Concrete is used in a wide range of applications. Most construction projects utilize concrete, from the walls and roofs of buildings to thick dams to mind-blowing skyscrapers like the Burj Khalifa.
Due to the variety of applications, many different forms of concrete have developed. These concrete forms differ vastly in terms of their physical properties, appearance, usability, benefits, and many other factors.
One of the most popular forms of concrete is Glass Fiber Reinforced Concrete (GFRC). It is a significant improvement over traditional concrete and has been steadily replacing it in countless cases.
This article discusses GFRC in detail. We will explain what it is, how it is made, its applications and pros and cons.
What is Glass Fiber Reinforced Concrete?
GFRC stands for Glass Fiber Reinforced Concrete. This type of fiber-reinforced concrete contains glass fibers. The concrete matrix binds to these glass fibers, and the addition of glass fibers leads to improved reinforcing and mechanical properties of the concrete and higher tensile strength.
GFRC weigh less than traditional concrete panels but are stronger; hence, their popularity when additional reinforcement is necessary. Therefore, using a thinner GFRC panel instead of a bulkier panel with steel reinforcing bars leads to a saving in space.
Who invented GFRC?
Adding reinforcement to concrete to improve its mechanical properties is an old idea. Reinforced concrete was used to make historical structures like the Colosseum and Pantheon – structures that still stand today.
Initially, Type E and Type C glass were added to concrete to improve flexibility. But the experiment failed due to the resulting high alkalinity.
In the 1960s, Europe began experimenting with Zirconium-based glass that could handle an alkali attack. The experiments finally became successful in the 1970s, and it was discovered that glass with 17% Zirconium was perfect for the purpose.
How is GFRC Made?
Glass Fiber Reinforced Concrete (GFRC) is made by using the following materials:
- Fine Sand: The fine sand should be 0.4 mm to 0.5 mm, and the accepted range is 0.3 mm to 0.6 mm. Finer particles decrease the flowability of concrete, and coarser particles can be deflected after striking the surface during spraying.
- Cement: Ordinary Portland cement is acceptable for making glass fiber-reinforced concrete. The weight of cement is usually equal to the weight of the sand used.
- Polymer: There are many types of polymer and concrete matrix mixtures, such as Ethylene Vinyl Acetate (EVA), Styrene Butadiene Rubber (SBR), and Acrylic polymer. Acrylic polymer is the preferred choice for glass fiber-reinforced concrete. The weight ratio of polymer to concrete is usually 6 grams of solid polymer per 100 grams of the cementitious mixture.
- Water: The water content in the concrete mix is critical, as too much water can ruin the mixture. It is essential to consider the water content of the polymer mixture to determine the overall water content. The ratio of total water to concrete should fall between 0.30 to 0.35.
- Admixtures: Manufacturers produce various admixtures to use in GFRC. Common admixtures are silica fumes and superplasticizers.
- Glass Fibers: The addition of chopped-up alkali-resistant (AR) glass fibers is the defining factor of glass fiber-reinforced concrete. The amount of glass fiber will vary based on the type of manufacturing method used, as discussed below.
Sand, cement, polymers, water, and admixtures are also common in other types of reinforced concrete. GFRC is unique in terms of materials because of the addition of glass fibers.
There are three manufacturing methods for Glass Fiber Reinforced Concrete:
Spray-up GFRC is the conventional way to create precast concrete panels. In this method, the Glass Fiber Reinforced Concrete is sprayed into a mold by hand.
A concentric chopper spray gun is used to spray long glass fibers into the concrete mix. The mixing occurs in the gun’s nozzle.
On average, this method contains a glass fiber content of about 5%, a higher fiber content than the usual concrete premix. This method requires skilled labor to be successful, and good quality equipment and quality checks of the work in progress.
The defining factor of vibration casting is the use of premix concrete. The premix concrete mixture is poured into a mold. Then the mold is vibrated so that the concrete achieves consolidation.
This method is simpler and cheaper than sprayed GFRC. However, the molds in this method should be watertight. Vibration casting should not be used with rock molds.
