A crucial step towards building the next tallest building on Earth is underway: Engineers on the Kingdom Tower, a proposed 3,280 foot tower in Jeddah, Saudi Arabia, are beginning tests to figure out how to pump wet concrete more than half a mile into the sky.
There are plenty of technical challenges involved with building a one-kilometer-high tower, including (but in no way limited to!) lackluster elevator tech and the sheer weight of a tower this tall. And we haven’t heard about Kingdom in months, which seemed to indicate that the economic demand just wasn’t there.
But this week, the developers of the tower announced that an outside consultant—Advanced Construction Technology Services—is starting tests on the materials needed to build the tower: half a million cubic meters of concrete and around 80,000 tons of steel.
There are all kinds of reasons why this is the first item on the engineering agenda. First of all, the tower’s foundation will be 200 feet deep—and it has to withstand the salt water of the nearby ocean. One of the major things ACTS will test is the strength of different high-performance concretes—the most essential piece of the puzzle, along with the steel itself.
Up top, things are more complicated: To pour each successive floor, crews will have to pump millions of tons of concrete through a thin, pressurized tube—generally about six inches wide—to be poured by crews above. And gravity, as you might expect, does not get along well with wet concrete.
A traditional concrete pump. Image: Wikimedia.
So after ACTS finishes testing the strength of the concrete mix that’ll be used in Jeddah, its engineers will move on to logistics like pumping—and it sounds like they’ll be looking closely at how the Burj Khalifa did it.
When the Burj was built, it set a record for highest concrete pumping. A Samsung-led engineering team was able to pump almost six million cubic feet of concrete through a single tube, thanks to high-tech pumps developed by the German company Putzmeister.
Image via LEGO/Putzmeister.
Throughout almost the entire project, workers could only pour new floors at night—the temperatures, in the day, made it impossible.
Of course, the big caveat to all of this is that the Kingdom Tower might not ever get built. But that doesn’t actually matter as much as you might expect. Proving that concrete can be poured at one kilometer is just the next step along a ladder that reaches far beyond that. As Dr. Sang Dae Kim, the director of the Council on Tall Buildings, put it to Construction Weekly, “in terms of practicalities, we don’t need to built at two kilometers—but someone with a lot of money might still want to do it.”