Advancements in concrete technologies where concrete was improved to a strength of up to 9,000 psi allowed this building to reach 76 stories, 859 feet high.

Tallest Reinforced Concrete Building Between 1975 and 1990

Concrete contractors have come a long way since the building of the Ingalls Building in 1904, and Chicago, Illinois has become a popular place to build concrete high rises. One reason for this is because the Windy City has a good supply of high quality fly ash, a concrete aggregate that allows contractors to produce a more workable concrete without adding more water. Water Tower Place in Chicago was the tallest reinforced concrete building in the world from 1975 to 1990, when it was surpassed in height by 311 South Wacker Drive, also in Chicago. Water Tower Place is 76 stories, 859 feet tall and contains concrete with a strength of up to 9,000 psi.

Named after the Chicago Water Tower, the building was designed by Loebl, Schlossman, Dart & Hackl. The general contractor was Inland-Robbins Co. and the concrete was supplied by Material Service Corporation. Contractors used both lightweight and normal weight concrete, as well as high strength concrete. A conventional design was used for the bottom 12 floors and a tubular design for the top 64 stories.

Without the development of high-strength concrete, Water Tower Place would not exist today. In the 1950s, any concrete with a compressive strength of 5,000 psi was considered high-strength. That definition changed in the 1960s, when high-strength concrete was anywhere between 6,000 and 7,500 psi. It wasn't until the early 1970s that concrete with a strength of 9,000 psi, the strength of some of the concrete used on Water Tower Place, was developed. Advancements in improving concrete's strength have continued to improve the material even beyond the time Water Tower Place was created. Today concrete can reach strengths approaching 20,000 psi.

Only some of the concrete in Water Tower Place is a strength of 9,000 psi. Concrete contractors used 11 different mixes, varying from 3,000 psi for the slabs to 9,000 psi for the columns. The structural system of the building consists of reinforced concrete on the outside with steel columns on the inside and steel slabs topped with composite concrete. At 2/3 the height of the tallest steel building when it was built, Water Tower Place serves as an example of how concrete's abilities make it a strong rival of steel.

Not only is the building composed of concrete, but concrete also lies underneath the building site. Construction was delayed unexpectedly for several weeks when concrete contractors discovered a stream running under the building site. Concrete saved the day-and millions of dollars. A giant concrete dome was used to plug the water so that construction could continue.