GRC GUIDE
GRC Production Techniques
Learn the 4 Methods of Producing GRC
Glassfibre Reinforced Concrete’s complex set of properties are influenced by several parameters, including water:cement ratio, porosity, composite density, fibre content, orientation and length, inter filler content and notably – the method of production.
The two most popular GRC production methods used by manufacturers are the Traditional Hand Spray and Sprayed Premix techniques. As a general rule, larger items are manufactured using a poured premix method, such as Cast Premix.
Read more to learn about the 4 different methods of GRC production…
1. Traditional Hand Spray
Traditional Hand Spray is a time-tested method, used for decades in GRC production. It is the most versatile and popular production technique and the one most often chosen by new start-ups.
Through a specially designed spray gun – such as the Concentric Spray Gun – manufacturers simultaneously spray chopped AR Glass Fibres and cementitious slurry onto a mould, efficiently distributing fibre throughout the mix. This process is followed by hand compaction using a Spring Roller to ensure maximum flexural strength is achieved.
This method is known for achieving the highest strength levels, attributable to high content of AR Glass Fibre (4-5% by weight), elongated fibre lengths and planar fibre orientation.
2. Sprayed Premix
As the name suggests, the Sprayed Premix method involves the spraying of premixed GRC. Prior to spray application, chopped AR Glass Fibre and a cementitious slurry are combined before being subsequently applied using a specially designed spray gun such as the MK5A.
Compared with Traditional Hand Spray, strengths attained through the Sprayed Premix method are generally lower, mainly due to the reduced AR Glass Fibre content (generally around 3% by weight), shorter fibre lengths and a multi-dimensional fibre orientation.
Although falling short in strength, the Sprayed Premix approach excels in delivering mechanical properties that are more consistent and, in some cases, superior to those attained through the Cast Premix method. Moreover, this technique ensures uniform fibre distribution throughout the mix, resulting in GRC products that exhibit exceptional integrity and strength.
By combining the advantages of both Traditional Hand Spray and Cast Premix methods, Sprayed Premix is fast becoming the method of choice for producing a vast variety of smaller architectural items.
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3. Cast Premix
Cast Premix is the simplest GRC production method, requiring just a mixer and raw materials.
The method involves mixing chopped AR Glass Fibre into a cementitious slurry before being poured directly onto a mould. The key to getting the best results is in the speed of the mixer: running it too fast risks overmixing and adversely affecting the fibre strand integrity, whilst running it too slow risks uneven fibre distribution throughout the mix.
Once prepared, the resulting GRC mix can be poured directly onto moulds and compacted either using vibration or through admixtures incorporated into the mix design, such as Flowaid SCC.
The mix is left in the mould and cured for 24 hours underneath polythene to prevent moisture loss. After this period of curing, the product is demoulded and left to remain curing in moist conditions under polythene for a further 7 days.
Cast Premix is a favoured method for the manufacture of standardised products due to the ease of automation it offers. Even when using complex moulds, manufacturers can be assured of consistent results, although with slightly lower mechanical properties.
4. Auto Spray
The Traditional Hand Spray process can be automated or semi-automated in this method of production. Semi-automatic processes remain more common where the spray gun is mounted on a reciprocating traverse with the moulds passing underneath on a conveyor.
Compaction can be by hand or via a dewatering system. These systems are ideal for the production of flat products and can also be very versatile when used with folding moulds. Despite the advanced technologies behind these systems, they are limited in the respect that they can only spray a select range of shapes and sizes. Moreover, this method can generally prove to be expensive and inefficient for most manufacturers.
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 GRC spray applications.
Which GRC Production Technique is Best for You?
Ultimately, this decision is dependent on the specific requirements of a project.
For custom designs and architectural elements demanding high AR Glass Fibre percentages and intricate detailing, Traditional Hand Spray may be best choice. For standardised products with an emphasis on efficiency and consistency, Sprayed Premix or Cast Premix offers a more practical solution.
These different production methods can yield phenomenal results under the right circumstances. By carefully assessing project needs, manufacturers can make informed decisions on which method is best suited to deliver high-quality GRC products tailored to client specifications.
For advice and consultation, please don’t hesitate to reach to Power-Sprays. With decades of experience engineering GRC production equipment, we understand what production specialists need to produce high performance GRC products. Send us an email at:
