Our national flower is the concrete cloverleaf. ~ American historian and sociologist Lewis Mumford
By weight, concrete is the 2nd-most-consumed substance on Earth, behind water. On average, every person on the planet chews through 2.7 tonnes of cement each year. 4.3 billion tonnes were consumed worldwide in 2014. Concrete is used to build roads, runways, sidewalks, bridges, buildings, and dams.
China consumes over half the cement made, and produces 60% of it, followed at a distance by India and the US.
Concrete-like materials were used by Levant Arabs in 6500 bce. By 700 bce they had discovered the advantages of mortar made of hydraulic lime, whereupon kilns were built to construct rubble-wall houses with concrete floors.
The Arabs also constructed underground waterproof cisterns, the locations of which they kept to themselves. This secret water supply let them thrive in the deserts where they lived (after having deforested the land millennia prior).
The first people to employ concrete on a large scale were the ancient Romans, who were eager employers of the hard stuff. The Roman Colosseum was made of concrete, as were the other grand buildings that pronounced the prowess of the Empire.
After the Roman Empire collapsed, concrete was largely forgotten until its redevelopment in England during the mid-18th century, whereupon concrete was used to build the modern urban jungle.
The primary ingredient in concrete is cement, which is made today by heating limestone and clay until it fuses into a material called clinker, which is then combined with gypsum: the sulfate stuff from which plaster and blackboard chalk are made. The kilns used to create clinker are commonly fueled to extremely high temperatures by coal.
The concrete that the Romans made is superior to the modern variety. Chemical reactions on modern concrete after it hardens can only be damaging. In contrast, Roman concrete becomes stronger with time.
The Roman cement recipe was a mix of volcanic rubble and ash, lime (calcium oxide), and seawater. That combination naturally generates heat, turning the conglomeration into concrete. Whereas seawater degrades modern concrete, it strengthens Roman concrete by creating new minerals which fill any cracks and reinforce the material’s structure.
Open-pit mining for limestone is environmentally destructive. Both the intense heating and the chemical reactions involved in cement manufacture produce prodigious amounts of carbon dioxide. Cement production contributes 5% of all fossil-fuel-based CO2 emissions worldwide.
The great weight of cement makes it tough to transport; so markets are localized. But the local nature of cement has not stopped the capitalist urge for control. Just 5 behemoth firms dominate the global market.