Concrete is popular for many reasons (i.e., on roads, driveways, planters, sidewalks, and paving blocks). Yet, the process is much more elaborate when used in construction.
Should concrete be your material of choice for your upcoming project?
How is structural concrete used in the building process, and what types are available?
We’ll answer these questions and more in this general guide to structural concrete:
What Is Structural Concrete?
Structural concrete is a type of concrete used in the building process as part of the structure or used to carry part of the structure’s load.
How Structural Concrete Is Used in the Construction Process
Very few components in a construction project can’t use concrete. Depending on the design methods, a project can implement structural concrete from the foundations to the roof.
Components of a Structural Concrete Building
Here’s a list of the components that we can construct out of concrete:
These include concrete forms under the soil’s surface, such as the basement or foundation.
The superstructure is the above-ground structure. This group includes the main building and roof.
Concrete slabs are most common when constructing a concrete floor or roofing.
Beams are long reinforcements under the slabs that transfer the loads to the existing concrete columns below.
Columns are vertical beams that help keep the slabs from dipping due to the above load.
These can be exterior or interior walls, usually consisting of vertical slabs or poured concrete into formwork.
Footings are pads or beams directly on top of the soil at the job site that provide a solid base to place the rest of the structural concrete.
What’s really behind the concrete construction craze? Read Why Are Concrete Walls so Popular in Commercial Construction? to find out!
Steps in Structural Concrete Construction
There are some critical steps a crew must follow to create a concrete structure, including:
1. Site Preparation
The first step is to prepare the site for construction. The soil needs to be level and compact to hold the concrete with as little shifting as possible.
A layer of gravel may be necessary to cover the soil after compaction. Depending on the soil type at the site, another ingredient may also be necessary.
2. Formwork Built
After the site is ready for construction, a crew will build stationary or removable formwork according to design. This process happens in layers from the ground up.
Formwork is one of the most costly, labor, and time-intensive steps of concrete construction.
3. Reinforcements Placed
Rebar or steel mesh add strength to the concrete.
4. Concrete Mixed and Poured
Before the crew can pour the concrete into the formwork, it requires mixing. The concrete mix needs the correct water-to-concrete ratio for a solid final product.
Admixtures may also be necessary to add to the mix.
The crew then pours the concrete into the formwork and applies vibrations to remove air pockets.
5. Concrete Cured
After the forms are full of concrete, the concrete must harden and cure. Concrete can harden enough to remove the formwork in a matter of days, but it must then be cured.
The accepted number of days for curing is 28 days, but many factors can affect the drying and curing process.
Structural Concrete Must Support Specific Loads
A structurally sound concrete building will be engineered to support the loads placed upon it.
There are three types of loads to take into consideration:
The dead load is the weight of the concrete structure and any material placed on it.
Live loads include occupancy loads or traffic loads. In most cases, this is the weight of the people and items in the building.
Weather can also be a load. Wind, earthquakes, rain, snow, and extreme temperatures can put extra stress on the structure.
Why Choose Structural Concrete?
How do you know if concrete is the best material for your project?
Take into consideration these benefits of using concrete:
Since concrete is so abundant, this keeps your construction time relatively short. That said, you won’t waste time waiting for delivery from far away or run into a lack of material.
Another impressive aspect of concrete is that you can invest in more as needed. Doing so keeps the construction site cleaner and more organized.
Concrete is a fire-resistant material. This fire resistance keeps insurance costs low and protects your investment from this danger.
There will also be little need for structural repairs due to fire damage.
When reinforced, concrete has a high tensile and compressive strength.
Concrete structures are durable even under extreme conditions. They can withstand earthquakes, snow, and high winds.
Concrete can also resist corrosion from chemicals in the water, and it’s often the only material used for projects submerged in water.
When constructing your project according to the model code, you’ll face fewer concrete repairs due to shrinkage.
Cement often consists of recycled material like fly ash, glass, and pieces of tires.
It’s also possible to crush, recycle, and reuse cement for other purposes, such as roads and parking lots.
Concrete is cheaper to acquire than many other materials.
Its sustainability also makes it more economical. It’s a long-lasting material with minimal maintenance cost.
Concrete structures require less skilled labor costs for construction, so you also save money that way.
Concrete has the unique advantage of using admixtures. Aggregate is a common additive to concrete, but many more options exist.
