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Cement — the real mark of human civilization

July 20, 2014

pouring-concrete-cambie

The so-called concrete jungle may not be the nature of trees and streams and furry animals but it is very much the nature of people.

At the beginning of recorded human history there were cities with walls of plaster and cement. The stuff I watched some city workers make a sidewalk curb from a few weeks ago at Cambie Street and 10th Avenue has been a building block of human civilization for over 9,000 years.

Pound-for-pound, there’s nothing better than cement-based materials for building the cities needed to house the billions of people on earth but the worst thing is that the production of lime-based cement materials, including concrete, plasters, mortars and many kinds of bricks, is also a significant contributor of carbon dioxide, a greenhouse gas tied to global climate change.

For better or worse, though we’re probably stuck with the stuff. I believe we’ll wean ourselves off fossil fuels long before we can see our way to living without cement.

The softer side of cement

boot-mark

One small step…. In alley behind Shoppers at 13th Avenue and South Granville Street.

As a person born and raised in cities, it’s just possible that I love concrete the way some people love trees. I don’t exactly hug the sidewalks but I have been know to sleep on them so you should know that my relationship with concrete can get pretty intimate.

A playful side-effect of the stuff’s key property of working wet and drying rock hard are what you might call urban fossils — imprints made in wet cement and concrete — they’re all over the place in a city the size of Vancouver.

Some are deliberate, such as the official city date stamp on a sidewalk or  the neighbourhood kids’ initials on the same sidewalk, both made while the concrete was wet and setting.

When Sumerians let a typo slip through on clay tablet

Concrete proof of love. Would that it were always as enduring.

Other imprints are accidental — the boot prints of construction workers for example.

Then there are marks that are not accidental so much as incidental.

Concrete parkade and building walls all over the Vancouver are imprinted in exquisitely detailed wood grain patterns thanks to concrete’s amazing ability to the hold fine the detail of the original plywood forms.

I hope future archaeologists like woodgrain because they'll find it everywhere in our cities.

The Shopper’s on 13th. Future archaeologists will find wood grain everywhere.

The new Shopper’s Drug Mart building on South Granville Street at 13th Avenue is a rare concrete structure that selectively used wooden forms purely for decorative effect.

While most of the building was formed with smooth plates, rough wooden planks with very pronounced wood grain were used to form the wall beside the 13th Avenue entrance.

wood-mark-02

Good old cement

Plaster, mortar, stucco and cement are basically the same thing, a binder material, usually lime-based, that hardens to the consistency of stone. Concrete is cement extended with gravel. Asphalt is a type of concrete that binds gravel using bitumen, a by-product of petroleum, rather than cement.

Sophisticated use of lime plaster dates back over 9,000 years in the Near East. And those darned Egyptians were doing very fine work with plaster  some 4000 years ago.

sidewalk-mark

Oldest I’ve found. 1909 sidewalk date stamp at 10th Avenue and Columbia Street.

The first use of concrete dating back over 3,000 years ago was essentially an innovation of lime plaster. The Romans didn’t invent concrete as such. They invented hydraulic cement-based concrete which can set and harden underwater and their 2000-year-old recipe for hydraulic concrete is still superior to our modern concrete.

An inconvenient truth about cement

Here’s something many people don’t know about cement; it’s right up there with  fossil fuels as a major producer of the greenhouse gases which are contributing to global warming and climate change.

Cement production is arguably the fourth top contributor to greenhouse gas emissions, behind natural gas, coal and petroleum.

Cement production is estimated to be the third-largest source of greenhouse gas emissions in the United States, and responsible for 5 to 10 percent of global carbon dioxide production.

In British Columbia, cement production may account for something like 50 percent of industrial CO2 emissions, or 13% of the total CO2 emissions in Metro Vancouver — or may have seven years ago. The undated website listing these stats refers to the GVRD (Greater Vancouver Regional District), which became known as Metro Vancouver in 2007.

Most of the world’s concrete is made with Portland cement, the production of which requires an enormous amount of energy; the lime and clay mixture must be heated to over 1.371 degrees Celsius (2,500 degrees Fahrenheit).

The high temperatures allow cement kilns to burn to all manner of thing for fuel: natural gas, coal or, quite often, used tires.

Only some 40 percent of the CO2 gas emissions are accounted for by burning the fuel to heat the cement. At least 50% of the emissions are from the inherent chemical reaction. Basically all the carbon sequestered in the lime is released into the atmosphere as carbon dioxide.

On the one hand, Portland cement, is caustic, toxic, potentially carcinogenic and by its very nature releases a range of greenhouse gases. On the other hand it is cheap and, for the last 250 years has been an essential enabler of human civilization in general and for the West in particular.

Without the invention by the French of modern methods of reinforcing concrete combined with other techniques of building with steel (the production of which is another big CO2 producer) homelessness would be the rule in Western countries not the exception.

Even as I type, construction of North America’s tallest contemporary wood building continues. The Wood Innovation and Design Centre (WIDC) in Prince George, B.C., will top out at an astonishing 29.25 metres or a dizzying ten whole storeys.

I can imagine our civilization functioning without petroleum (not easily, I admit) but I personally find it almost impossible to imagine housing a human population of 7 billion without reinforced concrete buildings.

No “peak cement” on the horizon

The production and use of Portland cement has been steadily growing since the 1750s. Between 2006 and 2010 world production of Portland cement increased 26 percent.

In 2010 the world is estimated to have produced 3,310 million metric tons of hydraulic Portland cement with China producing as much as 56 percent of the total — 1,880 million metric tons.

China in turn consumed 58 percent of the world’s cement supply in 2010 and is expected to be an importer of vast amounts of cement for the foreseeable future.

Last year, China’s share of world cement production reached 57.5 percent.

No one talks about an impending shortage of cement, the constituent ingredients being as common as dirt.

No one is the boss of us

The tendency of the environmental movement to turn global warming into a single issue fight focusing on fossil fuels seems a bit narrow and wrong-headed to me.

Certainly our fossil fuel dependency is a huge source of greenhouse gases but it’s just one of many dependencies we have as a species. Each of them contributing its share to fouling our planet.

The fact is is that if it’s not one thing it’ll be another.

The real problem is us — our belief that we are the undisputed masters of the universe and we can do anything we want without fear of consequences and no one — not even ourselves apparently — can tell us what not to do.

Until we change that attitude we’ll just keep doing what we’ve always dome which is whatever we like.

To misquote William Shakespeare:

The fault, dear Brutus, is not in our cars, but in ourselves.

From → Worldwide

2 Comments
  1. m. subramanam permalink

    how print wood grain texture on concrete wall

    • The wall was made by pouring wet concrete into a plywood construction form. The wood grain pattern of the plywood naturally left its mark on the concrete.

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