GRC Planters - How are they Made

In their most basic sense, precast concrete products are made by filling moulds with a wet concrete mixture and allowing them to cure. However, with the evolution of GRC concrete technology, although concrete planters are still manufactured with the use of form moulds, they can now be made to be much harder, much stronger, more waterproof and more durable. All of which are essential elements in meeting the architectural, engineering and construction standards required for concrete planter boxes, troughs and pots used in commercial landscaping projects.

Precast GRC technology can be applied in two ways :-
a) By adding chopped glass fibre reinforcement into a specialised premix concrete slurry before pouring or pumping it into a mould.
b) By spraying a scientifically formulated concrete slurry mix into a mould using a specially designed concrete spray gun that also chops and blends glass fibre reinforcement into the slurry during the spraying process. This production method typically provides GRC with greater flexural strength than the method of pouring concrete slurry into a mould because the associate production process enables the glass fibers to be layered two dimensionally rather than three dimensionally. 

Although GRC technology is an excellent material for the manufacture of very high-quality concrete planters, pots and other landscaping products, it is important to recognise that not all GRC is the same. Good GRC requires the use of the right quality raw materials, the right blending of those raw materials and the right production methodology. Cheap raw materials and undisciplined production practices need to be avoided because they more often than not result in GRC that cracks or breaks. Therefore, care should always be taken when sourcing GRC products to verify the credibility of the manufacturer.

The following is a step by step summary of how GRC products are actually made.


Satu Bumi-GRC-Planter-Engineering-Drawing

Product Engineering for a GRC Planter



The following two considerations are essential elements in the product engineering of any GRC product: -

  • Aesthetic appeal - the dimensions of a well balanced and attractive GRC product don't come about by accident. They are created at the design stage.
  • Structural Integrity - GRC products generally have a practical purpose such as holding soil and water or for seating. Therefore, they need to be more than just visually attractive. They need to be engineered to be fit for purpose.

Satu Bumi has a product engineering department that includes artisans, technicians, designers and CAD tools to produce world class GRC product designs that are both aesthetically appealing and engineered for the purpose for which they were intended.

Making the Master for a GRC Planter

A master, sometimes called a plug, is an exact physical representation of a product's theoretical design as depicted in a CAD drawing. Masters are typically made from a number of different substances such as wood, miln, clay, or even concrete and form the framework upon which a precasting mould is made. Masters become damaged and are normally discarded once they have been used to make a mould.

Satu Bumi utilizes CNC router technology in the making of masters because it provides a high level of precision. However, Satu Bumi also relies heavily on the artistic competence and experience of its master making team to get the highest quality masters possible.

Satu Bumi-GRC-Planter-Master-Making
Satu Bumi-GRC-Planter-Mould

Making the Mould for a GRC Planter

Satu Bumi's generally uses resin moulds which are made by applying many layers of gel coat, various gauges of fibreglass matting and high quality  resin to the surface of a master to create a reverse image. However, depending on the type of mould required, Satu Bumi sometimes uses rubber or wood for moulds. In addition, a variety of optional textures can be imprinted into the walls of the moulds as part of the mould making process.

The quality of a mould can have a significant effect on the ultimate quality of a GRC casting. Therefore, Satu Bumi utilizes high quality raw materials to ensure its precasting moulds are of a world class standard. 

Making GRC Planters

The actual GRC products are made by spraying or pouring a scientifically calibrated mixture of concrete and glass fibre slurry into moulds, left to cure and harden for a set time period before being demoulded and then left to continue the curing process. It is during the concrete slurry mixing stage that integrated concrete colour or waterproofing add-mixes are included.

The high quality of Satu Bumi's GRC products is dependent on properly calibrated and maintained GRC production equipment, properly trained staff, high quality raw materials and industry standard production, monitoring and quality control practices.

Satu Bumi-GRC-Planter-Production
Satu Bumi-GRC-Planter-Finishing

Finishing GRC Planters

The first step in the finishing process is to clean up any loose or sharp edges of the cast products subsequent to demoulding. After that, there are a significant number of optional stains and coatings that can be applied to the completed GRC casting including external sealants, internal sealants, graffiti protection, oxide colouring stains with either aged metal or stone appearances and high quality specialty paints.

Satu Bumi achieves excellent finishing results because we have invested significantly in sourcing the best available finishing products and implementing industry standards based finishing processes.

Packing GRC Planters

Appropriate packaging is an essential element in the preparation of GRC products for transportation to ensure they are not damaged between the factory and their ultimate destination. This is particularly important if the products need to be shipped over significant distances with the potential of several loadings and unloadings along the journey.   

Satu Bumi offers both wood and cardboard packaging options depending on the shape and size of the products or the specific requirements of the customer.

Satu Bumi-GRC-Planter-Packaging
Satu Bumi-GRC-Planter-Containerisation

Transporting GRC Planters

Transportation is typically an expensive element in sourcing GRC products in quantity. Therefore, where possible, the Satu Bumi Distributor Range has been specifically designed for optimum palletization and shipping containerisation to facilitate the maximum utilization of shipping container space.

In addition, because Satu Bumi uses shipping container efficiency for transporting our CityScape Range directly into Australia's major ports, we are generally able to transport orders from our factory to almost anywhere in Australia less expensively than the typical cost of interstate road transport.

Compliance with Industry Standards for Making GRC Products

Satu Bumi is committed to the application of industry standards in all aspects of our business where it is realistically possible, including compliance with the "Specification for the Manufacture, Curing & Testing of Glassfibre Reinforced Concrete (GRC) Products" produced by the International Glassfibre Reinforced Concrete Association (GRCA) in the UK.