How Are GRC Planter Boxes Made?

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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. In this article we give you a step-by-step guide to how we utilise GRC technology to produce concrete planters, troughs and pots.

Precast GRC Technology Can be Applied in Two Ways

While GRC technology has revolutionized lightweight concrete manufacturing, the application process generally follows two distinct production methods depending on the required strength and design complexity

• Premix GRC Production Method

This method involves adding chopped glass fibre reinforcement into a specialised premix concrete slurry before pouring or pumping it into a mould. It is ideal for standard casting requirements and consistent wall thickness.

• Spray-Applied GRC Production Method

This method uses a specially designed concrete spray gun that simultaneously chops and blends glass fibre reinforcement into a scientifically formulated concrete slurry as it is sprayed into the mould. This technique typically provides GRC with greater flexural strength than the pouring method because the process enables the glass fibres to be layered two-dimensionally rather than three-dimensionally.

Why Manufacturing Quality Matters for GRC Planters

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.

Step-by-Step Summary of How GRC Products Are Actually Made

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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, 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 utilises 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.

Making the Mould for a GRC Planter

Satu Bumi 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 has a significant effect on the ultimate quality of a GRC casting. Therefore, Satu Bumi utilises 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 glassfibre slurry into moulds before demoulding and curing.

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.

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 is 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 and 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.

Staging Custom GRC Planters

Staging is Satu Bumi’s final quality control process for custom planters that require a high level of precision, shop drawings compliance and pre-planned on-site interconnection.

During staging, apart from leveling and general final quality control, all measurements are checked against the shop drawings and the planters are staged against each other to ensure they fit together as intended. Finally, the planter numbering is checked to ensure it is in accordance with the project plan for installation management.

This part of the quality control process is essential for professional landscaping projects with custom planters.

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.

Transporting GRC Planters

Transportation is typically an important and expensive element in sourcing GRC products. Therefore:

• For wholesale distributors

  Where possible, Satu Bumi’s Distributor Range of products are designed for nesting and for efficient paletisation and containerisation. Also, distributors have differently priced packaging options that include “clean skins packaging”, “robust timber packaging”, and “premium heavy-duty cardboard and timber packaging”.

• For commercial projects

  All CityScape commercial orders are packaged in “premium heavy-duty cardboard and timber packaging”. In addition, all CityScape commercial orders for the Australian market are generally shipped from the factory to our warehouse facilities at the customer’s nearest capital city port. Therefore, since our customers only pay for the transport from the port, Satu Bumi’s transport charges are generally less expensive than the cost of interstate road transport from our Australian based competitors.

Satu Bumi is Committed to 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.