Monday, 19 August 2013

Concrete that actually lasts

On more than a few occasions I’ve pondered why balconies on apartment buildings not even as old as I am need to be replaced, and why bridges not even a half century old are crumbling. And that has led me to also wondering why stuff the Romans built is still standing millenia later.

I know infrastructure the latitude I’m living at suffers from salt damage from snow and ice removal, and also ground swell from thawing and freezing, but that doesn’t really explain balconies 25 stories up. Overpasses maybe.

I’ve previously pondered why no one seems capable of building a proper retaining wall anymore. The Romans knew what was required thousands of years ago, but now all we get are inept efforts guaranteed to fail. The cynic in me has to wonder whether this isn’t a deliberate ploy to generate a never ending stream of repairs and fixes and rebuilds.

Whether this will ever be adopted so that when expensive infrastructure is rebuilt it will actually stand for centuries rather than decades remains to be seen. But at least they know how the Romans managed to build harbour breakwaters and other structures that are still standing, still in use, no repairs necessary.

“The Romans made concrete by mixing lime and volcanic rock. For underwater structures, lime and volcanic ash were mixed to form mortar, and this mortar and volcanic tuff were packed into wooden forms. The seawater instantly triggered a hot chemical reaction. The lime was hydrated—incorporating water molecules into its structure—and reacted with the ash to cement the whole mixture together.”

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