A Practical Guide to GRC Spray Guns
The Right Tools for The Right Techniques
Whereas traditional concrete is typically poured, Glassfibre Reinforced Concrete is generally sprayed due to the often-complex nature of GRC products. Specialist spray guns are required for such a task, designed to align with the production processes of GRC and to accommodate the incorporation of the composite’s key component: AR Glass Fibre.
Before beginning the production of GRC, prospective manufacturers must decide the method of production they intend to use as this methodology will dictate which spray gun is best suited for their production needs.
GRC Production Methods
GRC’s unique set of properties are influenced by several parameters, including water:cement ratio, porosity, fibre content, orientation and length and, notably, the method of production.
The two most popular methods of production – Traditional Hand Spray and Sprayed Premix – both require spray guns specifically engineered for each method. For custom designs and architectural elements demanding high AR Glass Fibre percentages and intricate detailing, Traditional Hand Spray is the most suitable option. For standardised products with an emphasis on efficiency and consistency, Sprayed Premix offers a more practical solution.
To enhance the appearance of GRC products, surface finishes, ‘mist’ and facing coats are applied during production which also require the use of specialist spray guns.
Given the distinct characteristics of each method of production, choosing the right spray gun is essential in ensuring production efficiency and achieving optimal product performance. As a guide, we’ll break down the most suitable GRC spray guns for each production method in the following sections.
Traditional Hand Spray:
Concentric Spray Head
Starting with the pinnacle of GRC spray gun technology, we have the Concentric Spray Head.
This spray gun is used for the most popular method of GRC production: Traditional Hand Spray, in which cement/sand slurry and glass fibre are projected from the same nozzle, ensuring efficient and even distribution.
The precise engineering and innovative design of the gun streamlines the production process. Glass fibre roving is fed through the gun and cut to length within the rear chopper mechanism whilst compressed air propels the chopped fibres through the atomiser body nozzle. Simultaneously, slurry is conveyed to the nozzle from the pump and is emitted from an annulus surrounding the fibre. Compressed air – supplied direct from the nozzle – atomises the slurry and the two materials are projected as a composite.
Designed with convenience in mind, the Concentric Spray Head is lightweight and simple to maintain, featuring flexible airlines and a remote start/stop function for the spray station with other controls located on the boom. A water flush facility – controlled from the overhead boom – is fitted as standard.
Sprayed Premix:
MK5A Premix Spray Gun
As the name implies, the MK5A Premix Spray Gun is the ultimate tool for spraying Premix GRC – lightweight, simple to operate and very easy to maintain – it embodies everything a spray operator requires for efficient Sprayed Premix production.
In the pumping and spraying of GRC, the importance of minimising interruptions to the smooth flow of material cannot be understated – the MK5A is designed with this as a key consideration. From the gun inlet through to the specially developed premix nozzle, a clear open passage is maintained. The spray air is added only at the nozzle, ensuring an even spray distribution without interruption to material flow.
Surface Finishes & Facing / Mist Coats:
MK3 Powertex Spray Gun
Where special surface finishes are required, the hopper-fed MK3 Powertex Spray Gun is what you need. Thanks to the gun’s intuitive design, operators can rapidly and economically apply a wide range of finishes and spray ‘mist’ and facing coats. Unlike the rest of our range, this spray gun is gravity-fed and doesn’t require a spray station to operate, making it suitable for smaller-scale production specialists.
The MK3 Powertex Spray Gun is easy to operate, enabling a range of finishes to be achieved simply by selecting the correct size of nozzle, adjusting the trigger displacement and regulating the air pressure. Maintenance is just as easy: to dismantle and clean the gun, operators simply have to undo one thumbscrew.
The gun is incredibly versatile, aside from mist and facing coats, it can also be used for:
- Cement paints
- Vermiculite and perlite mixes
- Aggregate loaded resins
- Veneer and plaster finishes
- Stone paints
- Cementitious mixes
- Emulsion paints
- Non-slip deck coatings
Facing / Mist Coats:
LW Facing Coat Spray Gun
The Lightweight (LW) Facing Coat Spray Gun is likely the most popular ‘pump-fed’ facing coat spray gun in the GRC industry. The gun is used for the smooth application of the initial ‘non-reinforced’ surface layer (mist coat) and pumpable facing coats. These are sprayed directly onto the mould prior to the GRC backing.
The LW Facing Coat Spray Gun is designed to be used with the Power-Sprays range of spray stations – PS38, PS9000 and PS10,000 series. Alternatively, the gun can be used ‘on-site’ with the PS2000 and PS4000 spray machines to apply a range of concrete repair, protective coatings and other specialist cementitious materials.
Traditional Hand Spray Alternative:
LW Combination Spray Gun
For Traditional Hand Spray GRC, the LW Combination Spray Gun can be used as an alternative to the Concentric Spray Head; however, it’s mostly recommended for spraying Glassfibre Reinforced Gypsum and other fast-setting materials.
The gun consists of a glass fibre chopper and a slurry gun mounted on a single bracket. The angle of these two components can be varied to adjust the spray pattern. By just using the slurry gun, operators can also spray fine mist coats.
Cementitious or gypsum slurry is supplied via a pump and flexible hose to the slurry gun where it is atomised by compressed air and projected as a ‘slurry cone’ through the nozzle. The glass fibre roving is cut to length within the chopper mechanism from which it is blown into and mixed with the slurry, forming a sprayed composite on the mould surface. After spraying the GRC or GRG, the composite is consolidated by roller compaction.
Since the slurry gun can be easily dismantled and cleaned, the LW Combination Spray Gun is ideal for spraying fast-setting materials. It is also useful when oversized (2-3mm) particles may be present in the sand as these will not block the slurry gun.
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Automated Spraying
Looking to the future, there’s potential for these spray guns to be used in automated production processes. With recent innovations in robotics, these systems could be incorporated into modern GRC equipment, streamlining the spray process.
There has been some development in several universities to varying degrees of success; however, there remains several obstacles in the way of further progress. The main challenges at present are the need to manually compact the GRC 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 GRC would be economically viable.
However, as robotic systems continue to improve along with the exponential growth in the abilities of AI systems, it’s likely that new, more viable in-roads will be made in automating the GRC spray process.
Conclusion
At the forefront of the Power-Sprays range of GRC production equipment is our specialist GRC Spray Guns. With thousands of hours invested in research, experimentation and development, these tools have been meticulously engineered to meet the needs of spray operators.
From the hopper-fed MK3 Powertex Spray Gun through to our signature Concentric Spray Head, our GRC Spray Guns ensure excellent performance, ease-of-use, reliability and simplified maintenance throughout the production process.
If you want to learn more about our range of GRC spray guns or perhaps want to get a hands-on demonstration at our UK-based factory, get in touch: info@power-sprays.co.uk
There’s more to Power-Sprays than just GRC spray guns, you can find the full range of our GRC production equipment and materials by clicking the links below:
