Microsilica applications: Tall buildings
Due to modified fresh concrete properties – less separation and segregation, increased cohesion, reduced viscosity – microsilica concrete ranging from ultra-high strength to lightweight can be easily pumped.
The minute spherical microsilica particles act as ball bearings and lubricate the mix eliminating blockage and wear as well as reducing concrete pump pressure.
311 South Wacker Drive, USA
One of the world's tallest reinforced concrete buildings is in Chicago, Illinois. At 293 metres high, with 70 floors, it changed the Chicago skyline. Elkem Microsilica concrete at 83 MPa was specified in the major columns, which meant a savings of steel reinforcement and concrete volume. Kuala Lumpur City Centre, MalaysiaThe tallest buildings in the world, the two towers are 450 metre high. The buildings were constructed with a reinforced concrete core and columns. The average concrete strength after 28 days was above 100 MPa. The mix design included 520 kg/m3 of cement and 30 kg/m3 of microsilica. This was the first application of Grade 80 concrete in Malaysia.
Baynunah Tower, Abu Dhabi
On its completion in 1995, the 156 metre high Baynunah Tower was the tallest building in the Arabian Gulf. The Gulf region poses a very harsh environment for concrete structures, especially in coastal areas. High ambient temperatures and sulfate and/or chloride contaminated soil can cause deterioration of concrete and corrosion of reinforcing steel so rapid that in some cases buildings less than 10 years old have been demolished. This means that very strict requirements to the quality of concrete constructions are required. For Baynunah Tower, Elkem Microsilica concrete was selected by the consulting engineers as the best overall concrete protection system due to its high strength, low water penetration and low chloride permeability.
BfG Bank Building, Frankfurt am Main
This was the first use of high strength concrete in Germany. Built in 1990, it is 186 metre high and consists of 47 stories plus 4 underground levels. The average concrete strength after 56 days was 112 MPa. The mix design included 450 kg/m3 of cement and 35 kg/m3 of microsilica.