Hybrid casting is the combination of spray-up and the use of a premix. A specialized spray head using a peristaltic pump is used to spray the concrete.
Hybrid casting introduces the benefits of spray-up GFRC and vibration casting. While sprayed GFRC requires highly skilled labor, hybrid casting is possible with moderate skill.
Due to using a spray instead of vibrations for the premix, the strength of the resultant concrete panel is higher than the vibration casting methods.
What Are the Physical Properties of Glass Fiber Reinforced Concrete?
Glass fiber reinforced concrete (GFRC) is well known for its high compressive strength-to-weight ratio. This benefit results from the high cement mixture and low water content.
Other benefits are its high flexural strength (bending strength) and high tensile strength.
GFRC also has appreciable load-bearing qualities. The direction resistance to load bearing is highly versatile, depending on the orientation of the glass fibers. Additionally, to bring out the high tensile strength of GFRC, it is vital to ensure that the fibers are stiff.
The primary purpose of the fibers is to provide tensile strength in lightweight panels. The addition of acrylic polymer enhances the flexural strength of the GFRC.
How Thick is GFRC?
The minimum thickness range of GFRC varies between 3/4″ to 1″. If the thickness goes below this limit, there is a chance that the concrete panel may break during transportation or handling.
The minimum thickness possible with GFRC is lower than conventional concrete (1.5″ to 3″). This is an excellent benefit since the thinner GFRC panels provide the same strength as traditional concrete panels.
What are the Benefits of GFRC?
Glass Fiber Reinforced Concrete (GFRC) is better than many other concrete variants due to reasons such as:
The GFRC components used to construct lightweight panels are non-flammable minerals. In addition, the face coat of concrete protects against fire and acts as a temperature regulator.
Glassfibre-reinforced concrete is lightweight, especially when compared with conventional concrete. Additionally, thin wall casting applications provide the benefit of easy installation.
GFRC molding covers a range of applications, such as GFRC countertops, columns, panels, domes, and more. Various shapes are available for immediate order from Premier Precast.
Various Price Points
The three manufacturing methods have different prices, with sprayed GFRC being the most costly, vibration casting the cheapest, and hybrid casting the midpoint between the two. Therefore, buyers have many options and can find a balance between cost and strength parameters.
Directional Load Resistance
Glass fiber reinforcement results in incredible strength and flexibility. It is possible to achieve load resistance in GFRC by adjusting the fiber orientation. This feature makes GFRC components very flexible and customizable to individual requirements.
No External Reinforcement
GFRC contains glass fibers internally to provide reinforcement. Therefore, further strengthening measures, such as steel reinforcing, can be avoided in later stages of construction. Lightweight GFRC panels are an easy buy-and-install fix.
Spraying is a critical part of GFRC manufacturing. Due to the spraying action, defects such as voids or cracks do not appear on the concrete surface, unlike normal concrete. Spraying also enhances the finish of the final concrete countertops or panels.
Due to the fiber coating of GFRC, the alkali-resistant fibers act as extra protection. The resulting panels resist rain, moisture, alkali attack, corrosion, or other environmental issues.
What are the Basic Uses of GFRC?
There are many applications and projects where glass fiber-reinforced concrete is the ideal choice. Some of these applications are:
- Concrete Countertops: GFRC countertops are becoming more and more common today due to their high aesthetic appeal and crack resistance. Color pigments can make countertops match the required color.
- Wall Panels: GFRC wall panels provide a beautiful look while reducing the overall weight. These panels are long-lasting as well as decorative for home and office interiors.
- Concrete Dining Tables: Nowadays, it is common to see concrete dining tables in restaurants and houses. The concrete for these dining tables is GFRC due to its lightweight nature and high sheen. In many cases, integrated countertops and dining tables create a beautiful kitchen island design.
- Fireplace Surrounds: Due to the flame-resistant nature of GFRC, these panels are ideal for fireplace surrounds to create an attractive interior design. GFRC components are also well-suited for creating fireplace hearths and mantles.
- Outdoor Furniture: GFRC is resistant to adverse environmental conditions. Therefore, GFRC furniture, such as tables, benches, and chairs, is an excellent choice for outdoor places like parks.
