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Cast-in-Place Concrete: The Process, Benefits, and More

  • March 13, 2024

When contractors build a concrete structure, they must decide which technique to use. One of the most popular and long-standing concrete construction methods is cast-in-place. 

This article will answer:

  • What is cast-in-place concrete?
  • What are its advantages and disadvantages?
  • When is cast-in-place concrete used?
  • What is the cast-in-place construction process?
  • How does cast-in-place compare to precast concrete?

And more. 

Read on for a full understanding of cast-in-place concrete. 

Table of Contents

1. What is Cast-In-Place Concrete?
2. The Benefits of Using Cast-In-Place Concrete
3. The Disadvantages of Cast-In-Place Concrete
4. When Cast-In-Place Concrete is Used
5. The Process of Cast-In-Place Concrete
6. Cast-In-Place Concrete vs. Precast Concrete
7. Key Considerations When Using Cast-In-Place Concrete


What is Cast-In-Place Concrete?

Cast-in-place is a method of building concrete structures using removable formwork. The formwork holds the concrete that is poured directly on the construction site.

Some have other names for this method, such as cast-in-situ, site-cast, or poured-in-place. 

Cast-in-place concrete was used primarily for below-grade basement walls after the patent of Portland cement, a product and company founded by Thomas Edison.

Edison saw the benefit of using cast-in-place concrete for above-grade applications and even made entire houses out of concrete. Even though these homes were affordable and sturdy (some still stand today), society considered them too ugly.

Although this project was a failure, the idea of expanding the use of cast-in-place concrete was not. 


The Benefits of Using Cast-In-Place Concrete

Cast-in-place concrete began to spread because the many benefits this building method brought to construction projects were impossible to ignore. 

Strength

Because the result is one monolithic structural system, it dramatically increases the strength of the building. Cast-in-place concrete structures can withstand harsher weather and greater loads because they are subjected to these from the beginning.

This strategy creates a structure with high compressive strength, and when steel reinforcement is added, this also includes tensile strength. 

The combination of these two qualities makes these structures incredibly resistant to seismic and shear forces.

Cost-Effectiveness

With site-cast concrete, forms can be reused repeatedly, saving a lot of money. Since no specialized equipment is needed other than basic concrete products, there is no extra investment in this area. 

Insulation

Cast-in-place concrete walls are insulating, whether they are external or internal. The external walls provide thermal insulation from any harsh weather. Internal walls offer sound control to keep activities in each room isolated. 

This insulation also protects against mold, mildew, and insects that can damage the structure and its occupants. 

Versatility

Cast-in-place concrete forms can be customized to create concrete panels of any shape. This allows the builder to design a structure that is unique and eye-catching. Complex, curved, or irregular shapes can be formed from this method. 

Smoother Finish

Because cast-in-place concrete is made into one monolithic structure, there are no marked and unsightly gaps or cracks in the concrete. 


The Disadvantages of Cast-In-Place Concrete

While this method of building with concrete offers many benefits, it does have a couple of drawbacks. 

Labor Intensive

cast in place concrete labor

Assembling and disassembling the formwork for poured-in-place concrete requires more man hours and labor wages than other methods. Adding reinforcement bars is yet another step that tacks onto labor requirements. 

This also means that skilled workers who can perform these tasks and follow the correct procedures must create a structure that meets the required standards. 

Time Intensive

Building the forms takes time, as does waiting for the concrete to cure before removing them. On top of that, any unexpected weather conditions can delay the construction and curing process.

This can be incredibly frustrating for large projects. One delayed pour can throw off the entire schedule. 


When Cast-In-Place Concrete is Used

Specific concrete structures can be made using the cast-in-place method, including:


The Process of Cast-In-Place Concrete

When builders are using the cast-in-place method, these are the steps they take

1. Excavate and Prep Site

The site must be prepared before any forms can be built or concrete poured. When necessary, excavators are brought in to remove large obstructions like boulders, trees, and bushes. They will then level and compact the soil to create a flat, sturdy surface upon which to build. 

2. Select Formwork

Once the site is ready, the next step is formwork

Builders must choose the type of forms they will use. The least expensive are forms built from boards. Alternatively, premade formwork systems could be a good investment. 

These forms need to be designed to create the structure for which it is intended. It also must handle the pressure of the pour.

Form pieces should be determined according to these designs. Then, building the formwork with these pieces and shoring it up will create a strong mold for the concrete to dry. 

Forms should always be prepared by applying a release agent so the formwork can be reused. 

