What is GFRC? Composition, properties and how it’s made
A practical, numbers-first guide to glass fibre reinforced concrete for architects, structural consultants and builders who need to specify it or check a supplier.
GFRC (glass fibre reinforced concrete) is a cement-based composite made of cement, fine sand, water, admixtures and alkali-resistant (AR) glass fibres. The fibres replace steel reinforcement, so GFRC can be cast in thin sections, typically 10–40 mm, giving panels, jali, cladding and ornaments that are strong in bending but far lighter than precast concrete. It is also called GRC.
What GFRC is made of
GFRC is closer to a fibre-reinforced mortar than to ordinary concrete: there is no gravel, and the fibre does the job steel does in RCC. A typical batch at our workshop looks like this:
| Component | Spray GRC | Premix GRC |
|---|---|---|
| Cement (OPC 53) | 50 kg | 50 kg |
| Fine silica sand | 50 kg | 50 kg |
| AR glass fibre | 4.5–5% by weight | 2–3.5% by weight |
| Superplasticiser | 0.5 kg | 0.5 kg |
| Acrylic polymer | 5 kg | 5 kg |
| Water | 13.5 litres | 14.5 litres |
Two points matter more than the exact quantities:
- The fibre must be AR glass. Cement paste is strongly alkaline (pH above 12), and alkali slowly attacks ordinary E-glass. AR fibre contains roughly 16% or more zirconia, which slows that attack dramatically. Cheap “GRC” made with non-AR fibre is a common reason for panels cracking a few years after installation.
- The water–cement ratio is low, about 0.3. A superplasticiser keeps the mix workable without extra water, which keeps the matrix dense and strong.
A short history
People tried reinforcing cement with ordinary glass fibre in the mid-20th century, but the fibres lost strength in the alkaline matrix. The breakthrough came from the UK’s Building Research Establishment, where Dr A. J. Majumdar’s team developed a zirconia-based alkali-resistant glass in the late 1960s. Pilkington commercialised it as Cem-FIL in the early 1970s, and the industry body, the Glassfibre Reinforced Concrete Association, followed in the mid-1970s. Since then GFRC has been used worldwide for façades, ornaments and architectural screens. In India it has become the standard material for jali and decorative elevation work.
Spray vs premix: the two ways to make GFRC
| Spray (spray-up) | Premix (cast) | |
|---|---|---|
| How | Slurry and chopped fibre (about 25–40 mm long) sprayed together into the mould, layer by layer, then roller-compacted | Short fibres (about 12 mm) mixed into the mortar, then poured or vibrated into the mould |
| Fibre content | About 4.5–5% by weight | About 2–3.5% by weight |
| Strength | Higher flexural strength | Lower, but enough for small and solid pieces |
| Best for | Façade panels, large jali, cladding, domes | Balusters, capitals, brackets, small ornaments, sculptures |
Most jali and façade work is sprayed. Premix is used where shape and detail matter more than bending strength.
Mechanical properties
These are typical 28-day values for well-made GFRC. Always ask your supplier for their own test results.
| Property | Unit | Spray GRC | Premix GRC |
|---|---|---|---|
| Flexural strength (MOR) | MPa | 20–30 | 10–14 |
| Limit of proportionality (LOP) | MPa | 7–11 | 5–8 |
| Compressive strength | MPa | 50–80 | 40–60 |
| Interlaminar shear | MPa | 3–5 | — |
| In-plane shear | MPa | 8–11 | 4–7 |
| Impact strength | kJ/m² | 10–25 | 10–15 |
| Elastic modulus | GPa | 10–20 | 10–20 |
| Strain to failure | % | 0.6–1.2 | 0.1–0.2 |
| Dry density | t/m³ | 1.9–2.1 | 1.8–2.0 |
How to read the table:
- MOR (modulus of rupture) is the ultimate bending strength. LOP (limit of proportionality) is the stress at which the material first cracks. Design is normally based on LOP and on the long-term (aged) strength, not the fresh MOR.
- GFRC’s strength reduces with age, especially the strain capacity, as the fibre–cement interface densifies over time. Specifications from bodies like the GRCA and PCI allow for this with design stresses well below fresh test values. This is normal and is why thickness should come from a calculation, not habit.
- Density is about 2 t/m³, close to normal concrete. GFRC is light because it is thin, not because the material itself is light. A solid 35 mm panel weighs about 70 kg/m², and a jali with open areas weighs proportionally less.
How GFRC elements are made
- Pattern and mould: a master pattern is carved, CNC-cut or 3D-modelled from the drawing, and a rubber, FRP or timber mould is taken from it.
- Mist coat (optional): a thin fibre-free face coat picks up fine detail and gives a smooth finish.
- Spray or cast: backing layers of fibre-reinforced mix are sprayed and rolled to full thickness, or premix is poured.
- Inserts and frames: stainless-steel sockets, anchors or a steel stud frame are embedded or bonded on for fixing.
- Curing: covered overnight, demoulded, then kept moist for about 7 days, or cured with a polymer-modified mix.
- Finishing and QC: edges dressed, dimensions checked, and test boards cut and broken to confirm strength and fibre content.
Our page on how GRC jali is made walks through the process with photos.
Where GFRC is used
- Façades: cladding panels, window surrounds, fins and screens.
- Jali: elevation screens, shaft jali, boundary walls and partitions.
- Classical elements: columns, capitals, cornices, arches and balusters.
- Roofs and interiors: domes, ceiling features, sculptures and planters.
Limitations to plan for
- It is non-structural. GFRC carries its own weight and wind load, not floors or walls. Fixings and the supporting structure must be designed for it.
- Thin sections need movement joints. GFRC shrinks and expands with moisture. Large panels must be free to move; locking them rigidly at every edge causes cracking.
- Quality varies widely. Mix, fibre and curing make the difference between a panel that lasts decades and one that crazes in two monsoons. Ask for the fibre brand, method and test results.
- Surface needs protecting outdoors. A breathable sealer or exterior paint keeps the colour even and reduces dirt pick-up.
Standards and specifications
India has no dedicated GFRC product standard, so projects normally refer to international documents:
- GRCA specification (UK): manufacture, curing and testing of GRC, including the regular test-board regime.
- PCI 128 (USA): specification for GFRC panels, mainly sprayed cladding on steel frames.
- BS EN 15422: specification of glass fibres for reinforcing mortar and concrete.
- EN 1170 series: test methods for GRC, including bending tests and dry density.
Frequently asked questions
What does GFRC stand for?
Glass Fibre Reinforced Concrete. It is the same material as GRC (glass reinforced concrete). See GFRC vs GRC.
Is GFRC stronger than regular concrete?
In bending and impact, yes, by a wide margin for the same thickness. That is why it can be so thin. It is not used as a structural material in place of RCC, though.
How long does GFRC last?
Made with AR glass fibre and properly cured and fixed, GFRC elements perform for decades outdoors. Early failures usually come from the wrong fibre, poor curing or rigid fixing, not from the material itself.
How thick is GFRC?
Typically 10–15 mm for sprayed skins on a steel frame, and 25–40 mm for self-supporting jali and panels. The right thickness depends on the panel size, height and wind exposure.
Is GFRC fireproof?
GFRC is non-combustible because it is made of cement, sand and glass. It does not burn or add fuel to a fire.
About the author
Written by the people who draw, mould, cast and install GRC at Asian GRC, a Gurugram manufacturer working in glass fibre reinforced concrete since 2012. Our work includes GRC jali for Taj Palace, New Delhi (G20 Summit 2023) and for power projects of NTPC and NPCIL. Figures in our articles come from our own production and site work, or from the standards and sources we cite.
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