Fundamental for the development of large metropolises as we know them today, cement is a material used historically, whose technological advances have revolutionized construction technique and technology of civil construction, enabling the verticalization of construction and the densification of urban centers. Cement, both added to water and sand to make mortar and combined with steel and aggregate to form concrete, performs different functions in a work, from structure to finish.
If, on the one hand, concrete is the second most used substance on the planet, after water, on the other hand, its production chain is among the most polluting in the world. The dependence that the urban environment created for cement and its derivatives, including concrete, began a long time ago. The civilizations of Ancient Egypt and Ancient Greece, for example, already mixed different types of ground rocks with liquids to create adhesive mortars to assist in the construction of structures. The builders of the Roman Empire, in the 4th century BC, created a combination of lime, pozzolan and sand, experimenting with animal fat, milk and blood to incorporate air into the mixture and created what we now call concrete.
The use of derivatives of this plastic mortar by the Romans represents three fundamental characteristics that justify the dependence on concrete these days: Firstly, concrete can be molded from shapes to assume specific volumes, expanding constructive possibilities beyond what was possible by stacking blocks and stones. Secondly, this moldable mass reached structural strength just like the stones, being able to replace them. And thirdly, this mass was also resistant to water, and could not only work as a waterproofing agent but also be installed on flooded land as a base for constructions, which allowed the occupation of new territories.
Thus, mortars and concrete were developed in our societies from the demand of architecture and engineering. In the early 1850s, Joseph Louis Lambot made an important technological advance by combining the malleability, strength, and impermeability of cement with steel rods to develop a reinforced mortar boat. His invention was the basis for what is now one of the main forms of construction in the world's great metropolises: reinforced concrete. It is, therefore, cement that enables the verticalization of cities, as well as their densification, not only through reinforced concrete, but also through other functions it assumes in construction:
Foundation
In-Place Moldable Structure
Prefab Structure
Finishing
Furniture
The extraction of cement, and all the processes involved in its production chain, represent a great risk to the environment due to the emission of carbon dioxide in the atmosphere and also the damage that mining causes in its territory. According to the latest IPCC report, there are only 11 years left to reduce emissions and prevent irreversible damage from climate change. Which means that this production chain needs to be changed so that we can reverse global warming.
Source: Kaefer, Luís Fernando. 1998. A Evolução do Concreto Armado.
Editor's Note: This article was originally published on September 15, 2022.
