Scientists Re-Discover Recipe for “Roman Cement”

Ever won­der why con­crete struc­tures in the U.S. and the rest of the Anglo-world don’t last very long with­out con­stant touch-ups?  Sim­ple, it is the cement we’ve been using for over 200 years.

Called “Port­land Cement” after the Isle of Port­land in Eng­land, it has been the typ­i­cal recipe used in the West­ern World.  It’s prob­lem: It can’t with­stand repeated expo­sure to the ele­ments, often crack­ing and break­ing in a num­ber of years.  If that expo­sure includes sea­wa­ter, the cement lit­er­ally will break­down and dissolve.

There was another type of cement known to be around for over 2,000 years: “Roman Cement.”  As seen with the longevity of the Col­i­seum, it is supe­rior in every way over Port­land Cement.  The one prob­lem — No one wrote down the recipe and it was lost to history.

Not any­more, as sci­en­tists have finally cracked the code of Roman Cement, mak­ing its mass pro­duc­tion only a mat­ter of time.

As any­one who’s ever vis­ited Italy knows, the ancient Romans were mas­ter engi­neers. Their roads, aque­ducts, and tem­ples are still hold­ing up remark­ably well despite com­ing under siege over the cen­turies by waves of sack­ing maraud­ers, mobs of tourists, and the occa­sional earth­quake. One such struc­ture that has fas­ci­nated geol­o­gists and engi­neers through­out the ages is the Roman har­bor. Over the past decade, researchers from Italy and the U.S. have ana­lyzed 11 har­bors in the Mediter­ranean basin where, in many cases, 2,000-year-old (and some­times older) head­wa­ters con­structed out of Roman con­crete stand per­fectly intact despite con­stant pound­ing by the sea.


The researchers now know why ancient Roman con­crete is so supe­rior. They extracted from the floor of Italy’s Poz­zuoili Bay, in the north­ern tip of the Bay of Naples, a sam­ple of con­crete head­wa­ter that dates back to 37 B.C. and ana­lyzed its min­eral com­po­nents at research labs in Europe and the U.S., includ­ing at Berke­ley Lab’s Advanced Light Source. The analy­sis, the sci­en­tists believe, reveals the lost recipe of Roman con­crete, and it also points to how much more sta­ble and less envi­ron­men­tally dam­ag­ing it is than today’s blend.

That’s why the find­ings, which were pub­lished ear­lier this month in the Jour­nal of the Amer­i­can Ceramic Soci­ety and Amer­i­can Min­er­al­o­gist, are con­sid­ered so impor­tant for today’s indus­trial engi­neers and the future of the world’s cities and ports. “The build­ing indus­try has been search­ing for a way to make more durable con­cretes,” Jack­son points out.

Another remark­able qual­ity of Roman con­crete is that its pro­duc­tion was excep­tion­ally green, a far cry from mod­ern tech­niques. “It’s not that mod­ern con­crete isn’t good—it’s so good we use 19 bil­lion tons of it a year,” says Paulo Mon­teiro, a research col­lab­o­ra­tor and pro­fes­sor of civil and envi­ron­men­tal engi­neer­ing at the Uni­ver­sity of Cal­i­for­nia, Berke­ley. “The prob­lem is that man­u­fac­tur­ing Port­land cement accounts for 7 per­cent of the car­bon diox­ide that indus­try puts into the air.”

The secret to Roman con­crete lies in its unique min­eral for­mu­la­tion and pro­duc­tion tech­nique. As the researchers explain in a press release out­lin­ing their find­ings, “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.”

The Port­land cement for­mula cru­cially lacks the lyme and vol­canic ash mix­ture. As a result, it doesn’t bind quite as well when com­pared with the Roman con­crete, researchers found. It is this infe­rior bind­ing prop­erty that explains why struc­tures made of Port­land cement tend to weaken and crack after a few decades of use, Jack­son says.

Adopt­ing the mate­ri­als (more vol­canic ash) and pro­duc­tion tech­niques of ancient Roman could rev­o­lu­tion­ize today’s build­ing indus­try with a stur­dier, less CO2–inten­sive con­crete. “The ques­tion remains, can we trans­late the pricini­ples from ancient Rome to the pro­duc­tion of mod­ern con­crete? I think that is what is so excit­ing about this new area of research,” Jack­son says.

Roman con­crete will be as win-win a sce­nario as you can get.  Small gov­ern­ment con­ser­v­a­tives will see roads that last much, much longer than before caus­ing infra­struc­ture projects last­ing longer and in less need of short-term repair costs, while envi­ron­men­tal lib­er­als will be pleased to know that mak­ing Roman cement is more CO2-friendly than the tra­di­tional method behind Port­land cement.

So, let’s get paving the Roman way.

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  • Bil­liam

    Worry not! If any­thing can screw this up, it’s the Gov­ern­ment. The Gaia wor­shipers will get with the EPA, and voila! Instant screw up.

  • kev­in­bin­ver­sie

    Not to men­tion the road-builders lobby who will go “Wait a sec­ond, longer last­ing roads? We can’t have that!”

  • Bil­liam

    Hang it all! I for­got the road builders. As well as all those union jobs hold­ing signs..