UHPC - a material for many applications in onshore and offshore wind energy production

UHPCUltra High Performance Concrete has been used for many years in offshore wind

and onshore wind energy production.

We produce our UHPC No.10 for these applications. The new grades UHPC are currently being tested and will be available to the market later this year.

Monopile wind turbine designs are still the most widely used standard foundation design in many coastal areas. Jackets -, Gravity base -, Tripods - and Tri-piles systems are also used depending on requirements and needs.

UHPC grouting is used in all foundation techniques.

Monopiles

UHPC grouting material is used for the connection between monopile and transition pieces.

We estimate that more than 2000 monopiles worldwide have been installed with UHPC grouting and transitions pieces.

At the moment we are working on the 4th generation of grouting material. In addition to the technical improvements, the fulfillment of a wide variety of environmental requirements is the prime objective of the development.

Benefits of using UHPC grouting material for the transition piece

• Extremely high strength
• Very good fatigue properties
• Minimal shrinkage
• Extreme bond between UHPC grouting material and steel
• Fast setting development
• Very high inner cohesion
• No mixing with sea water
• Absolutly seawater resistant
• Very low hydration heat
• No corrosion

Tripile

A Tripile foundation consists of three steel piles driven into the seabed after which a three-legged transition piece structure is slid into the three piles. The overlaps between piles and transition piece are grouted with UHPC concrete.

The UHPC concrete connections evenly distribute the forces from the three-legged transition piece to the piles

Tripod

A Tripod support structure/foundation is secured in place by driving three piles into the seabed through a sleeve in each of the three corners.

UHPC concrete is pumped into the annuli between pile and sleeve to ensure a strong and durable connection.

Jacket

Jacket foundations are secured to the seabed by four piles placed in a sleeve in each corner and driven into the seabed. Jackets are generally considered to be better than monopiles for seabeds where the substrate is poor or deeper water. So here UHPC grouting can be used in the "transition piece" and in the lower foundation.

Gravity foundations

Are well suited for rocky sea beds. The complete foundation system can be manufactured on land and then pulled into position with a ship and then sunk. Depending on the design, the entire foundation piece can be made from UHPC. UHPC No.11 will be perfect for slip casting the entire foundation.

                                                       
After the use of UHPC grout in offshore wind energy generation, the experience gained in onshore wind energy production has also been exploited.

Steel Tower

So far, steel towers in cylindrical or conical segment construction have been the state of the art.

Depending on the required hub height, up to five segments were mounted on top of each other. With the new tower heights, the segment diameters are getting bigger and bigger and the road transport between production and the site is becoming an ever greater problem.

Concrete Tower

More and more, as an alternative to steel towers, concrete towers are also produced and assembled in cylindrical, conical or polygonal segments. A disadvantage compared to the steel towers is the high wall thickness, which makes larger foundations necessary

The advantage is

• Favorable vibration characteristics, which leads to reduced noise emissions.
• Long life expectancy
• An ideal solution for high tower high and large rotor diameter
• Transport cost savings due to possible on-site manufacture
• The use of special UHPC concrete grades can lead to slender constructions and thus rougher component weight.
• Lower component weight can also make the foundation dimensioning more favorable, which can lead to cost reduction. The material experiences in the offshore transitionpiece technology can also be of advantage when using UHPC grout in the imbed ring assembly (connection tower / foundation).
• Since UHPC concrete of high quality have virtually no pore formation, they are extremely resistant to corrosion.
• There are little or no maintenance costs.
• The individual segments can be transported more cheaply than is possible with the steel segments.
• On-site fabrication is the use of slipforming is another option including the use of local concrete raw materials for the production of high-quality UHPCs.
• Furthermore, it is possible to produce extremely exact segments with UHPC grout material, which requires no or very little post-processing of the segment abutment surfaces.
• Our UHPC materials reach at least 70% of their rated strength in less than 48 hours, which can lead to lower manufacturing costs for segment production and delivery times can be drastically reduced.

Hybrid towers

This type of tower construction is a combination of concrete (lower part) and steel construction (upper part). IT combines most of the advantages of steel tower and accentuated tower technology. Here, too, the use of UHPC can lead to additional benefits and savings in terms of material and financial resources.
A segment construction or on-site casting by slipforming are possible. This reduces the costs of transport and reduces the foundation geometries.