Concrete is currently the most important artificial building material. But modern concrete harbours major problems that have increasingly made the headlines in recent years:

• The production of concrete requires large quantities of river sand and gravel. Both will no longer be available in unlimited quantities in the future.
• Concrete has an extremely poor ecological balance. In its production, Portland cement is used as a binding agent for this river sand and gravel in combination with water. For every tonne of cement needed, about 0.8 tonnes of CO₂ are released. Because of the huge quantities of cement consumed worldwide (about four billion tonnes in 2016), the cement industry is responsible for five to eight percent of anthropogenic carbon dioxide emissions. By comparison, all air travel in 2018 resulted in CO₂ emissions of about 700 million tonnes. Emissions from the cement industry were well over two billion tonnes of CO₂ in the same period.
• The increasing taxation of CO₂ will make cement and thus concrete much more expensive in the future.
• Concrete is only stable up to temperatures of around 500 degrees Celsius.