Glassfibre Reinforced Concrete is often referred to in different ways such as GRC, Glass Reinforced Concrete, Fibre Concrete or Lightweight Concrete. While the name can be interchangeable the fundamentals of well manufactured GRC remain the same and it is an amazing material for making high quality precast concrete planters.

How is GRC Made

Glass Reinforced Concrete (GRC) is essentially concrete but differs from traditional concrete through the addition of the following raw materials that provide significant value: -

Pozzolans -  to densify the concrete and minimise efflorescence

Polymers – to strengthen the concrete by controlling the curing process

Plasticizers – to strengthen the concrete by reducing the water ratio in the concrete mix

Defoamers – to densify and improve the look of the concrete by minimising air holes

Waterproofing admixes – to stop water permeation and improve freeze/thaw properties

Alkaline Resistant Glass Fibres – to provide flexural and tensile strength

Due to the amazing properties of GRC, the walls of GRC planters can be made significantly thinner than what is required for traditional cast concrete planters to achieve the same strength. Often manufactured to a wall thickness of around 1.5 to 2 cm, GRC planters can be much lighter than precast concrete products. This is where the term lightweight concrete comes from.

The great advantage of this technology is that relatively large concrete products can be made for the landscaping market that are lighter, stronger and denser than typical cast concrete products but still retain the traditional durability of concrete.

Satu Bumi’s Advanced Glassfibre Reinforced Concrete Technology is based on a combination of internationally accepted standards for the manufacture of Glass Reinforced Concrete (GRC) and Satu Bumi’s additives that provide improved concrete density and water proofing characteristics.

GRC is Durable

The fantastic durability characteristics of concrete are well known and respected as evidenced by the fact that concrete has been used for hundreds of years. This durability includes resistance from weather, water permeability, fire and chemicals. However, with the advent of GRC technology, all this can be done with much less weight and greater strength than with traditional concrete technology.

GRC is Versatile

Glass Reinforced Concrete (GRC) offers an unrivalled creativity and versatility in the development of new product designs because it can be used to accurately reproduce almost any small or large product design. In addition, end products can be finished in a wide variety of textures and colours.

Use of GRC in Precast GRC Planters

In their most basic sense, precast concrete planters are simply planters 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 much harder, stronger, more waterproof and durable. All of which are essential elements in meeting the architectural, engineering and construction standards required for the concrete planter boxes, troughs and pots used in commercial landscaping projects.

GRC technology can be applied in two ways in making precast concrete planters: a) By spraying a specialised concrete slurry mix into a mould using a spray gun that also chops and blends glass fibre reinforcement into the slurry during the spraying process; b) By adding chopped glass fibres into a specialised premix concrete slurring before pouring or pumping it into a mould.

Although GRC technology is an excellent material for the manufacture of very high-quality concrete planters, 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. Therefore, care should always be taken when sourcing GRC based precast concrete planters to ensure that the manufacturer is credible.

Precast GRC Planter Advantages

Precast concrete planters have the following significant advantages over the use blockwork or on-site formwork concrete planters: -

a.       Controlled environment – better quality control

Precast concrete products can be manufactured off-site in a controlled environment where temperature, humidity, air flow and adherence to production standards can be carefully controlled which are important factors in the production of high quality concrete products.

b.      Offsite manufacture – more efficient construction site

Precasting concrete products in an offsite location avoids clutter and disruption to a construction site when space is an issue.

c.       Independence from slab – avoids stress fractures

The very nature of blockwork and formwork concrete planters makes them an integrated part of a construction site which includes susceptibility to the associated stresses that can lead to cracking and water leakage. The modular nature of precast concrete planters means they are a stand-alone item and hence unaffected by any stress fracturing of the surrounding structures.

d.      Lighter than blockwork – suitable for balconies

Since GRC is very strong, the walls on the planters can be made very thin and light compared to blockwork or formwork. Light weight can be a significant advantage in circumstances where they are being placed on a balcony with weight restrictions.

e.      Thinner walls – more internal planting space

Another advantage of the thinner walls of GRC precast planters is that they allow for more planting space within the planters compared to blockwork and formwork without increasing the outside dimensions of the planter.

f.      Ease of replacement – flexible options

Since precast concrete planters are modular they can be replaced or moved relatively easily during future refurbishments or if a planter is damaged.