Concrete is one of the world’s most ubiquitous building materials, with over 500 million tons produced annually in the United States alone. Its stiffness and compression strength lend themselves to reinforcement — an integral element of the construction process. However, knowledge of correct fiber types and quantities is essential to achieve optimal results.
Project engineers and designers have two principal reinforcement choices — fiber and rebar. Each has strengths and weaknesses in various applications, and understanding these differences is critical to making the right choice for your next project.
Types of Concrete Fiber Reinforcement?
Fiber-reinforced concrete, also known as no-rebar concrete, is a concrete mixture combined with fibers of various materials to provide post-crack strength and enhance durability. In essence, fiber-reinforced concrete performs the same function as a reinforcing bar (rebar). When it dries, the fibers create an internal mesh that can withstand challenging applications such as pavements.
Adding fibers to concrete increases its overall structural integrity and energy absorption. This mixture is relatively easy to create. Ensuring the fibers are evenly distributed through the mixture is essential for regular mixed concrete or mortar applications. The percentage of fiber in the concrete varies depending on the type of fiber and intended application. These fibers increase concrete durability, longevity, and crack control, making no-rebar concrete a popular option for many construction projects.
Some common types of concrete fiber include:
Cellulose: These fibers are constructed from processed wood products to control and mitigate plastic shrinkage cracking.
Polyvinyl alcohol: These fibers can alter concrete’s compressive and flexural performance at higher volumes.
Glass: Glass-fiber reinforced concrete (GFRC) is common in architectural applications because it is lightweight, durable, and non-combustible.
Steel: Steel fibers can elevate concrete’s post-crack load-carrying capacity and be shaped into various geometries to meet the needs of multiple applications.
Micro-synthetic: These fibers are used in applications where the protection and mitigation of plastic shrinkage cracking are essential. Most are manufactured from polypropylene, nylon, polyethylene, and other synthetic materials.
The Advantages and Disadvantages of Fiber-Reinforced Concrete
Fiber-reinforced concrete has several distinct advantages in various construction projects, including:
Crack prevention: As moisture evaporates from a concrete mix, concrete slabs can fall prey to shrinkage cracking. Fiber-reinforced concrete provides superior crack control, preventing cracking in the construction phase. This additional structural integrity leads to a higher-quality finished product.
Strength and durability: Adding fiber to concrete increases its overall durability, lowers corrosion levels, and improves its tensile strength compared to unreinforced concrete.
Ductility: Fiber-reinforced concrete can withstand significant tensile stress before exhibiting signs of damage, increasing the structure’s weight-carrying capacity.
Flexural strength: Fiber reinforcement significantly improves the flexural strength of concrete, which is essential for areas that must withstand heavy loads and surface movement.
Freeze and thaw resistance: The mesh reinforcement inside the concrete structure prevents cracking due to expansion and contraction in varying temperatures.
Appearance and longevity: Reduced shrinkage and cracking improve concrete longevity from the outset. In addition, fiber reinforcement can minimize the need for expansion joints, resulting in a smoother aesthetic.
Despite its many advantages, concrete fiber reinforcement has some considerations:
Uneven distribution: If operators mix the concrete correctly, it can lead to better distribution and improved concrete quality. Ensuring even distribution requires skilled and knowledgeable workers.
Upfront investment: Fiber-reinforced concrete can be costlier than other alternatives, such as rebar.
What Is Rebar?
A reinforcing bar comprises metal rods placed inside concrete to improve its resilience and crack resistance. Several types of rebar exist, from carbon steel to stainless steel. It provides additional durability and is common in critical parts of structures like foundations and columns. In areas where high-impact loads are expected, rebar adds compressive strength to concrete and improves its ability to withstand impact without fracturing. It also prevents localized stress concentrations that can lead to structural instability or failure.
Concrete has excellent compressive strength but relatively low tensile strength. Steel bars are placed in a grid pattern within the concrete, maximizing stability and minimizing load disruption. The thicker the rebar and the more frequent the placement, the stronger the end product. Rebar allows the concrete to withstand vertical and horizontal forces by distributing the force through the concrete rather than allowing it to penetrate and crack.
The Advantages and Disadvantages of Rebar in Concrete
Rebar is a traditional form of concrete reinforcement, and many of its advantages are still relevant today.
Strength and durability: Rebar significantly improves concrete’s tensile strength, making it more suited to handling heavy traffic over time.
Stability in variable weather conditions: Freeze-thaw cycles can negatively impact concrete structures. Rebar stabilizes concrete during inclement weather over long periods and reduces the risk of cracks and structural damage.
Cost-effectiveness: Rebar has been a dependable solution in construction for many years, which means it’s easy to buy for a reasonable price.
Elasticity: Steel rebar has a high modulus of elasticity, meaning it can stretch in tension under heavy loads and regain shape after the load is removed.
Rebar suits many applications due to its immense strength, but only some concrete projects require it. Despite its strength, rebar also presents some drawbacks to consider:
Limitations at high temperatures: Steel rebar will liquefy at extremely high temperatures, which can pose a safety risk in specific applications.
Cracking and reactions: Minimal concrete over the rebar allows water to penetrate and react with the steel. Over time, this reaction causes the concrete to crack. Concrete aggregates can also react with the steel, causing the concrete to spall.
Corrosion: Steel exposed to the elements will rust, reducing the overall strength of the reinforced concrete. A buildup of rust around rebar causes considerable pressure on the surrounding concrete, leading to cracks and eventual failure.
Weight: Rebar adds significant weight to concrete materials, rendering it unsuitable for specific applications.
How to Choose the Best Solution for Your Project
So, is fiber better than rebar in concrete? The answer depends on several factors, including your budget and project type.
Fiber could replace traditional steel-reinforced concrete in many applications, assuming the correct fibers are used for the job. Fiber-reinforced concrete can possess performance characteristics that meet or exceed the specifications of steel reinforcement, especially regarding secondary reinforcement slabs such as pavements.
When you’re choosing between the two, keep these points in mind:
Project priorities: Project parameters significantly influence concrete reinforcement choice. Rebar provides excellent load-bearing capacity and stability, making it ideal for applications that encounter heavy traffic or challenging soil conditions. Fiber-reinforced concrete enhances flexural strength and crack control, making it suitable for projects in which durability and shrinkage cracking resistance are priorities.
Construction timelines: All construction projects require a balance between quality and efficiency. Installing rebar requires precise placement of the steel bars, which can be labor-intensive and time-consuming. Incorporating fiber mesh into your cement mix can be quicker.
Budgetary considerations: Your choice of reinforcement also depends on your budget. Fiber can seem expensive compared to rebar, but you need to use less to boost concrete strength and durability.
Find the Right Reinforcement Option for Your Next Project With FORTA
Fiber mesh concrete is easy to work with and offers many of the same benefits as rebar, alongside some additional advantages. The key is to use the right fiber for your application. At FORTA, we have manufactured and distributed fibers for various applications since 1978. Today, we supply quality synthetic reinforcement fibers to the global construction industry, where we are a trusted partner to many organizations.
We believe in providing Stronger Lasting™ roads, bridges, and buildings worldwide. Our pavement toolkit offers advanced concrete engineering for durable and long-lasting solutions that reduce construction and maintenance costs while maintaining overall project quality. Contact us to learn more about reinforcement that lasts!
