If you haven’t already heard of glass fiber reinforced concrete (GFRC), then you are in for a treat.

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A very specialised type of concrete that combines cement-based composite material and alkali-resistant glass fibers, GFRC can be used for a whole host of applications due to its resilient but lightweight structure.

Interested to know more about glass fiber reinforced concrete, what it can be used for and how to make it?

Within the below guide, you’ll discover:

• What is GFRC concrete?
• What are the components of GFRC concrete
• GFRC mix designs
• A step-by-step guide on how to make GFRC concrete
• What can GFRC concrete be used for?

Ready to get started?

In just five minutes, you will know everything there is to know about GFRC concrete and its many benefits.

WHAT IS GFRC CONCRETE?

GFRC stands for glass fiber reinforced concrete and is a composite that is made up of a combination of cement, fine sand, a polymer, water, and other admixtures.

It is similar to chopped fiberglass which is used to form boat hulls and other more complex shapes, although GFRC is not as strong.

It was first created in the s in Russia, but it wasn’t until the s that it became popular in the mainstream.

There are many benefits to using GFRC, including:

• It can be used to construct lightweight panels as it can be made thinner and lighter than traditional concrete
• It has a high tensile strength
• It is more flexible than traditional concrete
• It is resistant to cracking
• It is extremely durable and can outlive steel-reinforced concrete
• It requires very little maintenance
• It is resistant to climate changes and fires
• It is cost-effective

WHAT ARE THE COMPONENTS OF GFRC CONCRETE?

To better understand what GFRC is and what it can be used for, it can be helpful to find out what this type of concrete is made up of.

1. CEMENT

Portland cement is the most commonly used cement for making GFRC concrete. It is available in white and grey. Grey Portland cement should be avoided if you want to add colour as the dark grey pigment is hard to overcome. Overall, white cement is the better option, but it is more expensive than grey.

2. SILICA SAND

Silica sand, often referred to as industrial sand, is the perfect type of sand for GFRC concrete as it helps to prevent blockages and delivers less abrasion to the equipment. It is worth noting that this type of sand can be difficult to find, although your local masonry should have some in stock.

Do not use basic playground sand, as this will clog up your equipment.

3. AR GLASS FIBER

AR (alkaline resistant) glass fiber has been used in GFRC concrete for decades due to its durability and alkaline-resistant which is a result of adding zirconia to the glass. These fibers are often used for countertops, fireplace surrounds, and other decorative applications.

AR glass fiber is available in chopped strands, in a ball of twine known as roving, and as scrim, which is a grid-like pattern that is sold on a roll.

4. WATER

When it comes to how much water to add to GFRC concrete, the less water you use, the stronger the concrete. Typically, spray-up GFRC has a low water-cement ratio. The water you use should be free from contaminants and as clean as possible.

5. FORTON VF-774

Forton VF-774 is an acrylic, co-polymer dispersion that has been specially formulated for GFRC concrete. It is also designed to be able to remain stable and durable when combined with the high PH levels of Portland cement.

Other benefits of this key component of GFRC concrete include easy spraying on vertical surfaces, UV stability, and the elimination of spider cracking and crazing.

6. PLASTICISER

A plasticiser is a chemical compound that enables the production of concrete with roughly 15% less water content. You can also find super-plasticisers that reduce the amount of water needed by up to 30%.

Plasticisers are also used to retard the curing of concrete.

7. PIGMENT

Concrete pigment is a dry powder that is used to add colour to GFRC concrete. The more pigment you use, the more intense the colour. Typically, a 5% dosage is added. Pigments are available in a wide range of colours.

 GFRC MIX DESIGNS

The GFRC mix design basically refers to the ratio that the components are mixed at. There are two different GFRC mix designs that you can choose from:

1. PREMIX

This is by far the most common GFRC mix design and is suitable for both small and medium-sized users. The premix process involves spraying through a hopper gun, with the back mix added by hand.

