What is GRC?

Constituent materials

Glass Fibre reinforced concrete (GRC) is a composite material made up of various constituent materials including; Binders (cement, pozzolans), Aggregates (silica sands), Fibre (Alkali resistant glass fibre), Admixtures (e.g. plasticisers, polymers, titanium dioxide, oxides etc) and water.

production

GRC is typically made in one of two methods, either ‘spray-up’ or ‘premix’. The method selected is largely dependant on the product being made (e.g. large flat panels vs complex 3D forms respectively) with each having their own advantages for the desired performance characteristics. With premix the fibre is pre-cut, mixed with the other ingredients and then hand pressed or trowelled into a mould. With the continuous spray method a glass fibre ‘roving’ is fed into a compressed air spray gun, where the fibres are cut to length and mixed simultaneously with a sand/cement slurry. Both methods require careful hand compaction into the mould using a spring roller.

For both methods Liquidstone first lay down a fine ‘mist’ coat which has no fibre onto the mould and this forms the decorative or face layer. Using this technique achieves a superior quality finish and often times means no additional post-production is required e.g. repairs, fairing, filling, painting etc.

Moulds and formwork

Moulds can typically be made from a variety of materials such as MDF, Plywood, Steel, Fibreglass and Polyurethane rubber etc or a combination of one or all of these materials.

Careful consideration must be taken to select the most appropriate material or combination of materials for each mould or application e.g. a single use one-off product will likely have a mould made using low cost material such as MDF whereas a mass produced product may benefit from a more expensive mould made from fibreglass with a PUR rubber liner that can be used many 100’s of times.

Surface finishes and treatments

There are almost limitless possibilities for colour and texture that can be applied post-production

  • Off-form - smooth or textured surfaces, intricate patterns

  • Exposed / fine aggregate including ‘Graphic concrete’ and Sand-blasting

  • Mechanical abrasion - honing / polishing

  • Painting / Staining - a wide range of colours and effects are achievable

  • Hydrophobic coating and sealers