Millennium Point is a ú113M landmark project in Birmingham, UK designed by architect Nicholas Grimshaw & Partners, and is part of a regeneration programme for the inner city area.
The tender scheme for Millennium Point said that it should reflect the city's industrial heritage. The design included the use of 400 exposed steel columns that would be visible throughout the four-storey building.
These columns were to be filled with concrete, but the complex and congested reinforcement arrangement in the tubes made conventional, vibrated concrete impractical.
Consultant Mott MacDonald was asked to come up with a solution. Selfcompacting concrete (SCC) was put forward as a way to minimise the risk of segregation around congested reinforcement and reduce the concrete placing times. A C60 SCC mix, with a slump flow of 600mm-650mm was specified and site trials were undertaken on columns. These trials were very successful and placing of SCC in the structure began shortly afterwards.
SCC, in its fresh state, has extreme flowability, but maintains stability, allowing it to self-compact under its own weight, thereby removing the need for mechanical vibration. Other benefits are reduced labour and plant requirements, shorter concrete placement times and improved compaction in areas of congested reinforcement. It also has the potential to enhance durability through improved compaction of cover concrete, and offers expanded buildability, eg concreting deep elements in single lifts. The lack of vibration brings environmental and health and safety benefits.
SCC was developed by the Japanese in the early 1990s and has been used in several projects in Europe, but Millennium Point represents one of its first significant applications in the UK.