Premix is a much cheaper option than spray-up, although a special spray gun and pump are needed. However, fiber orientation is more random, and the fibers are shorter, which results in less strength.

2. SPRAY UP

This GFRC mix design process is far less common and is mostly used by high-end producers who use large volume spray equipment. The spray-up process is typically used for very large architectural panels and provides a higher glass percentage.

On the plus side, spray-up allows for very high fiber loads using long fibers, which results in the greatest possible strength and durability. However, the specialised equipment needed is expensive, typically over $20,000.

HOW TO MAKE GFRC

The process of making GFRC concrete is simple but must be followed in the correct order to avoid a lumpy end product. You can make GFRC concrete in a standard concrete mixer but for optimum results, opt for a high shear mixer that has been specifically designed to make GFRC concrete.

If you want to know how to make GFRC concrete or how to make GFRC panels, follow the below steps:

• Weigh or batch all materials
• Add all the liquids, including the Forton VF-774 and 2oz of plasticiser, to the mixer
• Start the mixer on slow – 300-500 rpm
• Add pigment if colour is desired
• Add the silica sand
• Add the Portland cement and increase the mixer speed to high – 1,000-1,800 rpm
• Mix on high for 1-2 minutes
• Add the remaining plasticiser to achieve the desired consistency
• Reduce the mixer speed to slow and gradually add the Premix fiber until fully dispersed

Once you have added the fiber, you must not mix for too long or at too high a speed as this can damage the fiber, resulting in placement issues and/or reduced strength.

CASTING, SPRAYING & CURING GFRC

CASTING

For casting GFRC concrete, pour the mixture into a single spot at the lowest point of the mould and allow the mixture to seek its level. After casting, consolidate the slurry and remove any entrapped air using either a hand vibrator or vibrating table.

SPRAYING

Spraying can be used for both higher volume smaller parts and lower volume applications.

For higher volume – GFRC slurry can be sprayed into molds using rotor/stator or peristaltic pumps that are specifically designed for GFRC. Whichever spray pump you use, a face coat without fiber is typically applied first. Once this has stiffened, a fiber backup mix is applied in multiple passes, with compaction between each pass.

For lower volume – A hopper gun can be used to apply face mix, and then the GFRC backup mix is applied by hand.

CURING

After placement, you should cover GFRC concrete with a plastic tarp or sheeting to prevent moisture loss and to maintain the heat of hydration. Allow the concrete to cure in the mold for between 12-16 hours. Curing temperatures should be maintained above 50°F/10°C in order to ensure proper film-forming of the Forton VF-774.

 WHAT IS GFRC USED FOR?

GFRC concrete is used in the below construction works:

• Building renovations
• Water and drainage works
• Bridge and tunnel lining panels
• Permanent formwork method of construction
• Architectural cladding
• Acoustic barriers and screens

It is most commonly used in exterior cladding. However, due to its strength, flexibility, and chemical properties, GFRC can be used for a wide range of applications.

As it can take the form of pretty much any shape or size, GFRC concrete can be found in architectural features such as moldings and landscapes. It can also be used for modular buildings, as well as walls, roofs, floors, and foundations.

In the engineering sector, GFRC is used to construct bridges, tunnels, and drainage.

It is also used as ornamental concrete to create items such as fountains, statues, domes, and planters.

For more information, please visit Jushui.

Most recently, decorative concrete artisans have started to use GFRC concrete to create decorative panels such as fireplaces, countertops, and artificial rock work.

CONCLUSION

Glass fiber reinforced concrete is lighter, faster, and stronger than traditional precast concrete.

It can be used to create almost anything that traditional concrete can, and it has the added benefit of more aesthetic options for users.

Whether you opt for the spray-up option, which uses a liquid concrete mix that sprays glass fibers, or you go for a premix in which the liquid concrete is poured into molds, glass fiber reinforced concrete is suitable for a variety of different projects and guarantees a superior finish. 

