Report on High-Strength Concrete

Description

The use and definition of high-strength concrete (HSC)has seen a gradual and continuous development over manyyears. In the 1950s, concrete with a compressive strength of5000 psi (34 MPa) was considered high strength. In the1960s, concrete with compressive strengths of 6000 and7500 psi (41 and 52 MPa) were produced commercially. In theearly 1970s, 9000 psi (62 MPa) concrete was produced.

Today, compressive strengths approaching 20,000 psi(138 MPa) have been used in cast-in-place buildings.Laboratory researchers using special materials and processeshave achieved “concretes” with compressive strengths inexcess of 116,000 psi (800 MPa) (Schmidt and Fehling 2004).As materials technology and production processes evolve, it islikely the maximum compressive strength of concrete willcontinue to increase and HSC will be used in more applications.Demand for and use of HSC for tall buildings began in the1970s, primarily in the U.S.A. Water Tower Place inChicago, IL, which was completed in 1976 with a height of859 ft (260 m) and used 9000 psi (62 MPa) specifiedcompressive strength concrete in the columns and shearwalls.

The 311 South Wacker building in Chicago,completed in 1990 with a height of 961 ft (293 m), used12,000 psi (83 MPa) specified compressive strength concretefor the columns. In their time, both buildings held the recordfor the world’s tallest concrete building. Two Union Squarein Seattle, WA, completed in 1989, holds the record for thehighest specified compressive strength concrete used in abuilding at 19,000 psi (131 MPa).High-strength concrete is widely available throughout theworld, and its use continues to spread, particularly in the FarEast and Middle East.

All of the tallest buildings constructedin the past 10 years have some structural contribution fromHSC in vertical column and wall elements. The world’stallest building, at 1670 ft (509 m), is Taipei 101 in Taiwan,completed in 2004. The structural system uses a mix of steeland concrete elements, with specified concrete compressivestrengths up to 10,000 psi (69 MPa) in composite columns.Petronas Towers 1 and 2, completed in 1998 in KualaLumpur, Malaysia, used concrete with specified cubestrengths up to 11,600 psi (80 MPa) in columns and shearwalls. At the time of this report, these towers are the secondand third tallest buildings in the world, both at 1483 ft (452 m).