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This film was produced in 1965 by The Portland Cement Association of Skokie, Illinois. “Portland” is a type of cement. According to its web site, the PCA “represents cement companies in the United States and Canada. It conducts market development, engineering, research, education, and public affairs programs.”
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Groundbreaking was on November 22, 1960 on the site of the original Block 1 of the Chicago township, designated before Chicago became a city in 1837.
(Left) View from State Street bridge, looking northwest. The building in center frame with Dutch-influenced architecture is the current location of Harry Caray’s Italian Steakhouse.
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The term they are using in the film is “in-situ piling,” which means a tube (called a casing) – closed at the bottom with a plug – is driven into the ground to a required depth. Concrete is then poured into the tube, forming a “pile” inside the casing.
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Drilling went down 115 feet, passing through layers of fill, gravel, and a variety of clays. The maximum diameter of piles varied from 24 to 66 inches. Every 24 hours, four casings containing reinforcing bars were drilled to bedrock and filled with concrete, then capped with a heavy steel plate.
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There are three concentric rings of piles. The central core is constructed over the inner ring, but most of the load is taken by the outer rings.
The central core is 32 feet in diameter. Its concrete was cast at a rate of eight feet six inches per day. The thickness of the core walls decreases from 30 inches at the base to 12 inches at the top, 588 feet above the base.
(Left) View from over State Street bridge, looking down at uncompleted commercial block (left) and east residential tower (right) with exposed central core.
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Concrete was supplied by a “ready-mix” plant, which means the concrete is pre-mixed, then delivered to the work site. After 28 days, the concrete had a strength to withstand 7,000 pounds per square inch. A relatively lightweight concrete was used for beams (horizontal spans over an open space) and floors. Concrete of normal density was used for walls, (vertical) columns, and the main core.
Construction crews worked in a continuous 48-hour cycle. The same crews worked on both towers. The daily construction schedule appears to be...
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6 AM - Construction sequence starts. Carpenters began to strip the nine-foot-high wooden forms, external and internal, into which the concrete will be poured. The forms are divided into eight segments. Concrete arrives on a conveyer system at a maximum rate of 100 cubic yards per hour.
7 AM - A crane is raised and the external (outer) forms are reassembled, reinforcement bars are fixed into place, and openings in the core are boxed out.
Late morning - Half of a floor was finished and concreting starts on the second half.
12 PM - The internal (inner) forms are re-positioned. Surveyors set out for the next floor.
2:30 PM - Ready for concreting. Work begins on hoisting forms from three floors below, where they had been used four days earlier.
Late afternoon - Concreting is completed on the entire 12,000 square foot floor and carpenters are assembling the forms that will encase the concrete.
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The work cycle continued until the following morning. Steel fixers positioned and secured the reinforcing bars used to strengthen the concrete. Then electricians installed electrical conduit. They were followed by plumbers and sheet metal workers. By 2:30 p.m., a third gang of steel fixers began the final work of assembling and fixing reinforcement for floor slabs.
By 6:00 a.m. the following morning, 48 hours after construction began on the previous floor, casting started on the next floor.
For the ramps and columns on the parking levels, concrete forms made of glass fiber were used for a better finish. On the 16-story office block, glass fiber molds were used to cast the arches of the lower stories. The textured finish was achieved by spraying colored marble chippings onto a sand/cement rendering.
To create the strong lines on the south face of the office building, special “seal forms” were used to cast the mullions that frame the windows and support 50 percent of the building’s floor load.
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With major structural work completed, utilities and elevators installed, windows were glazed and interior finishing proceeded. Working five days a week, crews topped out the east tower 12 months after work started.
(Left) Man climbs television mast that added 437 feet to height of west tower
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