Chemistry, Materials & Packaging
Why Sustainable Concrete Will Be the Bedrock for Future Megacities

The US’s infrastructure is falling apart beneath our feet. In 2017, the American Society of Civil Engineers (ASCE) gave our infrastructure a “D-” on its infrastructure report card. There are so many considerations for infrastructure repair, it’s mind-boggling. From aviation to wastewater systems to public parks, it all needs work. There are two common threads throughout: energy and concrete.

Energy plays the biggest role because you need energy to do repairs and to operate business as usual. You also need it to innovate. Increasingly, people are recognizing the value of renewable energy in this respect. Bounce Energy reports that investors are taking renewable energy seriously as a “key component of infrastructure investment.” In part, this is because companies such as JPMorgan Chase have committed to sourcing 100 percent of their energy from renewables by 2020.

The elephant in the room is concrete — it’s a huge part of the crumbling picture. Roads, ports, bridges, dams, levees, sewers — these are just a few of the structures that rely on concrete. Other structures, such as buildings, railroads and inland waterways, incorporate concrete in various integral ways.

Our system of commerce was built on a substance constantly in need of repairs. According to the University of Ohio, traffic increased by 39 percent between 1990 and 2009, and only 42 percent of our highways are operating at capacity. And the US is a landlord refusing to make repairs: Between 1990 and 2009, there was only a 4 percent increase in new road construction; ASCE gave our roads a D on the infrastructure report card.

As we’re wearing our infrastructure down, climate change is contributing to an increase in extreme weather events, including storms and floods. This graph from the National Climate Assessment shows the observed US trends in heavy precipitation:

The obvious solution is to focus on rebuilding concrete infrastructure with a focus on waterproofing and other sustainability measures. W.R. Meadows, a company that helps builders meet LEED standards, reports that, while conventional buildings generate 40 percent of emissions in cities, ‘green’ buildings cut down on emissions by 34 percent.

Making buildings out of concrete also cuts down on deforestation, as concrete waterproofing helps buildings meet LEED standards. In particular, concrete vapor barriers help maintain air quality inside buildings because they stop vapor that would otherwise make its way through water-damaged concrete and lead to mold, mildew and fungus.

One role for waterproofed concrete could be to channel rainwater to sites where it can be treated and reused as drinking water. But when it comes to the future of sustainable concrete, there’s another possibility — a future that looks more like the past.

Ancient Rome and Sustainable Concrete

For centuries, it was a mystery as to how ancient Roman piers, seawalls and other concrete structures such as the Pantheon are still standing strong. Then, in 2017, a study published in the journal American Mineralogist revealed the answer.

Ancient Roman concrete takes advantage of a rare chemical reaction called a pozzolanic reaction. The concrete is made from volcanic ash (the pozzolan), which is a substance rich in silica, combined with quicklime (calcium oxide). The pozzolanic chemical reaction causes the concrete to harden when it interacts with water — a process that continues strengthening the concrete even thousands of years after construction.


In Japan, award-winning architect Yasuhiro Yamashita followed Rome’s example to create his new micro home, R.Torso.C. At a tiny 710 square feet, the house is made of a new kind of concrete called shirasu — a recyclable form of concrete that consists of volcanic ash from southern Japan, mixed with calcium hydroxide. Like ancient Roman seawalls, R.Torso.C’s walls will harden with time as the concrete interacts with water vapor and rainwater. Architectural Digest identifies this design as an example of how we’ll build homes in the megacities of the future; R.Torso.C also won the 2017 Award for Overall Excellence from the American Concrete Institute.

One added bonus is that the concrete won’t break down over time, which will save on money and energy for repairs.

The Future of Cities

R.Torso.C is a prime model for buildings of the future not only because it’s made of recyclable, sustainable concrete — it’s also right-sized and designed to create the illusion of capaciousness. The size of the building is important: By 2050, an estimated 70 percent of the world’s population will live in cities. Right now, cities cover just 2 percent of the land but generate 70 percent of greenhouse gas emissions. Tomorrow’s megacities with tens of millions of people must be comprised of sustainable structures that take up minimal space.

Looking down on a future megacity, hopefully, you’ll literally see green: Rooftop plants help mitigate the “heat island” effect, which is caused by cement buildings and parking lots that absorb heat instead of reflecting it back into the air. Reflective coating and solar panels can help mitigate the heat island effect, as well. For buildings to take maximum advantage of space, plants will grow alongside solar panels.

LEED promotes a host of other great ideas for optimizing buildings, including reusing rainwater and wastewater, employing sustainable materials, maximizing use of natural lighting, incorporating smart thermostats and enhancing ventilation.

Regardless, in large cities, concrete will continue to play an integral role in foundations, streets and pretty much everything else. If that concrete isn’t sustainable like the stuff found in Rome and R.Torso.C, we’ll still spend a lot money and energy making continual repairs. For future megacities to last, sustainable concrete must be part of the mix.


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