Cement
(I wrote this text – originally in German – as part of a university course I was teaching on Sustainability in 2019. Part of the course dealt with the concept of the Anthropocene. I read the text to my students on a walk we took through our campus, on which we made a stop at a construction site.) Depending on who you ask, cement has either a long or a very long history: some historians trace the origins of cement back to ancient Egypt, around five thousand years ago. The ancient Egyptians probably used a mixture of straw and mud as a binding agent. Basically, cement means no more than that: caementicium, the Latin origin of the word, first meant “crushed stone” and later “binding mass”. The fact that the word cement has a Latin origin is no coincidence either: ancient Romans around the 250-150 BC also started using cement, but they did such a good job of that, that the word has survived to this day – and so has their manufacturing process. Incidentally, ancient Romans mainly used cement for their more grandiose buildings: the Pantheon, the Colosseum, and a number of walls, domes, bridges and aqueducts. However, cement was also very useful for the Roman sewage system that was being developed at the time and for the expansion of the huge road network. Still, we know – most famously because of the huge fire under Emperor Nero – that wood was still by far the most common building material. And it would take quite a while longer before cement became as ubiquitous as it is today. For all its ubiquity, I was a little surprised at how little I, as a 21st century person and therefore someone who encounters cement on a daily basis, knew about it when I started researching this topic: One of the crazier facts about cement is that the recipe for cement was briefly lost completely after the collapse of the Roman Empire, ushering in a cement-free era until it was rediscovered by the British engineer John Smeaton in the late 18th century. Incidentally, this is almost a century after Hans Carl von Carlowitz and his explanations on sustainable forestry. And it is also after the start of the industrial revolution. From then on, of course, everything happened in quick succession and today cement and concrete are as ubiquitous in the design of our human world as only plastic, steel or the internet. Today, there are almost 40 tons of concrete for every person on earth. That’s not a lot in Germany – a simple single-family house already exceeds this amount by at least twice as much. Every year, however, around half a ton per person is added and we are not stopping there. Between 2011 and 2013, China alone poured more concrete than the USA did during the entire 20th century. Concrete has become a human signature, a material that will still be detectable in the ground millions of years later and long after the supposed end of mankind. And it has taken on cultural significance: Raw concrete is chic and modern – at least it was 5-10 years ago – skate parks get their urban charm from the heavy use of concrete, and even art objects, gravestones and statues are cast in concrete to decorate our cultural landscape. And yet it is important to recognize how new our cement and concrete culture is. The history of humankind without cement is sixty times as long as that with cement. And we already know that cement also has its disadvantages: Among other things, it seals surfaces that would normally create a cooler urban climate and it emits CO2 during its production. Perhaps that’s why, when I’m on Facebook, Instagram, Pinterest or Reddit, I keep coming across pictures of daring wooden constructions that are supposed to replace concrete high-rises or pictures of tree house vacation homes with a built-in sauna and loft bed. But I’m not actually ready to give up concrete yet. I enjoy being able to flush my toilet knowing that all my waste is being disposed of in huge cemented pipes under the city and it always upsets me a little when my bus has to travel that short distance over non-cemented, cobblestone pavement on the way home and I get a good shake. I think that’s how many of us feel and that’s why we will continue to pour concrete for the time being, our urban planners will design green spaces on roofs and our researchers will work on making cement less harmful to the environment. That will have to be enough for now.
