UHPC or Ultra-High Performance Concrete is an advanced class of concrete that offers new opportunities in construction.
One of the most notable difference between conventional concrete and UHPC is the compressive strength. UHPC has a compressive strength upward of 120 megapascal at 28 days, compared to range of 20-50 megapascal at 28 days for normal concrete. The high strength properties allow to design thin, complex shapes, curvatures and highly customized textures.
However the high compressive strength is not the only advantage of UHPC. The product has extremely high durability due to a dense structure. The dense structure reduces permeability and potential corrosion. It allows the use UHPC successfully for bridges, off-shore structures, marine anchors, seismic structures, oil and gas application and many others. It should be said Whitecube does not produce bridges – we aspire to enable users through the use of our Kingcrete by use of our Micro-Factories as well as the retail products we produce along with any tiles and wall panels.
The composition of UHPC differs significantly from the conventional concrete with three-phase material of cement aggregate and water. To achieve high strengths, a variety of other additives and additives is needed. In the development of ultra high-strength concretes, the focus is initially on the optimization of granulometry. The staggering of grain sizes and the addition of fine aggregates such as silica fume and fly ash, the cavities in the matrix can be selectively filled, resulting in a high structural density results. In another words all the smaller particles fill the gaps in the bigger structure of particles making it more tightly packed.
Even with normal concretes, the compressive strength can be achieved by reducing the water cement value. The high strengths of ultra-high-strength concretes are achieved by setting the water-cement value slightly below the theoretically necessary water-cement value for complete hydration. As a result, the proportion of ultrafine particles in the cement paste is increased and consequently the porosity of the cement paste is lowered.
By lowering the water cement value, the workability deteriorates. Therefore, in order to achieve a fluid substance, a new generation of superplasticizers are used in the production of ultra-high-strength concrete.
Fibres are usually used in High Performance Concrete with a purpose to increase bending strength and ductility.
In the 1980s, UHPC with compressive strength up to 510 megapascal was developed and produced under specific laboratory conditions. It could only be prepared in the laboratory with some special methods such as vacuum mixing and high temperature curing. Although very high compressive strength could be achieved, the preparation of UHPC was very difficult and energy-consuming at that time.
In the 1990s, reactive powder concrete was developed. RPC is composed of very fine powders (cement, sand, quartz powder and silica fume) with size less than 1 mm and of the high packing density due to the use of different inert or reactive mineral additions they were called “ReactivePowder”. The compressive strength of RPC ranges from 80 MPa to 200 MPa. It has to be noted that. In 1997, the world’s first RPC structure, the Sherbrooke Bridge in Canada, was built. It was the first time that RPC had been used for building a whole structure. However, at that time, because of the high material cost, the applications of RPC were still scarce. The heat curing and the milling of quartz sand were very energy consuming, so RPC didn’t spread wide.
From the 2000s, much progress has been made on the development of UHPC, because of the progress in cement and development of highly effective superplasticizers. UHPC can be prepared with normal temperature curing now. Because of that from the 2000s, many countries have started using UHPC. UHPC bridges have been built in France, Australia Netherlands, Spain, Canada, Germany, Austria, Japan and Korea. UHPC also has growing applications in maintenance and development of US highway infrastructures.
With the growing applications of UHPC, a wide range of different formulations are available and can be adjusted to meet the individual needs of increasing number of different applications.
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