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Portland Cement vs. The Environment


The construction industry has a tendency to be on the complicated side of things. This is completely understandable when you consider the combination of manpower, materials, machinery and vast sums of money required to build anything from a single family home, to an office building or an airport. The months (sometimes years) of planning, forethought and preparation needed before anyone dons a hard hat is staggering, it’s hectic, maddening and insanely detailed at the best of times.


So it’s also understandable why the overwhelming majority of General Contractors opt for the path of least resistance when it comes to any of the above mentioned components. “Why try something new, when what we have works perfectly fine?” In fact, I’ll go one further, “Why try something new, when what we’ve been using for 200 years works perfectly fine?”


That’s where Portland Cement comes in. Portland Cement was invented in 1825 by a very clever English chap (aren’t they all) named Joseph Aspdin and since then the stuff has literally been used for absolutely everything. It simply is the actual foundation for our modern world. Need a new skyscraper - Portland Cement. Need a new exit ramp on the motorway - Portland Cement. A new sidewalk, a new shipping port, a new neighborhood, a new train station… I’ll give you three guesses. Yes, it’s Portland Cement for the lot of it! And as far as building materials go, it’s pretty good. It’s got roughly a 100 year lifespan before it needs a touch up or two, it’s readily available the world over and thanks to global appeal it’s cost effective as well. As far as the construction industry is concerned, it’s simply synonymous with who they are and what they do. Can you picture someone without any eyebrows? That’s the construction world without Portland Cement.


Giving credit where credit is due, Portland Cement is undoubtedly very good stuff, it’s been going gangbusters for 2 centuries and is partly responsible for my local Starbucks, so it’s a standing ovation for Portland Cement from me. Unfortunately it does have one major flaw; and like most things invented in the 1800s Portland Cement follows suit by simply dreadful for the environment. And I’m being kind there, dreadful is a titch of an understatement.


Apart from a rudimentary understanding, I would never claim to know the science behind Portland Cement production, but others do. According to the think tank Chatham House, Portland Cement is the third-largest C02 producer behind transportation and energy production. Portland Cement makes up 8% of global C02 emissions and that number is apparently rising annually. Calculating Portland Cement’s carbon footprint makes for some pretty grim numbers; for instance, one cubic yard of cement equals 400lbs of carbon. That’s 0.9 pounds of C02 for every pound of cement. And this doesn’t include the pollutants released into the environment when making Portland Cement - this includes vast amounts of nitrogen oxide, sulfur dioxide and my personal favorite, the ever mysterious particulate matter. All of this adds to air, ground and water pollution, again in huge numbers. So not good, but what’s the alternative?


Well, as you would expect there are many. All of them have pros and cons from cost effectiveness to readily available raw materials, but one which stands out is Geopolymer Concrete. Theorized to have been invented for the construction of the Pyramids of Giza (yes, those pyramids), Geopolymer Concrete was modernized from it’s ancient production recipe in the early 1970’s and has been refined and further modernized since.


Today’s Geopolymer Concrete has many advantages over Portland Cement, chief among them being its environmental impact or lack thereof. This comes from the fact that Geopolymer Concrete is produced using aluminosilicate waste materials that would be destined for the landfill or superfund site. These include Fly-ash, Slag, silica fume & kaolin to name a few and while not exactly carbon neutral, Geopolymer Concrete is considerably more environmentally sound with a low energy consumption than other cements and concretes including good old Portland Cement. Geopolymer Concrete is also stronger, has a longer lifespan, low shrinkage and it has freeze-thaw resistance, sulphate resistance and corrosion resistance in a natural occurrence of its production. It’s also surprisingly cost effective, given that it’s made up from recycled waste products.


So what are the disadvantages of Geopolymer Concrete, because you know there must be a few. These include a higher curing temperature than Portland Cement and are considerably weaker as well as prone to moisture while curing. But all these issues are reduced to nil after the concrete has dried. Geopolymer Concrete problem is efflorescence. These are white salty deposits which rise to the surface of the concrete after it’s completely dry, but at worst this is unsightly as opposed to structural. Now while these disadvantages can be overcome or worked around, there is one major issue with Geopolymer Concrete which simply can’t be overlooked, that being the availability of the raw materials required to produce Geopolymer Concrete. The same thing that makes this material so environmentally attractive is also it’s Achilles heel because there simply isn’t enough Fly-Ash or Slag to to produce enough Geopolymer Concrete in the quantities to start replacing Portland Cement, never mind the amounts required to knock Portland Cement off it’s 200 year throne as king of the construction world.


The good news is that Geopolymer Concrete is being used in limited quantities where and when it can for things like sea barrier walls, airport runways and new buildings in heavy earthquake prone areas. Other applications for Geopolymer Concrete are being discovered daily as are more readily available recipe components with similar properties to make newer versions of Geopolymer Concrete.


So is this the end of a 200 year run for Portland Cement, no of course not. Even if Geopolymer Concrete suddenly became as easy to make as a bowl of cereal, the companies who own and control the production of Portland Cement would never simply roll over for the sake of something as silly as the future of our planet. Add all the construction companies who would need to retool basic operations for the replacement of Portland Cement and you’d have nothing short of bedlam on your hands with construction projects around the world grinding to a halt almost overnight. This is an extreme and exceptionally cynical view I admit, but one that I believe happens to me more true than false.


As I mentioned above, I am not a science guy. The information in this piece was garnered from a couple of days research, a basic understanding and a natural curiosity, nothing more. To that point and to help you fill in the many gaps I’ve left, I’ve included some links below.


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