In the third century BC, the Romans produced the first concrete mix by blending water, volcanic ash, gravel, and gypsum or lime. After two millennia, concrete has earned its place as a dependable structural building element.
Steel, on the other hand, was not commonly employed in construction until the middle of the nineteenth century due to the difficulty of its production. In the 1850s, new techniques accelerated the manufacture of steel, and it swiftly rose to prominence as a strong and durable building material. Steel’s popularity continued to rise over the next 150 years, and it is currently, alongside concrete, one of the most extensively used structural materials.
Which of these materials is therefore better appropriate for your project?
There are various considerations to consider when deciding whether to employ concrete or steel as the primary building material for your project. Both are equally valuable as building materials. Concrete is more expensive but perhaps provides superior overall performance. To determine which material is ideal for your project, you must assess its strength, durability, fire resistance, sustainability, and affordability.
Strength
Compressive strength is the capacity of a substance to resist a crushing force. The compressive strength of slabs, beams, columns, and the foundation of a structure permits these elements to withstand the vertical loads of the structure without sustaining damage.
Tensile strength is the resistance of a material to rupture when stretched. Tensile strength is exemplified by a beam’s ability to resist vertical loads, which prevents its underside from elongating and splitting when a load is applied from above.
Shear failure is often produced by two misaligned forces operating in opposite directions on a structure, such as an earthquake or high winds. Shear strength is the capacity of a material to resist shear failure.
The compressive strength of concrete is exceptional, yet it is extremely fragile and breaks easily under tension. To counteract this weakness, tension-resistant bars are placed into the structure. Typically, these bars are made of steel; however, composite variants are also available.
The overall strength of reinforced concrete is derived from the compressive strength of the concrete and the tensile strength of the steel rebars. The shear strength is provided by the stirrups, which are shorter, perpendicular bars connected to the longitudinal bars of the structural member.
Steel’s tensile strength is one of its most desirable characteristics, but steel structures that are carefully built can match the overall strength of reinforced concrete structures. A steel structure’s compressive, tensile, and shear strength are dependent on its structural design.
Durability
Durability is the capacity of a material to withstand its environment. If their settings are optimized, both reinforced concrete and steel can endure for a very long time without degrading.
When properly adapted, reinforced concrete can withstand cycles of freezing and thawing, chemicals, seawater, moisture, solar radiation, and abrasion. Because concrete is inorganic, it is not susceptible to vermin attacks. Additionally, it does not burn or melt.
However, despite its excellent durability, reinforced concrete conceals a potential flaw: its corrosion-prone steel reinforcing. Rusting rebar loses its link with the surrounding concrete and produces iron oxide, which expands and causes tensile strains and eventual degradation. Although concrete’s natural alkalinity reduces rebar corrosion, reinforced concrete exposed to seawater or huge quantities of deicing salt may require further protection. Rebar that is epoxy-coated, stainless steel, or composite is suitable for this use.
As prone to corrosion as rebar, structural steel also requires protection. Paint, powder coating, sacrificial layers, and corrosion-inhibiting chemicals are all approaches for preventing or minimizing corrosion damage to structural steel.
Fire Resistance
The nature of reinforced concrete renders it essentially inert and therefore noncombustible, while its low rate of heat transmission limits the spread of fire between spaces.
However, both the concrete and the steel reinforcement might lose strength after prolonged exposure to high temperatures. At temperatures between 800°F and 1,200°F, concrete may begin to lose its compressive strength, depending on the aggregate type. According to studies, lightweight concrete has the highest fire resistance due to its insulating qualities and a lower rate of heat transmission.
Reinforced concrete is more resistant to fire than structural steel. It begins to lose strength at temperatures over 550°F and keeps only 50 percent of its yield strength at room temperature at 1,100°F. A variety of techniques can be used to reduce the rate of temperature rise in a building’s structural steel components. These may consist of fire-resistant coatings, barriers, cooling systems, concrete encasing, and active measures such as sprinklers.
Sustainability
When utilized in buildings, both concrete and steel are environmentally friendly. Approximately 85 percent of all steel used in the world is eventually recycled. Given the quantity of scrap metal and the simplicity of the recycling process, it makes perfect sense. In addition to minimizing the demand for newly mined resources, steel recycling uses just one-third as much energy as steel manufacturing.
Additionally, concrete has a number of sustainable properties. Most of it originates close to the construction site, reducing the amount of energy required for transport. After demolition, the debris can be repurposed into gravel, aggregate, or paving materials for road building, erosion control, landscaping, and the restoration of oceanic reefs, among other uses. Concrete that is not polluted can be used as aggregate in new mixtures.
Reusing concrete has numerous environmental advantages. It keeps debris out of landfills, reduces building waste, and substitutes gravel and stones that would otherwise be extracted and transported.
Cost
Reinforced concrete is typically more expensive than structural steel. The labor and materials required for erecting formwork and reinforcing bars, pouring concrete, and ensuring that it cures properly can account for a sizeable portion of total expenses.
Nevertheless, concrete costs are largely steady. Since 2000, the prices of various concrete products have continuously risen in tandem with the rate of inflation; this is a significant consideration when estimating the cost of future projects.
Insurance underwriters recognize concrete’s strength, durability, and fire resistance despite its greater price. Concrete constructions typically receive greater safety ratings and lower premiums from insurance companies.
Steel is less expensive and quicker to install than concrete but has a longer lead time. Due to its lower fire resistance, steel structures tend to have higher insurance premiums.
The price of steel has been famously unpredictable over the past two decades. They commenced a downward spiral with the Great Recession after reaching their high in the early months of 2008. Ten more years of ups and downs, and the price of steel increased again in 2018. Currently sliding in a buyer’s market, some analysts anticipate a recovery later in the year. Given the current state of global economic uncertainty, such price variations pose a significant budgetary burden that is likely to persist.
