Fibre Reinforced Facade Encyclopedia: Materials
Ultra high performance concrete is a cementitious composite with a very low water to binder ratio, an optimised particle packing, no coarse aggregate and a high dosage of steel or synthetic fibre, reaching compressive strengths above 120 MPa and retaining tensile capacity after cracking. The combination of strength, ductility and an extremely dense matrix allows structural elements a fraction of the thickness of ordinary reinforced concrete, and facade panels thin enough to be handled like a cladding sheet.
A 30 mm UHPC facade panel weighs about 75 kilograms per square metre and can span between supports without steel bars. A conventional reinforced concrete panel doing the same job is 100 to 150 mm thick because it has to cover steel reinforcement.
At a glance
| Property | Typical value | Note |
|---|---|---|
| Compressive strength | 120 to 200 MPa | Against 32 to 50 MPa for structural concrete |
| Flexural strength | 15 to 40 MPa | Fibre dosage and orientation dependent |
| Direct tensile strength | 7 to 11 MPa | Sustained after first crack, unlike plain concrete |
| Elastic modulus | 40 to 55 GPa | Higher than normal concrete; deflection rarely governs |
| Water to binder ratio | 0.16 to 0.22 | Requires high range water reducing admixture |
| Fibre content | 2 to 6% by volume | Steel microfibre 13 to 20 mm, or synthetic |
| Density | 2,400 to 2,600 kg/m³ | Denser than normal concrete |
| Facade panel thickness | 20 to 40 mm | Ribbed or folded for stiffness |
| Panel weight | 60 to 110 kg/m² | Including ribs, at 25 to 40 mm |
| Chloride ion penetration | Very low | Dense matrix; long design life in aggressive exposure |
What makes it ultra high performance
Four things, applied together. Particle packing is optimised so that every void between larger particles is filled by a smaller one, from fine sand down through cement to silica fume and quartz flour, leaving very little porosity. Coarse aggregate is removed, which eliminates the weak interfacial transition zone that limits ordinary concrete. The water to binder ratio is driven down to around 0.2 using polycarboxylate superplasticisers. And fibre is added at two to six percent by volume to carry tension across cracks.
The result is a matrix with almost no connected capillary porosity. That is what produces both the strength and the durability: chloride and carbon dioxide have very little pathway into the section, so cover requirements that dictate the thickness of conventional concrete no longer apply in the same way.
Production and curing
UHPC demands more of a plant than ordinary concrete. Mixing takes longer and needs higher shear energy, batching tolerances on water and admixture are tight, and the mix is sensitive to aggregate moisture. Autogenous shrinkage is significant because there is so little free water, so restrained shrinkage cracking has to be managed by mix design and by curing rather than ignored.
Many producers apply heat curing, commonly around 90 °C in steam for 48 hours, which accelerates strength gain, largely eliminates subsequent shrinkage and creep, and is why a heat cured element can be released to site quickly. Ambient cured UHPC reaches similar strength more slowly and continues to shrink for longer. The curing regime is part of the specification, not a factory preference.
Facade and architectural use
In facades UHPC is used for thin self-supporting panels, deep perforated screens and brise soleil, long spanning fins, stair treads, balustrade and planter elements, and complex mould formed shapes where the strength allows a very slender profile. Panels are typically 20 to 40 mm with integral ribs, sometimes with a light steel frame behind for large units. Finishes come off the mould in the same way as any cementitious material: off-form, acid etched, sandblasted, polished and integrally coloured.
The practical limits are cost, which is several times that of ordinary concrete per cubic metre, mould cost and production rate, which suit repetition rather than one-off geometry, and the tight tolerance band of the mix itself. Where steel microfibre is used, fibres at the surface can rust and stain, so faces are usually treated or a stainless or synthetic fibre is specified at the visible layer.
Fire
UHPC is a cementitious material with no polymer matrix, so a specific product can be tested to AS 1530.1, EN ISO 1182 or ASTM E136 and classified as non-combustible. As with any material, the classification belongs to the tested product, not to the category.
How it sits against other cementitious panels
Against conventional precast concrete, UHPC offers several times the strength and a much thinner section, at a higher material cost and with tighter production control. Against glass fibre reinforced concrete, the differences are structural rather than cosmetic: UHPC has a higher elastic modulus and real compressive and tensile design capacity, so it can be used for structural elements, while GRC is a thinner, lighter, sprayed or cast skin of 10 to 20 mm at 30 to 50 kilograms per square metre, generally not used structurally.
Both are cementitious, both can be tested non-combustible, and both take their finish from the mould. UHPC is heavier and stronger; GRC is lighter and more forgiving of complex one-off geometry. The GFRC versus precast and glass fibre reinforced concrete entries cover the comparison from the other direction.
Standards and references
- NF P18-470 and NF P18-710 (French UHPC material and design standards, the most complete code basis)
- AFGC Ultra High Performance Fibre-Reinforced Concretes recommendations
- ASTM C1856 Standard Practice for Fabricating and Testing Specimens of Ultra-High Performance Concrete
- SIA 2052 Ultra-High Performance Fibre Reinforced Cement-based composites
- EN 14651 residual flexural tensile strength; fib Model Code 2010
- AS 3600 Concrete structures; AS 1530.1 combustibility; AS 1530.4 fire resistance
Related terms
Questions specifiers ask
What compressive strength defines UHPC?
Most definitions set the threshold at 120 to 150 MPa, with 150 MPa common in codified practice. Strength alone is not sufficient: UHPC also requires fibre reinforcement and sustained post-crack tensile capacity.
Does UHPC need steel reinforcement?
Often not in thin elements, because the fibre carries tension and there is no cover requirement driven by corrosion. Larger structural members still use bars or prestressing, with the fibre providing shear and crack control.
Is UHPC non-combustible?
A specific UHPC product can be tested to AS 1530.1, EN ISO 1182 or ASTM E136 and classified as non-combustible, since the matrix is cementitious. Fire resistance is a separate question, and dense mixes need polypropylene microfibre to control explosive spalling.
How thin can a UHPC facade panel be?
Twenty to forty millimetres is the usual range for a panel with integral ribs. Below that, handling and mould filling become the constraint rather than strength.
How does UHPC compare with GRC?
UHPC is stronger, stiffer and can be structural, at 60 to 110 kilograms per square metre. GRC is a 10 to 20 mm skin at 30 to 50 kilograms per square metre, lighter and better suited to one-off moulded geometry. Both are cementitious and both can be tested non-combustible.
Comparing thin section cementitious options for a facade? ShapeShell-RC is our GRC system, Not Deemed Combustible under AS/NZS 1530.1 as tested by Ignis Labs. See ShapeShell-RC specifications
Reviewed by Richard Halvorsen, General Manager, ShapeShift Technologies. Last updated September 2026.