How is it possible that structures built more than 1,500 years are still in tact while a concrete building built merely 15 years ago already shows signs of wear? It's an answer that scientists have been continuously seeking for years and after years of research, they may have finally found it.

While the exact recipe for the concrete used by the Romans has never been uncovered, scientists have speculated what materials it contains. According to The Guardian, the Roman recipe consisted of a mix of volcanic ash, lime (calcium oxide), seawater and lumps of volcanic rock. While none of these materials seem inherently strong, scientists claim that the strength came from a combination of the materials as well as numerous processes.

One theory regarding how the structures have gained their strength mentions the result of the seawater reacting with volcanic material in the cement thus creating new minerals that reinforced the concrete. While the process sounds simple, the strength of the concrete didn't occur instantaneously. The video above reveals how it's a gradual process that can only develop over time as the seawater "corrodes" the mixture and forms new minerals. The newly formed minerals are what help to prevent cracks in the concrete and strengthen the structure.

Marie Jackson, a geologist at the University of Utah and co-author of a study into Roman structures, revealed to The Guardian that she found "[an] abundance [of] tobermorite growing through the fabric of the concrete, often in association with phillipsite [another mineral]." when examining the concrete. She suggests that when the seawater seeped through the concrete, it eventually dissolved the volcanic crystals and glasses with aluminous tobermorite and phillipsite crystallizing in their place. The minerals produced by this process are believed to be responsible for making the structures stronger over time since the minerals grew.

So is the key element for stronger concrete a matter of allowing it to crystallize inside? Essentially, yes. Compared to the Roman concrete, modern concrete is made with the intention of not changing after it hardens. This means that any reaction the concrete has to other elements is more likely to result in damage rather than structural strength. If however, we adapt our concrete, we could see major improvements in sustainability. According to Jackson, the research conducted on the roman concrete, "opens up a completely new perspective for how concrete can be made - that what we consider corrosion processes can actually produce extremely beneficial mineral cement and lead to continued resilience, in fact, enhanced perhaps resilience over time."

So why aren't we using this method? Mostly because a lot of work still needs to happen before the mixture can be perfected. As mentioned prior, the recipe for the mixture has never been found so while scientists are making advancements towards learning what is giving the concrete strength, there has yet to be a definitive answer on the composition of the concrete. Luckily, this research has brought them closer to finding the answer but there's still a long process ahead.

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