Ultra-high-performance concrete (UHPC) has six to eight times the compressive strength of traditional concrete. It is produced from a mixture of Portland cement, crushed quartz, sand, silica fume, super -plasticiser, fibres and water with no aggregates larger than one millimetre. Wollastonite (calcium silicate) filler may also be included in the mix. The fibres most frequently used are either high-strength steel for maximum strength or polypropylene (PP) of approx – imately 12 mm in length for lower load applications.A low water/cement ratio between 0.2 and 0.26 is used. The concrete may be cast into traditional moulds by gravity or pumped or even injection cast under pressure. When cast into traditional moulds, the mater – ial is self-leveling, so only slight external vibration of the formwork may be required to ensure complete filling. The material is designed for use without steel reinforcement bars.
Structural components in ultra-high-performance concrete may, after setting, be subjected to steam treatment for 48 hours at 90°C. This enhances dura -bility and mechanical properties, eliminates shrinkage and reduces creep. The material does not spall under fire test conditions
The enhanced compressive and flexural strengths of ductile fibre -reinforced ultra-high-performance concrete enable lighter and thinner sections to be used for structural components such as shell roofs and bridges, creating an enhanced sleek aesthetic. A high quality durable surface is produced from appropriate moulds (e.g. steel) coated with proprietary release agent.