It towers over the city in high-rises, paves the Chicago Riverwalk and reflects thunderous cheers at Wrigley Field.
Concrete is everywhere in Chicago, and its key ingredient doesn't have to travel far to get here.
For much of the limestone used to build Chicago's buildings, fix its roads and even renovate Wrigley, the journey starts in a mine deep below the Earth's surface near Joliet.
"It's hard to believe," said Aaron Ozinga, president of Ozinga Materials & Logistics, an Ozinga company. "(That stone starts in an) underground quarry in Joliet and there it is standing tall in Chicago."
Ozinga supplies building materials to many of the contractors that are helping reshape Chicago's skyline, these days mainly with residential high-rises, such as the 67-story mixed apartment and condo tower One Bennett Park near Navy Pier.
Construction materials are heavy and can be expensive to ship far, so they often stay local. Mokena-based Ozinga gets much of the limestone that flows into Chicago construction from LafargeHolcim, the Zurich-based building materials giant that operates the Joliet mine.
Number of construction cranes operating in Chicago
SOURCE: Rider Levett Bucknall
Nowadays, business is good for the concrete-focused companies, at least downtown. In December, there were 56 cranes in the sky in Chicago, according to Rider Levett Bucknall, a construction consultancy with Phoenix-based North American operations. Construction like this hasn't been seen in the city for nearly 10 years, Aaron Ozinga said -- since before the recession.
"There was nothing going on, nobody building anything," he said. "Everything pretty much came to a halt, but now things are obviously picking back up."
Outside of residential high-rises, Ozinga recently has shipped concrete, containing material from LafargeHolcim's Joliet mine, to projects including the renovations at Wrigley Field, the last phase of the Chicago Riverwalk, and the construction underway on the Stevenson Expressway and Lake Shore Drive interchange near McCormick Place.
Downtown Chicago marks some of the best growth that's happening in the region, said Matt Dantinne, head of the Mid-America region for LafargeHolcim's aggregates and construction materials business.
"When the economy turned off, the spigot turned off. Housing completely stopped in the Chicago area," Dantinne said. "We're back to a much better balance right now."
That means going deeper into the mine.
The steps of the process
Much of the construction material used to build Chicago’s skyscrapers or renovate Wrigley Field comes from local mines and quarries. Here’s the route the limestone takes from an underground mine near Joliet to a downtown high-rise.
and Ship Canal
Des Plaines River
Into the mine
At about 300 feet below ground, the mine is dark and dusty. Employees work in clouds of light to break down the limestone, drilling holes in the walls, stuffing them with powder and blasting them out. There are about 20 LafargeHolcim employees that work primarily in the mine, which stays at about 55 to 60 degrees year-round. Every day, about 12,000 tons of rock is removed from the mine, and it's run through a crusher before it ever surfaces. There's one roadway into and out of the mine, and hanging over the exit and entrance ramp is a conveyor belt that carries out the broken-up limestone.
Back on the surface
The chunks of stone that emerge from the mine are no larger than about 6 inches in diameter, but above ground they must be broken down further. The recipes LafargeHolcim's clients use to make their products call for different sizes of material, from sand to stone and everything between. "All we're doing here is crushing it to get it ready for the different recipes," Dantinne said.
By the river
The material from the mine is trucked to a nearby port on the Des Plaines River, where it's loaded into Ozinga's barges and shipped into the city via the Chicago Sanitary and Ship Canal to the Chicago River. Each barge holds 1,550 tons of material, or the equivalent of 70 truckloads.
The barges arrive
Ozinga has two concrete plants in the city that sit on the Chicago River: one just north of Goose Island and the other near Chinatown. The material comes off the barges and is mixed together. Aaron Ozinga explained the difference between cement and concrete: "Cement is like flour in a cake. It's an ingredient ... used to bind all of the aggregates together. Concrete is the hard-formed stuff."
On the job
Once water comes in contact with cement, the cement truck must be unloaded in 60 to 90 minutes. Ozinga's red-and-white-striped trucks deliver the concrete in 9-cubic-yard loads, said Paul Ozinga, Aaron's brother and executive vice president at Ozinga Ready Mix Concrete, another Ozinga company. So if there's a 400-cubic-yard deck on a high-rise being poured, 44 truckloads of concrete would be delivered to the site. With a new truckload coming every five minutes or so, the pour could take hours.
Once poured, the concrete hardens, becoming a part of the skyline less than 50 miles from the ground in which its limestone was formed.