As a nation whose built environment revolves around the use of concrete, all of us in Mexico need to start brainstorming an alternative future. For example, how will the Mexico City of the future look if concrete is no longer the cheap and abundant resource it is currently.
To start, let’s sketch out the context for what cement is. Ordinary Portland Cement (OPC) was patented by Joseph Aspdin in 1911. OPC is a mineral ‘glue’ called clinker, composed mainly of lime and clay powder, fired at 2,000 degrees Celcius, a process which makes it highly reactive. A little gypsum also gets added. When the clinker is later combined with sand, gravel and water, we call the resulting mix ‘concrete’. The concrete dries, absorbing CO2 from the air (carbonating) into hardened artificial stone. If oil was the lifeblood of the Industrial Revolution, concrete became its bone and muscle. It has been shaped into the buildings, roads, bridges, skyscrapers and dams of modern society for 200 years.
The OPC formula has skyrocketed to become the second most utilized commodity on the planet, second to potable water. To make it more personal: about 4 tonnes of concrete are produced per person PER YEAR, worldwide. The number varies by country but, basically, that’s representing you and me.
So, what is it about this material that makes it a ticking time bomb of obsolescence? In my opinion, there are 3 reasons Portland Cement is facing a predicament of dinosaurian-proportions. Really 4, if you include the related, but unsexy, issue of usage rates.
- Clinker is in crisis
- Aggregate is in crisis
- Freshwater is in crisis
- Usage rates are soaring.
CLINKER. For every ton of clinker produced, almost an equal amount of CO2 is produced. Mercury emissions are also on par with coal-fired power plants. Bad, but what is less known, is that making 1 ton of cement requires about 1.5 to 2 tons of raw material (shale and limestone). This is simple math: if you spend 2 dollars to every dollar you earn, you are going to go broke! And Mother Nature doesn’t issue credit to the bankrupt.
- AGGREGATE. Put simply, we are running out of sand and gravel. As unbelievable as this sounds, the rates of sand and gravel being naturally renewed are being outrun by usage rates. With Portland Cement, only clean, non-salty sand is utilized, since salty sand corrodes internal metal reinforcement and weakens the lime component. So you can cross out the Sahara desert and the beach as aggregate sources. I’ve been noticing more and more financial columns bringing up this topic. Forget gold-backed money, there is now a sand-backed cryptocurrency called Sand Coin, a sign of the times.
- WATER. We tend to think of freshwater scarcity in terms of drinking water supplies, which is completely valid. We don’t think of freshwater supplies locked up in the crystalline structure of Ordinary Portland Cement. Freshwater is the key chemistry activator here: saline water introduces corrosion issues for metal reinforcement and weakens the lime content of the clinker. Did you know that each decade we lock up approximately 3,400 km3 of water in concrete, the volume equivalent to Lake Huron? To boot, excessive quantities of freshwater are used to clean out our fleets of concrete delivery trucks.
- USAGE RATES. With newfound awareness about the impacts of cement, let us consider the swelling usage rates of this high-impact commodity. These rates directly relate to population increases, rising middle classes around the world and global aging infrastructure. In China alone, the built environment constitutes 40 billion m2 (Kang 2014) and is expected to grow to 68.8 billion m2 by next year (Ji 2011). According to Ed Mazria of Architecture 2030, by 2034 ¾ of the infrastructure in the US needs to be re-built. As far as worldwide building stock, we will be ‘tearing down and rebuilding 900,000 billion ft2 within 2 to 3 decades- the equivalent of rebuilding New York City every 35 days’ (Autodesk). Once upon a time, in an age of unlimited resources, this growth was an unprecedented opportunity for the cement industry. Today, to live happily ever after, we need to be real about resource limits and revolutionize our built environment accordingly.
Luckily, the answers are already here. With political will, investment, and a healthy dose of humility, the Titanic can be re-directed. High mass timber systems, lightweight building envelopes, plant-resin based binders that can utilize cellulostic aggregates are among the suite of solutions. Ceramic-based coatings to protect metal like Eoncoat or alternative cement-free plasters like those of my own company, PHYTOSTONE, are fledgling efforts to build with new possibilities. In short, steering architecture towards light weight structures with skeletal support frameworks, advanced coatings and ‘carbon negativity’ as their imperative are crucial to future-proofing the built environment. We can evolve our materials and design in a resource-conscious direction. But it begins with planning for obsolescence and reimagining our future.