If the tension of concrete is large enough we get cracks. Becauase concrete is weak in tension, we have an option to put the reinforcement inside of the concrete. We can reinforce concrete with rebars. However, in rare cases when steel bars cannot be used or when the structure needs to be made thin, what should be done? How about we put fibers into it rather than put rebars?
*This content is based on Tyler Ley's youtube video "What is fiber-reinforced concrete?"
To tell the truth, it doesn't make the concrete stronger but it makes it hold together longer like the picture below: it makes it really really hard to pull apart and we call this toughness it will still form at the same load but the fibers keep the crack small.
There are two types of fibers. Micro-fibers are mixed to protect fresh concrete and should be used within 6 hours after mixing. They prevent crack formation of fresh concrete. Macro-fibers are intended to carry load and, therefore, used to replace traditional reinforcement in certain non-structural applications as well as minimize and/or eliminate both early and late age cracking.
|
Micro fiber |
Macro fiber |
|
|---|---|---|
|
Advantage |
reduces plastic shrinkage cracking |
minimizes both early and late age cracking |
|
Size |
<1/2 inches (12.5mm) |
>1/2 inches (12.5mm) |
|
Material |
flexible |
stiff |
1. Some reinforcing everywhere
2. Strength after cracking
3. Reduces damage in a fire
1. The fibers in concrete are randomly oriented, making control difficult.
Some may help me and some may not so fibers are kind of random. They are hard to predict what they're gonna do for you and this is why it's tough for some engineers to use fibers.
2. Must adjust mixture design and finishing practices
3. Fibers increase concrete cost by 10% to 15%
So far, we have explored methods of reinforcing concrete with fibers. There is also a method of reinforcement using rebar. (related post : Secrets of Reinforcement | How to design reinforced concrete)
Then, which method is better for reinforcing concrete?
It's recommended to use both. Reinforce with rebar for major loads and use fiber reinforcement to minimize cracks.
This content is based on Tyler Ley's video "What is fiber-reinforced concrete?" If you want to learn about the appropriate amount of fiber reinforcement and how fibers reduce damage in fire, please click the link to explore Tyler Ley's content.
Link : What is fiber reinforced concrete?
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