What is UHPC?
Ultra-High Performance Concrete (UHPC) is a cementitious material with extraordinary high mechanical performance and durability. Unlike ordinary concretes, UHPC can be used in a wide variety of sectors, replacing other materials (steel, plastic, wood, coatings…) to improve the performance and the lifespan of the components or structures.
UHPC, also known as UHPFRC (Ultra-High Performance Fiber-Reinforced Concrete) is a material that synergically centralizes the technologies of the three main special concretes (self-compactability, fiber-reinforcement and very high compressive strength). These properties are based on a mix design following clear rules:
- Minimum water/cement ratio, which is possible thanks to the optimization of the particle packing and to the use of the last technology of high range water reducing admixtures.
- Use of selected aggregates with a maximum diameter that generally does not exceed the 5 mm.
- High fiber content to provide a strain-hardening response under tension and a ductile failure under compression.
The resulting material is extremely compact, as does not have a net of communicated pores to multiply the lifespan of the UHPC elements. Corrosion under cracked state is also drastically reduced, as the size of the cracks under service due to the fibers is several times smaller than in ordinary concretes. Besides, the extremely high compressive strength and the quality of the aggregates makes of UHPC the king amongst the impact-resistant and wearing-resistant materials.
Obviously, UHPC is a more performant material than ordinary concretes, so to provide the same capacity the amount of material employed can be reduced between a 40% and a 75%. Besides of the clear environmental benefits of this reduction of resources used, this implies to have much lighter elements, which is key for many aspects. A lighter solution may reduce installation costs, facilitate reparations of old structures, minimize the buoyancy required in floating structures, add thinner protective layers to industrial elements, or reduce the transportation costs of the precast pieces produced. Finally, at the end of the long life of the UHPC component, the amount to be recycled will be less than for any other option with concrete.
The competitiveness of UHPC solutions in many industrial and engineering applications is obvious. However, these uses are not straightforward and require the support of an expert that knows how to exploit the performance of UHPC and how to design efficiently with it. RDC has proven this knowledge for almost a decade, launching to the market first world applications with this material in fields as aquaculture, renewable energy and industry. We are convinced that we can also support you to exploit all the potential of the UHPC benefits.
Being a small amount of the volume of UHPC, fibers represent approximately half of its cost. This gives an idea of the relevance of fibers in UHPC, which would be brittle and useless without them. Through a high bonding strength with the matrix, fibers provide the toughness required under tension and bending, and the capacity to avoid a sudden failure under high compressive stresses. The addition of certain fibers can even turn UHPC an excellent fire-resistant material. Through its functionalities, fibers allow the reduction or removal of the traditional rebars, increasing the level of industrialization of the product and reducing the needs of the increasingly scarce specialized workforce.
As you can see, fibers in UHPC matter. And they matter a lot. Thus, choosing the right type and amount of fibers in the UHPC mix design is key for the technical and economic viability the UHPC application. Some of the reasons are that:
- Fiber content, geometry and slenderness have a strong influence on the rheology during mixing and pouring, particularly due to the self-compactability of a well-designed UHPC.
- The type of fiber, pouring methods and geometry of the mold affect to the fiber orientation, which has a direct effect on the mechanical performance, crack width and crack spacing.
Besides of considering the mixing, the pouring and the mechanical performance of the final product, a well-balanced choice of the fiber requires to also consider its price, its sustainability, and its durability in the UHPC matrix.
Obviously, only a team with a wide experience designing and producing UHPC elements can consider all these variables to give reasonable answers.
Weight reduction of 40-75%
Compresive strength 3 to 5 times higther
Lifespan up to 4 times greater
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