The Benefits of Advanced GFRC Equipment Explained

The Benefits of Advanced GFRC Equipment Explained

Improve Efficiency, Reduce Costs, Enhance Quality

The production of Glassfibre Reinforced Concrete (GFRC/GRC) has historically been a time-consuming and labour-intensive process which can be significantly affected by labour shortages and ever-changing health & safety regulations. Even to this day, much of the industry suffers from the inefficiencies of traditional GFRC production techniques:

• When mixing, raw materials are typically manually loaded
• When casting, material is often poured from jugs or mixing vessels
• The sprayed process is inherently labour-intensive as it requires a skilled operator

Advancements in GFRC equipment have worked to streamline these inefficient processes, greatly benefiting GFRC manufacturers by reducing the dependency on manual labour, thus increasing efficiency whilst lowering costs and minimising health & safety risks for workers.

Batching and Mixing of GFRC

With a traditional mixer and no dosing equipment, the typical mixing process is as follows:

1. Liquids are measured and added to the mixer
2. Dry materials may need to be weighed manually. Typically, it is preferable to buy pre-bagged sand and cement but in some parts of the world this is not possible or economical
3. After starting the mixer, the dry materials are lifted and emptied into the mixing vessel
4. Once mixing is complete, the mix will need to be moved to the spray station/mould and discharged manually

This long-winded and labour-intensive process can be streamlined significantly by using advanced GFRC equipment and modern batching equipment, reducing much of the manual labour typically involved.

The first step can be vastly improved by a liquid dosing system which eliminates human error and saves time when measuring liquids. A dry material batching plant offers the same benefits and more – particularly in the second and third steps – by eliminating the manual handling of materials, significantly reducing the amount of dust (in systems which are integrated with mixers) and, in many countries, saves money on raw materials as manufacturers can buy sand and cement in bulk at a cheaper rate.

Further benefits of using a batching system become apparent when factoring in its ability to batch materials in exact quantities, leading to improved consistency and quality. Materials can also be pre-weighed and discharged directly into the mixer in seconds, significantly reducing the overall mixing time. Moreover, tailored batch sizes (e.g. 75%, 80% of a standard mix) can be programmed, significantly reducing the amount of remaining mix left at the end of a shift/product and improving overall material efficiency.

Figure 1: The WAAPS is an example of a liquid dosing system

Figure 2: A complete batching plant, incorporating liquid and dry material dosing, feeding two mixers. It is also possible to automate the dosing of fibres

An analysis of a recently installed batching plant in Europe found that the slurry production had increased by over 40% whilst decreasing worker costs. There was also a noticeable increase in the consistency of the mixes as well as a reduction in the waste resulting from rejected mixes.

See the table below, an analysis comparing hand-fed and batching plant-fed mixers in a GFRC factory in Europe:

Hand-Fed Mixer Batching Plant Fed Mixer Output per day (tonnes) 6.36 9.09 Staff to manually weigh and load raw materials 2 0 Mixer Operators 1 1 Quality Control Staff 2 1 Raw material losses during production 5% 2% Slurry quality Less stable, slump varied due to human error More stable, consistent slump

Using this analysis, a cost comparison of producing slurry is shown in Figure 3 based on the following estimates for labour costs in major GFRC-producing regions of the world*:

• West Europe/North America/Australasia: $35/hr
• East Europe: $13/hr
• Middle East: $7/hr
• Far East: $3/hr

*These estimates were accurate as of January , current costs may vary

Figure 3: Comparison of production costs by region and material dosing method

Based on this data, Figure 4 shows the payback period for two types of plant:

• Compact Batching Plant, using bulk bag dischargers or 1-tonne hoppers, approx. $80,000 investment
• Large Batching plant, including silos, approx. $350,000* investment

*The actual cost of this type of batching plant varies considerably depending on the exact specification. Local costs of silos and installation can also vary.