Read more: The Full Guide to Concrete Forming: 7 Questions Answered

3. Install Reinforcements

Before the concrete is poured but after the formwork is built, reinforcements should be installed. These can be either rebar or steel mesh. Deeper pours typically use rebar, while more shallow pours utilize mesh. 

4. Pour Concrete

Cement mixes bring concrete to the jobsite. Concrete is usually poured directly from the trucks to the formwork, making the process much easier and more efficient.

However, you can use a concrete conveyor or pump to get it to the formwork. Some forms may need an alternative method because the truck can’t reach them. 

A pump is always used to pour concrete into formwork on the upper levels of a building. 

5. Vibrate Concrete

Vibrating concrete is done to ensure there are no air bubbles in it. Electric or gas-powered vibrators are used on the newly poured concrete for 5-15 seconds.

The construction team will repeat this process throughout the entire pour to ensure a thorough air release from the concrete. 

It’s important to note that concrete with coarse aggregates will require more vibration than concrete with finer aggregates. 

6. Strike Off Excess Concrete

Excess concrete is removed from the top of the form to create a flat surface, which is then leveled and floated.

7. Cure and Harden Concrete

Drying times for concrete differ depending on the weather, structure size, and type used. 

While the concrete is curing, it must be kept at the right temperature and dampness. Otherwise, you risk a slab with a hundred little cracks on the surface, which is neither aesthetically pleasing nor structurally sound. 

Concrete is usually dry within 24-48 hours and cured by the 28th day. 

8. Remove Formwork

Stripping off the formwork is the last step in the cast-in-place method. The correct timing of formwork removal is crucial. It varies depending on the type of concrete used and the structure created. 


Cast-In-Place Concrete vs. Precast Concrete

The opposite of cast-in-place concrete is precast concrete, and there is much debate about which is best. The truth is that they both have benefits and drawbacks and can even be used simultaneously on the same project.

Let’s take a look at how precast concrete compares to cast-in-place

Location

Precast is made offsite in a factory and transported to the jobsite after it’s fully cured. Site-cast concrete is poured and cured onsite.

Quality Control

Since precast is made in a controlled environment under ideal conditions, it has more quality control. 

Site-casting is susceptible to elements that can result in imperfections. Temperatures can easily fluctuate, and it might be difficult to keep the concrete moist while it cures. 

Customization

Precast concrete is limited in customization because forms are reused, and concrete pieces are repeatedly made in an assembly-line fashion. Site-cast concrete allows for more customization because the forms can be built to suit the project’s needs. 

It’s possible to have precast concrete pieces specially made, but this would cost significantly more money. 

Time

Hands down, precast construction is faster. All the pieces come cured and ready to assemble. You just need to erect the precast elements and join them together. 

Site-cast concrete structures take more time. Constructing the forms and waiting for the concrete to cure adds significant length to the construction schedule. 

Cost

Precast requires a higher initial cost. Purchasing these pieces and transporting them to the job site will require a significant upfront investment. Site-cast concrete requires more labor costs overall. 

Detailed calculations must be made to determine which method will cost more in the long run. 

Which Is Best?

cast in place concrete pros and cons

It really depends on the project.

Generally, more complex projects will require cast-in-place forms to be constructed according to design. 

Precast is usually better for box-type larger buildings due to its efficiency and quality control. Since no unique shapes are required, precast pieces should work well. 

However, every project is different. Precast may not be a suitable option, even if no irregular shapes are required.


Key Considerations When Using Cast-In-Place Concrete

Considering these five factors should let you know if your concrete project is a good candidate for this construction method:

Weather

Using the cast-in-place concrete technique requires good weather, with a temperature between 68-72 degrees. 

Another aspect of weather that can affect concrete construction is humidity. The cement can lose too much hydration when the air is too dry. The ideal relative humidity for concrete construction is 50% or above.

When conditions don’t meet these requirements, controls must be put in place to protect the concrete, which can be costly and time-consuming.

Concrete Type

Some specialized concrete requires cast-in-place construction, while others are precast. There are many different types of concrete, and the correct construction method is greatly affected by which is chosen. 

Design

When the architectural design is more complex, cast-in-place should be used. Square or rectangular structures could benefit from precast construction.

Schedule

It’s important to be aware that cast-in-place construction takes longer. If the project is under a strict schedule, precast may be the way to go.

Budget

Compare cast-in-place’s labor cost versus precast forms’ higher initial price and weigh your options. Is there enough capital to shell out a lump sum for precast forms, or is it more viable to pay labor costs with time?


Conclusion

Cast-in-place concrete offers many benefits to the construction industry. 

Does your next project require cast-in-place concrete construction? Contact FMP Construction to build your next commercial concrete structure.

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