What would the world look like if metal and concrete were not used in the construction of structures? The high-rising buildings that you see everywhere would not exist. However, between the two building materials, which is better?
Concrete is popular since it is versatile, durable, and easy to fabricate and mold into any shape. On the other hand, steel has gained traction in the market over the years due to its high adaptability, safety, and reliability. You can use either material or a combination of the two, depending on the needs of the project.
This article will help you understand more about working with both concrete and steel when constructing a building. You will clearly understand the pros and cons of using each product and choosing a material depending on the type of project.
Concrete: A Basic Overview
Concrete is one of the most common building materials used in the development of commercial buildings. It is created by mixing water and cement and solidifies and hardens due to hydration. The mixture solidifies and sets once mixed extensively along with other building components used in making the bond, including sand, cement, small stones, water, and gravel.
What Are Some of the Uses of Cement?
Cement is a manmade element that is used to make concrete. Once the cement is mixed with small stones, sand, gravel, and water, concrete is made. One of its best abilities is its malleability when freshly mixed and its ability to harden and become rock-like. This property explains why you can use concrete to build such things as pavements, foundations, motorways, overpasses, roads and bridges, and other architectural structures.
Types of Concrete
There are different types of concrete that can be used for building concrete structures. Some of the most popular types of concrete include:
Plain Cement Concrete
Plain cement concrete is created by mixing Portland cement with an aggregate and water in a set proportion. The most common mixing ratio is 1:2:4. When the mixture hardens, it becomes one homogenous mass.
Structures built with plain cement concrete develop a high compressive strength but lack tensile strength, unless reinforced with steel. You can use it to construct footpaths, pavements, concrete walls, and anywhere that is not subject to tensile strength.
Lightweight or cellular concrete is a type of concrete that flows with ease. The concrete self-levels itself with help from gravity. To get this type of concrete, lightweight aggregates such as clays, scoria, pumice, and expanded shales are used.
The materials have a low thermal conductivity of about 0.3 W/mK. Plain concrete develops a higher thermal conductivity that can range from 10-12 W/mK after mixing.
This type of concrete is often used on floor slabs, roofs, and window panels.
Precast concrete is cast and cured off-site, mainly in a factory within a controlled environment and with reusable molds. An added advantage of using precast concrete is the ability to manufacture it according to exact specifications.
The concrete is mainly used to construct structural components such as columns, floors, staircases, wall panels, tunnels, and beams.
Pre-stressed concrete units are popular in mega concrete projects. Here, the steel bars used inside the concrete are first stressed before applying the service load. The construction process requires placing the bars from the end of one unit to another.
Pre-stressed concrete combines both high-strength comprehensive properties of concrete and the high tensile strength of steel. It ensures that the lower section of the structure can absorb more tension. It is primarily used to construct floor beams, roofs, bridges, heavily loaded structures, and flyovers.
Reinforced concrete is one of the most common types of concrete used in modern construction. This type of concrete uses steel rods, wire mesh, and cables to increase its overall strength. Steel reinforcement is placed just before the concrete is poured. Otherwise known as rebar, this type of reinforcement increases both the concrete resistance to compressive forces and the steel resistance of tensile forces.
Reinforced concrete has an excellent thermal mass and is fire resistant. It can be used to make a wall, beam, foundation, or frame construction. Moreover, the buildings’ safety won’t be questionable, especially in fires or earthquakes.
Apart from the above, there are other types of concrete in the market that you can use depending on the type of construction you intend to build. They include:
- High-density concrete
- Glass-reinforced concrete
- Air-entrained concrete
- Self-compacting concrete
- Smart concrete
- Concrete fiber
- Polymer concrete
Pros of Using Concrete as a Construction Material
Concrete is one of the most widely used construction materials in the world. Its popularity is cemented by the numerous advantages that it brings to any structure. Here are some of the benefits of using concrete in a building project.
The production cost of cement concrete is very low compared to that of other construction materials. All the ingredients are simple and readily available. To create the concrete, you only need to mix water, cement, and aggregates, all of which you can readily find in the market.
Hardens at Room Temperature
Concrete will immediately start to harden at normal room temperature. Before long, the structure will have gained enough strength to support itself. You can, therefore, use concrete at any time regardless of the time or weather.
Easy to Mold and Shape
The final concrete mixture is in a viscous liquid state. It can, therefore, flow and adopt different shapes and sizes depending on your desired output. It is the best material to use to cast complex shapes in a structure.
Highly Energy Efficient
Only a small amount of energy is required to produce concrete when compared to steel. Only about 450 to 750 KWh/ ton are needed to produce plain cement concrete. The production of structural steel consumes almost 3 to 10 times more energy.
Has Excellent Water-Resistant Characteristics
Concrete can withstand water better than wood and steel. It can, however, suffer from corrosion if the water in use contains chemicals. However, it can withstand any wear and tear better than other construction materials. This property makes it ideal for construction in areas that require submerged structures.
For example, concrete is used to build dams, canals, pipelines, and waterfront structures. To prevent any instance of corrosion, water that contains chemicals such as chlorides and sulfates should be avoided.