Across all regions, the payback time on a Compact Batching Plant is much quicker than a Large Batching Plant, primarily due to the cost of installing silos. However, for larger output factories this may still be the best option.

Figure 4: Amount of GFRC production required (tonnes) to pay back a batching plant

Automated Quality Control

European Standard EN -3 specifies that the outputs of slurry and fibre should be recorded and compared in order to determine the percentage of fibre present in GFRC. Typically, this is carried out according to the GRCA Methods of Testing Part 4 – more commonly referred to as the 'bag and bucket tests', which are performed at the beginning of each shift for every spray station in use.

Whilst these tests are considered essential for quality control, they are time-consuming and prone to human error, requiring precise timing with a stopwatch to correctly measure the outputs.

Advancements in Power-Sprays GFRC equipment have worked to improve this process. The first of these advancements was to integrate automation into our spray stations which addresses the inefficiencies of the testing procedure: reducing reliance on manual timing and eliminating human error.

• For the bucket test, a dedicated button activates an LED that stays illuminated for precisely 30 seconds, allowing the operator to fill the bucket without having to keep an eye on the time (or relying on another worker for this)
• For the bag test, a 'Test Mode' can be activated for chopping the fibre which cuts the air supply to the air motor. Once the 'Start Test' button is pressed, an air valve opens for exactly 15 seconds while the operator pulls the air motor trigger and chops fibre into a bag

Whilst these advancements are a significant improvement compared to the traditional test methodology, they still take time and can only be performed while production is paused. Additionally, in some instances, the outputs can vary throughout the day due to changes in temperature, humidity, etc.

For these reasons, we decided to go one step further…

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The Fibre Loss-In-Weight (LIW) Monitoring System

This new system completely rethinks how fibre output is verified. Rather than relying on periodic manual tests, the Fibre Loss-In-Weight (LIW) Monitoring System measures fibre output directly from the roving – in real time – without halting production, transitioning quality control from a bottleneck to a seamless part of the production process.

Fibre is no longer 'wasted' being chopped solely for the bag test and time is saved by carrying out the procedure during production. Moreover, the System provides confirmation that the fibre output is correct, providing real-time feedback, allowing for adjustments to be made before the quality of the GFRC is adversely affected.

The Fibre LIW Monitoring System also records a running total of the quantity of fibre used – enabling the user to calculate waste and the true cost of the fibre used. This running total can be reset at any time whether at once per shift, per project or per day.

Figure 5: Pneumatic control panel on a modern Power-Sprays spray station showing the automated functions for bag and bucket tests

Figure 6: Prototype fibre output monitoring system – with the press of a button the current output of fibre (kg/min) will be given

Automated Spray Systems

With recent innovations in robotics, there has been a growing interest in incorporating these systems into modern GFRC equipment in an effort to streamline the GFRC spray process. There has been some development in several universities with varying success; however, there remains several obstacles in the way of further progress.

The main challenges at present are the need to manually compact the GFRC with spring rollers and the programming time required for directing the robot. These obstacles mean that there is currently a very limited number of applications where automated spraying of GFRC would be economically viable.

However, as robotic systems continue to improve along with the exponential growth in the abilities of AI (Artificial Intelligence) systems, it's likely that new, more viable in-roads will be made in using robotics for GFRC spray applications.

Conclusion

Automation technologies are advancing at an unprecedented rate, causing exponential change across industries. Yet, as has historically been the case, the construction industry remains relatively slow in adopting these modern technologies.

The GFRC industry risks falling behind if it follows this hesitant trajectory – it's more essential than ever to take advantage of new advanced production technologies and automated systems to remain competitive with alternative products.

With advanced production technologies, GFRC manufacturers can streamline the entire production process by increasing automation and efficiency. For over 50 years, Power-Sprays has been the leader of these advanced production technologies: engineering GFRC equipment that is used by the world's top GFRC manufacturers, helping them streamline production.

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