Next-generation concrete
UHPC — Ultra High Performance Concrete
The fibre-reinforced concrete revolution: compressive strengths of 100–200 MPa, extreme compactness, ductility and unprecedented freedom of form.
Definition
The concrete
of the 21st century
UHPC (Ultra High Performance Concrete) or UHPFRC (Ultra High Performance Fiber Reinforced Concrete) is the most advanced evolution of fibre-reinforced concretes. With minimum compressive strengths of 130 MPa and typical values of 150 MPa, it surpasses GRC in mechanical performance and compactness, opening a broader universe of structural and architectural applications.
UHPC is achieved through carefully studied formulations: very low water/cement ratio (maximum 0.25, typically 0.20), optimised aggregate grading, a reactive addition (silica fume, nanosilica or metakaolin) and a high fibre dosage. The result is a virtually impenetrable material with exceptional ductility. Its extreme compactness makes it resistant to the penetration of aggressive agents (CO₂, chloride ions, water), ensuring long-term durability and safety that conventional concretes cannot offer.
Unlike GRC — designed primarily for façades and non-structural elements — UHPC can deliver ultra-thin structural elements, bridges, footbridges, floor slabs and singular precast components of extreme geometric complexity.
Chapter 6 of the Compendium
The ingredients of UHPFRC
UHPC is not simply conventional concrete with more cement: it is a carefully designed formulation in which every ingredient plays a precise role.
The Fibres
The indispensable ingredient. Without fibres there is no UHPFRC. They may be metallic (stainless or carbon steel), AR glass or PVA. They provide the ductility that transforms the brittleness of cement into toughness.
The Reactive Addition
Silica fume (microsilica), fly ash or metakaolin. It reacts with the calcium hydroxide in the cement to densify the matrix and eliminate capillary pores. It is the key to compactness and impermeability.
The Cement
Grey or white Portland cement, in proportions far greater than those of conventional concrete.
Water and Superplasticiser
Very low water/cement ratio (0.17–0.25). The superplasticiser (latest-generation polycarboxylates) compensates for the loss of workability caused by the high proportion of fibres.
Particle Grading
Typical UHPFRC contains no coarse aggregate: only fine sand and ground quartz, selected to maximise particle packing. Optimal grading is an art that makes the difference between formulations.
Typical formulation
Silica fume: 6.3 % (∼20 % by cement wt.)
Sand 0–2 mm: 38.8 %
Ground quartz/limestone: 8.0 %
Water: 6.5 % (w/c ≤ 0.25)
Steel fibres: 6.3 % (∼155 kg/m³)
Superplasticiser HRWR: 1.6 %
UHPC performance
vs GRC vs conventional concrete
| Property | UHPFRC | GRC | Conv. concrete |
|---|---|---|---|
| Compressive strength | 100–200 MPa | 60–80 MPa | 25–40 MPa |
| Flexural-tensile strength | 15–25 MPa | 15–25 MPa | 3–5 MPa |
| Modulus of elasticity | 45–55 GPa | 45–55 GPa | 30–35 GPa |
| Water permeability | Virtually nil | Medium | Medium |
| Projected durability | 100–200 years | 50–80 years | 80–100 years |
Note: indicative values prior to accelerated ageing tests.
The differentiating factor
Ductility:
the breakthrough
Conventional concrete is brittle: when it cracks, it loses all its strength. UHPFRC is ductile: once the limit of proportionality (LOP) is exceeded, the fibres maintain cohesion and the element continues to resist without failing. Two types of ductility are distinguished:
Applications
Where UHPC is applied
UHPC can be applied both in-situ and as precast. The revolution is not only in strength, but also in formal and constructive possibilities.
In-situ
Direct on-site applications
The ready-mixed concrete sector can supply UHPC from the batching plant with appropriate quality controls.
- — Rehabilitation of bridge decks
- — Strengthening of existing structures
Precast
Singular precast elements
Mould technology makes it possible to materialise geometries of extreme complexity. The Magical Frame at Port Adriano (Mallorca), with its materialisation directed by Juan Carlos Bolaños, demonstrates the possibilities of precast UHPC for creating large-format sculptural-structural pieces.
- — Architectural façades
- — Various ultra-thin precast elements
- — Footbridges and pedestrian bridges
- — Street furniture in spectacular designs
- — Singular and sculptural-structural elements
Moulds and fixings
Manufacturing technology
Whatever the type of UHPC, mould technology is decisive. An effective method: fabricate a pattern (in CNC-machined polystyrene, timber or resin) and produce the mould from the pattern. The design of fixing systems is equally critical for load transfer to the structure.
GRC → UHPC
The path between materials
GRC and UHPC are more complementary than competing. GRC offers over 50 years of maturity, full freedom of form and a well-established manufacturing cost. UHPC delivers structural performance and extreme durability where standard GRC falls short. The authors of the Compendium are specialists in both.
Go deeper
9 chapters on GRC & UHPC
The Compendium GRC ● UHPC includes three chapters devoted entirely to UHPFRC: ingredients, typical formulation, performance, standards (AFGC, fib) and worldwide scenarios. With an example formulation and advanced technical bibliography.