Not only is the Great Pyramid of Giza still standing after 4,500 years (other Egyptian pyramids even longer), but for around 4,000 of those years, it was the tallest manmade structure on earth. Will the towering skyscrapers in the dessert of Dubai last so long?
While the Great Pyramid is built from six million tonnes of solid rock, Dubai’s 828-metre Burj Khalifa – the world’s current tallest building and six times the pyramid’s height – is built from just 110,000 tonnes of concrete (and 39,000 tonnes of steel). Strangely, early skyscrapers such as those that dot the New York skyline are sturdier than many of their newer peers. The Empire State Building, for example, though not even half the height of the Burj, weighs two-thirds as much – and such is its strength that when a US Airforce B-52 bomber accidentally crashed into it at 330km/h in 1945, the building closed for just a few days.
‘They don’t make them like they used to’ is a phrase uttered ad nauseum in the digital era, but it’s arguably as applicable to some architecture too.
That’s not to say that modern skyscrapers aren’t hardy. The Burj is built to withstand weather events which occur around once every two millennia (versus every 700 years for regular buildings), along with regular lightning strikes that carry more power than a nuclear reactor, and absorb a 7.0 magnitude earthquake (swaying for up to a stomach-churning 11 seconds). But still, it’s hard to imagine it still standing in the year 7000 to rival the pyramids’ lifespan (so far).
“In fact, the impressive age of the pyramid is no accident,” writes Zaria Gorvett for BBC Future. “The ancient Egyptians believed the afterlife would last forever and took great pains to ensure their tombs would too. Pyramid design evolved over thousands of years, as they experimented with the materials and architecture that would live up to their ambitions.”
Whether by luck or design the Ancients’ cement (including that of the later Greeks and Romans) appears to be longer lasting than the modern-day iteration which can start to crack after just a few decades. It’s been discovered that their cement’s mud, volcanic ash, limestone, and seawater react over time to form a glue that reverts back to its raw ingredients to make rock. So, the limestone blocks that built the pyramids were essentially glued together by more rock: the Egyptians basically built their very own mountains.
The Egyptians also understood their shortcomings when it came to the laws of physics, and over-engineered by building extra walls instead of columns, essentially making the pyramids even stronger than they needed to be. Similarly, early skyscrapers appear so sturdy because the industry was still in its infancy and engineers added extra reinforcement just in case.
But it’s not just wear and tear or the wrath of Mother Nature that can bring down buildings, it’s human choice, too. In their relatively brief 150-year or so history, a surprising number of skyscrapers have been felled. A study by the Council on Tall Buildings and Urban Habitat (CTBUH) of the 100 tallest buildings to be dismantled by their owners found their average lifespan to be just 42 years. Singapore’s 234-metre AXA Tower is currently being torn down to make way for a 305-metre skyscraper for tech firm Alibaba. That only opened in 1986.
“The biggest issue, even if everything goes well, is that it is just an enormous waste of resources,” CTBUH journal editor Daniel Safarik tells New Atlas. “Concrete cannot be recycled, and most of the tallest buildings in the world use concrete for their main structural system.”
Concrete, the world’s most commonly produced construction material, is made using cement which accounts for 8% of the world’s CO2 emissions. And that’s before considering the impact of carbon-intensive steel manufacturing.
“Cities are becoming megacities, with many tall buildings clustered together,” adds Safarik. “If we’re not planning these to have centuries-long lifespans, we’re going to have a problem in 20 years.”
So do such skyscrapers have the potential for such long lifespans? Structural engineer of the Burj Khalifa, Bill Baker, thinks so. Maybe. “The structural materials are good for pretty much ever,” he tells the BBC. “Yes, if they maintain them, and no if they don’t.”
