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Geopolymers: Promising Materials For Underground Applications
There was a time when engineers designed structures to last for eternity. Since the beginning of mankind, civilizations have desired to create an enduring legacy through their architecture. Engineers from ancient civilizations such as Egypt, Greece and Rome did not build their fabulous structures and monuments with the intention of having them repaired every 50 years.
In fact, many of those structures, even when they have been neglected for centuries, damaged through wars, or intentional destruction, are still with us. The Parthenon, the Roman Coliseum and the Egyptian Pyramids are the standing testimonies of the ingenuity of ancient engineering minds as well as the power of the empires they lived in.
Although the construction of palaces, temples and roads are primary examples of the great constructions of the past, underground construction was not an exception to this design philosophy. For example, the Cloaca Maxima, a wastewater collector running beneath the city of Rome, is still in service after 2,000 years – something hard to demand from modern sewer systems. Many similar Roman sewer systems can still be found across Europe. One valid question for modern times is whether it is possible to re-think the design of structures in order to provide a service life that is measured by hundreds, rather than tens of years.
Although the most logical solution in terms of durability is to use natural rock as a construction material, the fast pace of modern construction projects, along with a lack of suitable materials in many areas, make it unaffordable to use rocks such as marble or granite with limited exceptions. We have become accustomed to the great versatility of Portland cement. In fact, our entire construction industry currently depends on it.
The invention of Portland cement was certainly a revolution for construction materials as it helped shorten construction times and reduce labor considerably. This has made concrete the second most used substance in the world after water. However, as the industry grew and Portland cement evolved into becoming the single most important material for construction, the very important aspect of material durability was slowly pushed aside, which resulted in engineers no longer considering hundreds of years of service life when planning the construction of their structures. Buildings are constructed faster now, but must be rebuilt sooner as well. Especially in North America, it is now 60 years after the majority of the road infrastructure was constructed and many of our constructions are approaching the end of their intended design life. We are in a crisis of rehabilitation.