GFRC stands for Glass Fiber Reinforced Concrete. It is also known as GRC in Europe. GFRC is a family of materials based on a cement/sand mix with other additives such as plasticisers and polymers. The term usually applies to a 1:1 sand:cement mix homogeneously reinforced with 1.5->5% of Cem-FIL AR fibers supplied either as continuous filament rovings or pre-chopped strands

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A specially developed mixer and probably spray equipment depending on the end product. Raw materials also needed include Cem-FIL AR glass fibers, cement, sand plus additives such as superplasticisers and polymer. Mold can be produced with wood, steel, FRP or elastomeric compounds.

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Cement has a very high pH [alkalinity] which will totally destroy conventional glass fibers which are used to reinforce resins. AR glass have been specially developed for use in high aggressive cement based matrices or composites.

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AR glass fibers are 3 times stronger than steel and have a modulus 10 times that of the commonly used plastic fibers. They disperse easily and bond well to cement making them an ideal reinforcement for mortars and concrete. Please visit for additional information.

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What is the typical and maximum amount of AR glass I can include in my mix?

Usually 1.5% to 5% are recommended depending on the final products and the required properties but greater quantities can be used for special applications. The more fibers are added to the mix, the stronger will be the ultimate product.

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What length of fibers should I use in my mix?

It all depends on the production method and finished product. Generally, ¾" length is recommended for premix [fibers added directly into the cement mix] and 1 ½" length for the simultaneous spray method.

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Premix is the process of adding pre-chopped fibers into the wet cement/sand mix at the end of the mixing cycle. This mix can then be cast, like concrete, or sprayed [spray premix] through Spray-Tech’s specially developed equipment. Simultaneous spray uses continuous strand fibers which are fed into a hand held chopping gun. This strand is cut and sprayed out at the same time as a second gun sprays out the wet mortar. Each process has its own advantages and disadvantages and these will be explained by Spray-Tech.

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They require different types of equipment. For spray premix, the equipment can be simpler and more versatile. The main difference is that chopped fibers are added to the wet concrete. Mix designs can also be different and fiber content is usually less.

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Key advantages are:

• Manpower is reduced and less skilled labor is required.

• Less material is lost from over spray.

• Spray gun is smaller allowing entry into closed molds and complex shapes.

• The fiber being included in the wet mix eliminates dry fibers being blown into the corners of the molds and reduces the amount of compaction during production

• Equipment maintenance is easier and cost is reduced.

• Ability to make complex shapes even with molds with limited access.

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Can I get the same mechanical properties between the two spray processes?

No. Premix will give properties lower than those of simultaneous spray. This can be taken into account by increasing thickness at the design/development stage or by positioning reinforcement such as Cem-MESHâ or Cem-MATâ .

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There are limitations with the production of large GFRC panels. 60 square feet would be the largest recommended size panels produced with spray premix. However, a typical mix design with an additional reinforcement such as Cem-Meshâ or Cem-Matâ offers higher mechanical properties. Additionally, an experienced design engineer should be consulted for large panels.

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I have heard different stories about the best length of fiber. What is your recommendation for regular premix spray?

Spray-Tech has developed a mix which uses 2 different fiber lengths so as to optimize workability and ultimate strength. Details can be supplied as part of the back up technical service to Spray-Tech customers.

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Full training will be given but generally water and polymer are added first followed by the sand, then cement and finally the fibers. Mixing sequence highly depends on the type of mixer and the grade of sand used. Spray-Tech can further assist in mix design and mix sequence.

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A typical USA mix will be based around 94lbs of cement with 80lb GRADED sand. Polymers are also recommended plus additional water to make it up to a w/c of 0.31-35 [depending on product and mold type]

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Spray-Tech pumps are extremely versatile. They are made to handle the full range of GRG and GFRC mixes and also the aggregate facing mixes frequently used (up to an aggregate size of 3/8").

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Spray-Tech machines offers greater versatility and productivity. They are more powerful and robust which leads to higher output. Cost is competitive and value for money is also greater.

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You buy not only the equipment but also nearly 100 years of combined experience in all aspects of GFRC production and applications. In addition, Spray-Tech are able to draw upon the combined experience of the other principal suppliers via the GFRC ONE Alliance. Spray-Tech do also offer to new manufacturers a GFRC Turnkey Solution which includes all necessary products and services required to start GFRC production within a few weeks. Please refer to for additional information.

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GFRC One is an Alliance of the premier suppliers of the materials, equipment and services to the GFRC industry. By pooling their knowledge and expertise, we are better able to serve the needs of our customers.

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After use, the hopper and the pipes needs to be washed out following Spray-Tech recommended operations manual. It is also necessary to check fluids in gearbox and grease points.

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Why is the maintenance cost of the peristaltic pump half the cost of other equipment?

There are less moving parts – no rotor/stator, augers or connecting rods to assemble and disassemble everyday. Generally speaking, the machines are more robust and have more powerful heavy duty electrical components.

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240 or 440V 3 phase at 50-60 Htz but custom specified possible. Air is 52Cu.ft per minute.

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What are the spare parts that I need to keep in order to avoid production disruptions?

For simultaneous spray equipment, a range of spare parts are needed such as air motor, blades and backing rollers for the concentric gun, and hoses, drive chains and control box for the positive displacement pump. For premix spray, the number of spares are reduced to a control box and pump hose [black] with a spare nozzle. A spare mortar slurry line is recommended for both types of equipment.

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Proper training and maintenance program plus a good sand to reduce internal wear.

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What are the main benefits of using the Spray-Tech rubber spray machine?

Less maintenance, ease of use, reduced labor and material losses. Also able to make a thinner rubber carriage via better thickness control. The machine can also be used on site to produce molds of rocks or special shapes.

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We recommend Polytek materials as a member of the GFRC One Alliance. Please refer to for information on the use of these products for molds for GFRC.

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Are Spray-Tech machines used internationally?

Spray-Tech equipment are used in South Africa, Saudi Arabia, Iran, Trinidad, Spain, Canada, Santa Domingo and in Asia.

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Via a network of agents or distributors. Click here for Purchase Order Forms.

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