’s the average construction time for steel and concrete buildings?
Steel’s lead time tends to be longer than concrete, as cutting custom steel elements requires pre-planning and precision. Otherwise, erecting a steel structure could take a matter of weeks.
Concrete’s building process is somewhat longer than steel, though we can blame that mostly on the curing process. It typically takes about four days for each concrete panel to be cured enough to tilt up into place.
Does it matter whether you’re building a small shop, 100-story skyscraper, storage facility, or office building?
Structural steel tends to be better for larger and heavier structures, like skyscrapers and commercial buildings. These large-scale structures have the benefit of size while still being able to support the structure above it.
Concrete is best for warehouses, smaller commercial buildings, and residential applications. Its substantially lower tensile and compressive strength raises concerns about its practicality for high-rise buildings.
All factors considered, steel is stronger and just generally a better option than concrete in most scenarios.
Topping the list of reasons is steel’s ability to withstand higher tensile loads and compressive loads than reinforced concrete.
But that’s only scraping the surface.
Steel is also highly effective against fire, water, and extreme weather. Not to mention, it lasts just as long as concrete with those extra benefits!
If you’re torn between steel and concrete, steel works best.
And if you’re looking for a commercial contractor to help you design and construct your building, contact FMP Construction today.
Learn about our services here:
Pre-Construction | General Contracting | Architecture and Engineering | Pre-Engineered Steel Buildings
