Concrete Construction
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Concrete Construction
One of the most common construction materials is concrete. This material is made up of cement, fine aggregates (usually sand), and a mixture of coarse aggregates and water [1]. This material has special properties, such as strong durability and can withstand high temperatures.
Concrete can be used for foundations, columns, beams, and more, making it a useful construction material [1]. There are two types of concrete construction - pre-cast and cast-in-place. They are different in how and when they are done in the construction process and each have their benefits and disadvantages. The circumstances in which they are used are elaborated upon in the later sections.
Pre-cast concrete in varying shapes and sizes [2]. |
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Advantages of Concrete Construction
Concrete construction offers a variety of benefits compared to other construction materials and techniques [3]:
- Strong durability
- Maintenance cost is low
- Can be cast into any shape
- Withstand high temperatures
Disadvantage of Concrete Construction
Concrete construction also has some disadvantages that are worth mentioning [4]:
- Tensile strength is low. For places with earthquakes, concrete cannot be the only material used for the foundation.
- Concrete production represents 4-5% of global carbon emissions, which impacts our environment and contributes to climate change [5]. Compared to other construction methods, the environmental impact of concrete is significant [5].
Cast-in-Place
This method involves having concrete in an unhardened state that is brought into a construction site, then placed into the required location [6]. This method is necessary for the foundation and concrete slab.
This type of concrete is delivered to the site by a concrete truck, which pours concrete into the required location using a chute. It is best practice to pour concrete when weather conditions are favourable (sunny, dry day), otherwise moisture may affect the curing process.
There are certain scenarios where cast in place is not possible. For instance, cast in place cannot typically happen in a river. Other construction methods may be used to solve this problem.
For more information, go to the Foundations wiki page.
Cast-in-place concrete at a construction site [7]. |
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Curing Process
Curing is a chemical process that occurs when there is a change in state of the material from liquid or semi-liquid to solid [8]. This usually applies for cements; however, there are other materials that experience curing. When curing occurs, it usually takes three days to two weeks to solidify [8]. It should not be rushed as it may become too porous, leading to potential structural strength problems. Construction that uses cast-in-place concrete cannot move forward with the construction process until the concrete is dry.
A strength test is done after the concrete is poured to ensure the curing process is complete.
Strength Test
Once the concrete is done being poured, the strength may change from what was predicted. If the strength test results are below the required or expected strength, the concrete may need to be removed and replaced. Concrete that is not properly cured can lose up to 50% of its strength, durability, and watertightness [9].
A resource for the different concrete tests: Concrete Tests.
Precast
It is usually easier to put something in place that is prefabricated. Precast typically means the part is created off-site and then delivered to the site. As well, since it comes in pieces, it can be installed right away.
There are time benefits and strength benefits. First, there is more time for the concrete to solidify off-site. It is done in a controlled factory environment, avoiding unfavourable environmental conditions (e.g. rain) and uses moulds. It also cuts down the time to wait when it comes and construction site workers can use the parts right away without needing to wait.
Below is a video to show this process in construction. It will show the process of mixing the cement, pouring into a mold, and letting it dry to reach its final solid form:
Pre-cast concrete creation process [10] |
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