UHPC removes the traditional constraints of concrete, allowing the designer to conceive extremely thin elements, organic forms and complex geometries with mechanical strengths comparable to those of steel.
The UHPC revolution lies in grain-size optimisation pushed to the limit (packing density). Gravel and crushed stone are eliminated, using only fine quartz sands (max 1 mm) and silica fume, whose nanoparticles fill the microscopic voids between the cement grains. The water/cement ratio drops to extreme values (< 0.25), made manageable only thanks to massive doses of super-plasticising admixtures.
To overcome the intrinsic brittleness of such a rigid matrix, high-carbon steel or polymer (PVA) micro-fibres are dispersed in the mix. This volumetric addition (typically 2-3%) gives the material remarkable tensile strength and a ductile (strain-hardening) post-cracking behaviour, which often allows the traditional passive reinforcement to be eliminated entirely (rebars and stirrups).
Standards
European and international references applicable.
Physical properties
Usage environment
The absence of coarse aggregates allows replicating formwork texture at micrometric level. The aesthetic result is comparable to ceramics or marble — smooth and free of bug holes.