What raw materials are in concrete

The crazy luxury hotel that Frank Schätzing came up with for his space thriller "Limit" is called "Gaia" and is located on the moon. It is noteworthy that mankind lives out its already often subterranean sexism debate there in space, which is why the male architects initially devised their Gaia, the mythical mother of all life, as a concrete female figure with large breasts similar to Venus von Willendorf. The hotel manager is not at all enthusiastic about this planned "Monument of the Pugs" and advocates a more androgynous form. One agrees on something mean.

Much more interesting than this attempted dispute is the only half-fictionalized, actually futuristic building material twist that is also carried out in this novel. The managers of the acutely crisis-ridden cement and concrete industry from Heidelberg Cement to Dyckerhoff should listen carefully. Because they are running out of sand as the most important building raw material of our epoch not only in Germany (in itself a top-quality sand country), but also worldwide.

The quartz grains have already become - after water - the most consumed natural raw material in the world. Our world is built on sand. The material is not only found in houses, bridges and streets, but also in toothpaste and smartphone screens. "Sand is the megastar of our industrial and electronic age": That is the conclusion of ETH Zurich. Annual consumption is estimated at around 50 billion tons. But the natural value and material of modernity is running out. That is known. But this is also increasingly relevant for building culture, because glass and concrete, made from sand, are the ubiquitous building materials that have become iconic in recent times to this day. So we not only lose the material, but also the consensus of the form.

Concrete as a symbol of modernity

The building history is inconceivable without concrete, an early variant of which goes back to Roman antiquity as "opus caementitium", while certain mortar mixtures were used in Turkey more than 10,000 years ago. But it was not until the 20th century that concrete became a stone of desire, a miracle in construction. What the construction industry is now hoping for: At least in Schätzing's novel, Gaia is made of moon dust. More precisely from regolith, which, as experiments by NASA have already shown in reality, could actually be compacted with carbon and epoxy resin to form "moon concrete". Theoretically. What builders like about it: This moon concrete would be more durable and even cheaper than conventional concrete.

Unfortunately, it still remains to be clarified how the 400,000 kilometers that will soon be 400,000 kilometers apart, which separate the moon from the major construction sites in Dubai, Moscow or the Munich parcel post hall area, can be cost-effectively still need to be clarified. The furious idea of ​​a space elevator has existed since the 1960s, but not even Elon Musk, who otherwise believes everything, thinks that the moon can be exploited as a substitute resource in the near future.

However, this is astonishing: The earth's natural sand reserves, which are suitable for building as an indispensable raw material for cement and concrete, are also running out as a result of an almost hysterical, out-of-control building boom around the world - you think about how to do it hit the cosmic neighborhood. Instead of thinking about an end to building or about building with different materials. Humanity as a whole is obviously resistant to advice. In the novel, by the way, Gaia at least blows up in the end. At least in the air of the vacuum.

Occasionally you can hear why there is still really enough sand, especially as one of the consequences of climate change. It is correct: there are more and more deserts and, as a result of the karstification and sanding of entire stretches of land, logically more sand on earth. However, due to its grain size, this sand, rounded by wind and weather, is not well suited to compacting itself into concrete with the necessary aggregates. How to do it anyway is the subject of research - and the first patents have already been issued for this - but the processes are probably not yet economical. One speaks of the sand paradox: there is both enough and too little usable sand.