Has a High-Temperature Resistance
Compared to other construction materials, concrete can withstand temperatures better. It contains a compound known as Calcium silicate hydrate, which can withstand temperatures of up to 910 degrees Celsius. The material is a poor conductor of heat. Therefore, it can only hold a small amount of heat for a given time.
It can withstand heat from a fire for 2 to 6 hours, giving firefighters enough time to perform a rescue operation in case of a fire outbreak.
Allows for Recycled Waste
Numerous industrial wastes can be recycled to normal aggregates and cement substitutes. As such, the use of concrete can help reduce the environmental impacts of industrial waste. Moreover, scraps help to improve the quality of a concrete structure.
Does Not Require Much Maintenance
Applying paint or a coating regularly on a concrete structure is not needed to protect it from weathering. The same can’t be said for wooden or steel structures. Since the coating only needs to be replaced when needed, maintenance fees are relatively low.
Cons of Using Concrete as a Construction Material
Has a Low Tensile Strength
While concrete may boast of high compression strength, it has a low tensile strength. The tensile strength is defined as the extent of the power needed to pull something to its breaking point. And because concrete is made up of many tiny stones, there are existing fissures on its body. For this reason, steel rebar and wire mesh are introduced to the concrete to help raise the tensile strength.
Has Low Toughness
Toughness is the ability of a material to withstand impact. When compared to steel, its ability to withstand toughness is incredibly low. Its toughness is only about 1-2 percent that of steel. In order to increase the amount of toughness in a structure, fiber reinforced concrete is often used.
Requires the Use of Formwork
When using concrete, the formwork can help mold different shapes depending on the structural needs. However, Formwork can be quite expensive to acquire and install. Moreover, the installation can consume a lot of time and labor. Precast and prefabrication techniques are one way to get around this issue.
Has a Long Curing Time
It may take a short time for concrete to start drying. However, for it to attain comprehensive strength, it may need to undergo curing 28-days after installation. This time can be reduced by using microwave curing, steam curing, and with the help of admixtures.
Steel: A Basic Overview
Steel has played an important role in construction ever since it was used in the first skyscrapers in the 19th century. Today, it takes a more significant role in the construction industry as more cities continue to raise more buildings to the sky. There is an increase in the demand for steel around the world by more than 50 percent due to an increase in the need for buildings and infrastructure.
The increase in steel popularity is due to its strength and durability. It does not warp, bend, twist, or buckle like wood or concrete. Instead, it is highly flexible and easy to install. It is sturdy enough to resist natural disasters such as earthquakes or hurricanes.
It is for this reason that steel dominates as a structural building material. You can find it in almost every building imaginable. Moreover, it can serve various purposes and work alongside other construction materials such as glass, concrete, and galvanized flat products.
Types of Steel for Construction
There are many different types of steel depending on the type and quantity, and type of alloy used. They also contain different physical and mechanical properties that are required for specific applications.
Below are the types of steel according to their chemical composition.
This is steel that consists of both iron and carbon. You can get different qualities of steel depending on the overall percentage of carbon. The higher the amount of carbon, the stronger and more brittle the steel.
It is easier to work with low carbon steel. For example, wrought iron steel can be used to make gates and decorative ironworks for stairs. Medium carbon steel can be used for structural steelwork. On the other hand, high carbon steel is very hard and may be non-malleable. It is, therefore, best for use in the manufacturing industry.
Alloy steel comes from the combination of carbon steel and one type of alloying element. The purpose of creating alloy steel is to improve the physical properties of the metal. For example, steel can be combined with manganese to make it harder and more robust. It’s also possible to combine it with aluminum to make its appearance more uniform.
Benefits of Using Steel as a Construction Material
There are several reasons why design consultants and builders choose steel as a construction material. Some of the benefits of using steel for construction are:
Strength and Design Freedom
Steel is a strong building material, and you can be assured of its durability. It also offers designers and builders more freedom in terms of shape, color, and texture. Due to its durability, strength, beauty, and malleability, steel gives architects the freedom to explore designs and provide fresh solutions. Steel has a long-spanning ability, and this gives rise to large open spaces without the need for load-bearing walls and intermediate columns.
Architects can create free-form combinations for facades and segmented curves because steel can bend to a certain radius. Steel is a factory-finished product that is often made to suit the desired specifications under a controlled environment. The final product is predictable, and this helps to eliminate any risk of onsite variability.
Can Be Assembled Fast and Efficiently
Steel is efficient and resourceful, and builders can assemble it fast and conveniently during all seasons. Steel requires minimal onsite labor since most components are pre-manufactured. Builders can erect a steel structure in several days. Depending on a project’s scale, using steel can reduce the construction time by 20-40%.
Steel reduces the amount of excavation required because it allows a minimal point of contact with the earth. Compared to other construction materials like concrete, structural steel frames are lighter and can be supported by a smaller and lighter foundation. Using steel for construction translates to greater efficiency and economic benefit. Steel enhances faster project completion.