How Much Does GFRC Cost?
The cost of GFRC depends on many factors, such as:
- Whether you want GFRC precast or GFRC premix. Precast GFRC comes in a ready-to-install form matched to your required shape. In the case of GFRC premix, you will need to hire an expert who can use it correctly. Correct proportions and casting methods are crucial, and the tiniest oversight may ruin the final result.
- The GFRC manufacturing method. Hybrid, sprayed, or vibration casting? Hybrid is the go-to choice for most people since it offers a good balance between price and strength.
- The thickness and area of the GFRC panels.
The cost of GFRC generally comes as a price per square foot for a given thickness of GFRC. For an accurate idea about how much GFRC will cost you per square foot, you can read our detailed guide on GFRC pricing.
Does Glass Fiber Reinforced Concrete Have Any Disadvantages?
The mechanical properties of GFRC make it ideal for various requirements. However, one potential disadvantage for some users is the cost of GFRC.
GFRC can be expensive to use when compared to ordinary concrete. Of course, the added cost comes with additional strength and several other benefits, already mentioned in previous sections.
How Does Glass Fiber Reinforced Concrete Compare to Its Alternatives?
Reinforced concrete can have different types of fibers, such as steel, plastic, carbon, or glass. The different kinds of fibers impart specific characteristics to the reinforced concrete.
GFRC uses glass fibers. Glass reinforcement adds lightweight characteristics, strength, and aesthetics. With plastic fibers, concrete will have extreme cold resistance and flexibility. Carbon fibers make the concrete more chemically resistant. Steel fibers add durability and crack resistance.
Among other alternatives, such as UHPC, cast stone, and natural stone, GFRC is the top choice when a high strength-to-weight ratio is required.
How to Choose GFRC Products?
When choosing between different GFRC products and manufacturers, there are certain factors to consider:
The whole purpose of utilizing a precast glass fiber concrete panel is that you can customize it as per your requirements. Therefore, factor in the customization options that the manufacturer offers. Good GFRC manufacturers can create even the most complex GFRC assemblies with integral metal framing.
Type of Panels
GFRC panels come in two types:
- Panelized GFRC panels: Panelized GFRC contains many individual components connected to form one larger panel. It has greater strength than a non-panelized GFRC panel. In contrast, a non-panelized panel is one single piece.
- Non-panelized panels: Non-panelized panels are great for adding adornments that don’t require as much strength. Prices for non-panelized panels are cheaper than those for panelized panels.
A reliable GFRC supplier will supply the GFRC precast panels to your doorstep or the construction site, wherever you require them.
Which GFRC Supplier to Choose?
Premier Precast is one of the highest-rated suppliers of GFRC panels in the USA. It provides panelized and non-panelized GFRC as required. Premier can match panelized and non-panelized panels to any customization and size requirements. You can contact a Premier Precast expert for any custom requirements or price quotations you need.
Adding glass fibers to ordinary Portland cement was an innovation that took a lot of time and research to do right, but the time spent was worth it.
Glass fibers enhance the properties of Portland cement like nothing else, making concrete lighter than before.
More and more builders and architects are becoming aware of the properties of GFRC and utilizing this concrete mix in their structures.
If you need strong and lightweight concrete, GFRC precast might be the ideal material for your project. You can browse the Premier Precast catalog to learn about the different GFRC products available.
Frequently Asked Questions
Here are the answers to some frequently asked questions regarding GFRC:
How durable is glass-fiber reinforced concrete?
Besides glass fibres, GFRC utilizes low-alkali cement and pozzolans that increase durability significantly. Its durability is more than that of ordinary concrete and precast stone.
Is glass fiber concrete safe?
Yes, glass fiber-reinforced concrete is safe to use. This type of concrete is much safer than many other construction materials due to added safety benefits, such as being resistant to fire and adverse climates.
Does GFRC crack?
No, GFRC does not crack due to the process used for making GFRC. Instead of directly pouring a fluid concrete mixture into a mold, GFRC is sprayed into the mold by special sprayers. Spraying makes the GFRC more adhesive and resistant to cracking in the short or long term.