Conventional concrete and seawater are a problematic mix. The corrosive nature of salt, and the weathering effects of tides and wind can cause significant deterioration in a matter of decades. Contrast that with concrete sea walls built by ancient Romans two thousand years ago. The remnants of those structures still stand off the coast of modern day Italy and other sites that comprised the former empire. Quite surprisingly, these formations are stronger than they were centuries ago. As scientists unlock the mystery of why that’s true, modern engineers may gain valuable lessons on stronger infrastructure.
Image Source: Wikimedia
Self-Fortifying Sea Walls
The Roman sea walls are built from a concrete made of volcanic ash from the region and quicklime. The combination has been called “the most durable building material in history”, but there’s more to the substance than the sum of its parts. When the mixture is subjected to seawater, a chemical reaction occurs in which part of the substance is corroded away but new minerals are formed in its place. This not only prevents cracking and pitting that affects modern, marine-based concrete structures, it gradually increases the strength of the material. The result is essentially a self-fortifying sea wall.
Image Source: The Washington Post
Imitating The Recipe For Roman Concrete
Even as scientists are gaining a new understanding of the ancient concrete’s composition and structural capabilities, they still haven’t pinned down an exact “recipe” to be reproduced for the building of modern structures. Another obstacle is the currently limited amount of volcanic ash and rocks that ancient Romans used to make their concrete. Researchers are however testing various materials to create a potential substitute.
Reducing Repairs And Cutting Carbon
The value in utilizing a self-strengthening building material comes from its long term structural integrity, as well as its potential to reduce the carbon footprint infrastructure. With current concrete production contributing as much as five percent of global CO2 emissions, reduced need—due to fewer repairs—could have significant positive impact on carbon reduction. Additionally, self-strengthening concrete could eliminate or reduce the need for steel reinforcements, which also corrode in marine environments.
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