A building’s function can change rapidly. For instance, a tenant may want to modify a building to create partitions or add more rooms. There may be a need to redemise the walls and alter a building’s layout to serve the occupants better. It is easy to alter steel-built structures into different designs.
With steel framing and floor systems, there is easy access or alterations to existing computer networking cables, electrical wiring, and communication systems. It is also easy to transform non-composite beams into a composite. Steel buildings offer high flexibility.
With steel construction, you can have more open spaces and fewer columns. Therefore, steel is a more cost-effective way of spanning extensive spaces. Builders can create extensive, column-free, internal spaces. In a single-story building, steel beams can help builders create large open spaces. In lattice or trussed construction, column-free design can be increased even further.
By minimizing the number of columns in a building, it becomes easier to customize or subdivide the internal spaces. Steel buildings have a higher potential for alteration and are more adaptable.
Even if the steel is not entirely fire-proof, it offers greater fire-resistance benefits compared to other construction materials. After extensive testing of how structural steel responds to fire exposure, there’s proof that steel offers fire resistance benefits that exceed those of most other construction materials. By using steel for construction, there is a reduction in the level of fire protection required.
After demolishing a steel building, its components can be reused or recycled. Recycling entails melting down the steel and repurposing it. Steel can be recycled countless times, yet it will not lose its unique properties. Currently, more than 30% of new steel is made from recycled materials. Therefore, steel helps save on the usage of natural resources.
Resilience During Earthquakes and Other Natural Disasters
Buildings constructed from steel are more likely to withstand natural disasters such as earthquakes and hurricanes. Earthquakes are hard to predict in terms of their frequency, magnitude, location, and duration. Therefore, when building a structure, it is important to ensure that it can withstand natural disasters. Steel is flexible and flexes under extreme pressure or loads instead of crumbling or crushing.
Beam-to-column connections in a steel building are designed to withstand gravity loads. However, these connections also have a considerable capacity to resist lateral loads resulting from earthquakes or strong winds. In the aftermath of an earthquake or hurricane, it is common to find steel buildings standing when all the other buildings are destroyed.
Less Impact on the Environment
Compared to concrete buildings, steel structures are lighter and have less of an impact on the environment since they require less-extensive foundations. Additionally, any steel that remains after construction can be compiled and recycled, meaning no waste materials remain at the construction site.
Steel Buildings Are Energy-Efficient
Compared to concrete buildings, steel is more energy efficient. Using steel for construction results in a cooler indoor environment in hot climates due to heat radiation from steel roofs and wall panels. In cold climate areas, double steel panel walls can work well because they are typically insulated and help preserve heat.
Disadvantages of Using Steel in Construction
Despite the many advantages of using steel for construction, steel also has some downsides. Some of the disadvantages of using steel in construction are:
Prone to Corrosion
Because steel is an alloy of iron, it is prone to corrosion. The corrosion of steel lessens the useful cross-section of structural components like columns, slabs, and beams. Additionally, in buildings where there is a steel-concrete bond, corrosion can have a significant impact. The steel reinforcement will start exhibiting an imperfect bond with the surrounding concrete, reducing the unit’s capacity. To solve this problem, builders can use an anti-corrosion application.
High Maintenance Costs
A steel structure might have high maintenance costs. When exposed to air and water, steel structures are prone to corrosion and often require periodic painting. Therefore, additional painting costs are likely over time. If not well-maintained, steel structures will lose their thickness over time. Steel structures may also lose weight of up to 35%, making them unable to withstand external loads.
Susceptible to Buckling
Steel structures are also susceptible to buckling. Steel consists of thin plates, and its overall member dimensions are smaller than its concrete counterparts. If the slender steel members are subjected to intense pressure, they are prone to buckling. Buckling is a sudden collapse due to compressive load. It might not be economical to use steel for columns because you have to use a considerable amount to prevent buckling.
May Not Be Readily Available in Certain Areas
In certain areas, steel may not be readily available. In places where steel is not available, the initial building costs for using steel might be much higher compared to other building materials. Higher initial costs have contributed to a decline in steel structures in many countries.
Steel structures are incombustible. However, in extreme temperatures, especially during fires, their strength is greatly compromised. Fire exposure could result in extensive deformations and deflections of the main members leading to a collapse. Therefore, when steel is used in construction, the costs of fireproofing the building can be high.
Both steel and concrete are popular building materials, and each has its pros and cons. Whether you use steel or concrete for construction will depend on several factors. The factors include your budget, your preference, and the availability of the building materials.
- World Steel Association: Reasons to use Steel in Residential Construction
- Northern Weldarc LTD: Advantages and disadvantages of structural steel structures
- Concrete Sask: Why Is Concrete Better?
- Designing Buildings Wiki: Concrete
- Rediscover Concrete: The benefits of concrete
- Civil Digital: 10 Advantages of Concrete as a Construction Material
- Civil Engineering: Advantages and Disadvantages of Concrete
- Wikipedia: Concrete
- Home Depot: Types of Concrete
- Wikipedia: Steel
- Weerg: Types of Steel