You can then use these admixtures to overcome potential challenges. For example, they can speed up curing times, solve weather challenges, and inhibit corrosion due to chloride.
You can also use coatings to protect the concrete after it has cured. These coatings are often made from epoxy and can be moisture-sealing, chemical-blocking, or both.
Because it is a liquid, concrete can take on any desired shape.
Types of Structural Concrete
There are different types of methods used to construct a concrete building.
These are the most common:
A construction company builds the formwork on site where the permanent structure will be. The concrete is then poured and dried.
After removing the formwork, the concrete will cure.
Cast-in-place is the most traditional type of formwork for concrete.
With tilt-up walls, a crew will build the formwork on the ground in the desired shape of the structure. Next, they’d pour the concrete and allow it to cure horizontally.
After removing the formwork, a crane tilts the panels into place, joining them together to form a structure.
Structural Precast Concrete
The building of these structures can happen either on or offsite, forming and curing before installation. The most common precast components are wall slabs, beams, and columns.
Structural Concrete Insulated Panels
These are permanent insulated formwork that contains steel reinforcements. ICFs are popular for the building frame of the building.
Pouring the concrete into the panels provides the strength of concrete plus extra insulation. There’s also no need to remove the formwork as it becomes a part of the structure.
Structural Lightweight Concrete
Also known as thin-shell concrete, this type of structure is most common for special designs or unconventional shapes.
Curved structures or embossing and texture added to concrete structures use thin shell concrete. You can also use this special method to construct a large roof without support.
Learn more about thin-shell concrete in our article How Thin-Shell Concrete Construction Works.
What Questions Should You Ask Your Structural Concrete Contractors?
If you’ve never completed a project using concrete, yet you see its potential benefit, you may have a lot of questions.
Your contractor is the best person to answer those questions since you’ll share the project’s specifics with them.
Here are some good questions that you should be asking your concrete contractor:
1. Which Type of Structural Concrete Is Best for My Project?
Your contractor’s answer may be a bit more complex than you expect. They may even give you a choice, but they’ll provide your options based on a few different project specifications.
Some building times are shorter than others. So if your schedule is tight, your contractor will advise using a faster structural concrete type, such as tilt-up or precast.
Do you have more time? If so, your contractor could prefer cast-in-place or another type based on his experience or personal preference.
When taking location into account, you need to measure your total lot space.
For example, do you have the space for certain concrete types?
Tilt-up requires more site area for the formwork to be complete, so if your lot is small, this may not be an option.
Precast happens offsite, and cast-in-place requires little extra space.
Is the location prone to natural disasters? If so, take this into account, too.
Some concrete structures are more expensive than others. Generally, aside from cinder block buildings, ICF concrete structures are the most expensive.
Your contractor should let you know if your budget does not allow for these splurges.
If you’re constructing a large warehouse, certain types of structural concrete will work better than others. The same is true if you’re simply constructing a small shop.
Your contractor will help you decide which type of structural concrete is best for your project specifications.
2. How Thick Will the Slabs Be?
This question may sound silly, but the thickness of your concrete slabs is crucial to your project.
The optimal thickness is dependent on the size and use of the building. Thicker slabs will be stronger but will require more support. On the other hand, if the slabs are too thin, they may not be able to bear the load placed upon them.
3. Can I See Your Credentials?
This question isn’t so much about your project. But it is about whether this contractor is the right choice for the job.
You’ll always want to screen contractors before you sign an agreement.
Ask if they are licensed, bonded, and insured.
Do they hold an ACI certification? Are they a member of Fib?
These credentials prove your concrete contractor is knowledgeable and dedicated to their profession.
Ask to see their past projects and if they can provide any references. Do they provide a warranty on their work?
All these questions can help you to get a feel for the experience, expertise, and professionalism this contractor can bring to your project.
As this article brought out, there are many advantages to choosing structural concrete for your next project.
Concrete is a sustainable, economical, environmentally-friendly, and durable material that’s also readily available. You can also “boost” it through the use of admixtures applied in various ways.
However, if you choose to use concrete when building your next project, you still have many more choices ahead.
Make sure you choose a knowledgeable contractor to help you make those decisions to construct a concrete structure that will last for generations to come.
Are you ready to break ground on a brand new concrete building? If you’re in the Denver area, contact us for a job quote!