Sand and Gravel

It ubiquitous, and in one form or another, it has been around for thousands of years. Concrete. When the Egyptians needed a binder to fill in the cracks and stabilize the giant cut stones for the pyramids, they used a combination of soil, water and straw. The ancient Romans experimented with “glue” mixtures, often containing animal parts, forming an early version of cement to hold sand and water together. They even developed different kinds of “cement” by altering the additives for differing kinds of construction needs. If you have ever visited Rome, from the Coliseum to the networks of aqueducts, you’ve seen their version of concrete at work. That many of these antiquities remain standing is a testament to their durability.

Yet when concrete is used for more than simply a stabilizing binder to hold stones in place, where the fundamental surfaces are themselves concrete, those structures have a vastly shorter lifetime. But concrete is everywhere today. In 1824, a Brit named Joseph Aspdin, invented the modern version of that fundamental concrete adhesive – Portland cement – that revolutionized the explosive growth of concrete to build the modern world, really accelerating in the twentieth century.   

Today, sand, water and rock are bound together in one version of another of Portland cement. “Portland cement, the basic ingredient of concrete, is a closely controlled chemical combination of calcium, silicon, aluminum, iron and small amounts of other ingredients to which gypsum is added in the final grinding process to regulate the setting time of the concrete.” ConcreteNetwork.com

We seem to be totally dependent on concrete; it literally defines our massive urbanization of the planet.  Journalist Vince Beiser, writing for the June 17^th Los Angeles, explains how much it has become a fundamental part of the modern world… and some of the not-so-nice consequences that result: “Concrete is essentially just sand and gravel glued together with cement. It is also by far the most widely used building material on Earth. We consume twice as much of it every year as steel, aluminum, plastic and wood combined. That’s because cities are exploding, especially in the developing world, as people leave the countryside for a shot at a better life in the metropolis. The number of urban dwellers is rising by about 65 million people annually, according to the United Nations Population Division. That’s the equivalent of adding eight New York Cities to the planet every single year.

“There’s no way cities could grow this fast without concrete. It’s an almost magically cheap, easy way to quickly create roads, bridges, dams and housing for huge numbers of people. An estimated 70% of the world’s population now lives in structures made at least partly out of concrete.

“Making all that concrete, however, takes a heavy toll on the atmosphere. The cement industry produces 5% to 10% of total carbon dioxide emissions worldwide, putting it behind only coal-fueled power plants and automobiles as a source of global warming gases.

“Concrete also soaks up the sun’s heat, and cities’ countless miles of warmed-up streets and sidewalks create a phenomenon known as urban heat islands. When combined with the heat from motor vehicle engines, paved areas can boost the temperature in some cities by as much as 19 degrees Fahrenheit, according to the California Environmental Protection Agency. That kind of heat also boosts the formation of air pollutants, especially ground-level ozone, better known as smog.

“The most frightening aspect of our dependence on concrete might be that the structures we build with it won’t last. The vast majority of them will need to be replaced — and relatively soon.

“We tend to assume concrete is as permanent as the stone it mimics. It isn’t. Concrete fails and fractures in dozens of ways. Heat, cold, chemicals, salt and moisture all attack that seemingly solid artificial rock, working to weaken and shatter it from within. You could say our cities are like castles made of sand, except that they almost literally are castles made of sand.

“Many of the world’s concrete structures are already slowly disintegrating. The most recent report on the nation’s infrastructure by the American Society of Civil Engineers declared that one-fifth of our highways and one-third of our urban roads are in “poor” condition. According to the Federal Highway Administration, nearly one-quarter of all the United States’ bridges are structurally deficient or functionally obsolete. Our dams are in similarly dismal shape.

“Worldwide, as much as 100 billion tons of poorly manufactured concrete structures — buildings, roads, bridges, dams, everything — may need to be replaced in the coming decades, at a collective cost of trillions of dollars.

“To make matters worse, we’re running out of one of concrete’s essential ingredients: sand… Our planet contains enormous amounts of sand, of course, but the usable type — found mostly in riverbeds, floodplains and beaches — is a finite resource like any other. (Desert sand, eroded by wind rather than water, is generally too round to use for construction.) Humans consume nearly 50 billion tons of sand and gravel every year, enough to blanket the entire state of California. Most of that is used to make concrete.

           

“Mining sand is its own colossal industry with its own litany of environmental devastations. In the United States, countless tons are dredged up every day in almost every state, from the San Francisco Bay to rural Florida. The most accessible sources are increasingly tapped out. A 2012 report by California’s Department of Conservation warns that the state has access to only about one-third of the sand and gravel it will require over the next 50 years.”

What are the answers? Our crumbling infrastructure is significantly just old concrete that has exhausted its useful life. It has to be fixed and expanded to meet the needs of a growing planet. But no one has really figured out how we can fix and build what we need to fix and build. It’s time to start thinking about our priorities and what we really can accomplish. And adjust our expectations accordingly.

I’m Peter Dekom, and sometimes the most complex issues are part of the most basic structures that we simply take for granted.