How Did the Romans Make Concrete That Lasts Longer Than Modern Concrete? The Mystery Finally Solved

An explo­sion in recent years of so-called “ruin porn” pho­tog­ra­phy has sparked an inevitable back­lash for its sup­posed fetishiza­tion of urban decay and eco­nom­ic dev­as­ta­tion. Doc­u­ment­ing, as the­o­rist Bri­an McHale writes, the “ruin in the wake of the dein­dus­tri­al­iza­tion of North Amer­i­can ‘Rust Belt’ cities” like Detroit, “ruin porn” shows us a world that only a few decades ago, thrived in a post-war eco­nom­ic boom that seemed like it might go on for­ev­er. Our mor­bid fas­ci­na­tion with images from the death of Amer­i­can man­u­fac­tur­ing offers a rich field for soci­o­log­i­cal inquiry. But when sci­en­tists look over what has hap­pened to so much of the archi­tec­ture from the ear­ly to mid-twen­ti­eth cen­tu­ry, they’ve most­ly had one very press­ing ques­tion:

What is going on with the con­crete?

Or more specif­i­cal­ly, why do struc­tures built only a few years ago look like they’ve been weath­er­ing the ele­ments for cen­turies, when build­ings thou­sands of years old, like many parts of the Pan­theon or Trajan’s Mar­kets in Rome, look like they’re only a few years old? The con­crete struc­tures of the Roman Empire, writes Nicole Davis at The Guardian, “are still stand­ing more than 1,500 years after the last cen­tu­ri­on snuffed it.” Roman con­crete was a phe­nom­e­nal feat of ancient engi­neer­ing that until recent­ly had stumped sci­en­tists who stud­ied its dura­bil­i­ty. The Romans them­selves “were aware of the virtues of their con­crete, with Pliny the Elder wax­ing lyri­cal in his Nat­ur­al His­to­ry that it is ‘impreg­nable to the waves and every day stronger.”

The mys­tery of the Roman con­crete recipe has final­ly been revealed. Researchers at the Uni­ver­si­ty of Utah have just pub­lished a study in Amer­i­can Min­er­al­o­gist show­ing how the com­pound of “vol­canic ash, lime (cal­ci­um oxide), sea­wa­ter and lumps of vol­canic rock” actu­al­ly did, as Pliny claimed, become stronger over time, through the very action of those waves. “Sea­wa­ter that seeped through the con­crete,” notes Davis, “dis­solved the vol­canic crys­tals and glass­es, with alu­mi­nous tober­morite and phillip­site crys­tal­iz­ing in their place.” These new crys­tals rein­force the con­crete, mak­ing it more imper­vi­ous to the ele­ments. Mod­ern con­crete, “by con­trast… is not sup­posed to change after it hardens—meaning any reac­tions with the mate­r­i­al cause dam­age.” (The short video above explains the process in brief.)

The recent study builds on pre­vi­ous work con­duct­ed by lead author, Uni­ver­si­ty of Utah geol­o­gist Marie Jack­son. In 2014, Jack­son, then at the Uni­ver­si­ty of Cal­i­for­nia, recre­at­ed the Roman con­crete recipe and dis­cov­ered one of the min­er­als with­in it that makes it supe­ri­or to the mod­ern stuff. But it took a cou­ple more years before she and her col­leagues fig­ured out the role of sea­wa­ter on form­ing the rare crys­tals. Now, they are rec­om­mend­ing that builders begin using Roman con­crete in the near future for sea­walls and oth­er marine struc­tures. The research “opens up a com­plete­ly new per­spec­tive for how con­crete can be made,” says Jack­son. “What we con­sid­er cor­ro­sion process­es can actu­al­ly pro­duce extreme­ly ben­e­fi­cial min­er­al cement and lead to con­tin­ued resilience, in fact, enhanced per­haps resilience over time.”

As we increas­ing­ly turn our post­mod­ern gaze toward the fail­ures of post­war industrialization–toward not only crum­bling cities but crum­bling dams and bridges–one secret for build­ing infra­struc­ture that can last for cen­turies comes to us not from an algo­rithm or an AI but from an ancient recipe com­bin­ing the primeval forces of vol­ca­noes and ocean waves.

via The Guardian

Relat­ed Con­tent:

Roman Archi­tec­ture: A Free Course from Yale 

Rome Reborn: Take a Vir­tu­al Tour of Ancient Rome, Cir­ca 320 C.E.

Ancient Rome’s Sys­tem of Roads Visu­al­ized in the Style of Mod­ern Sub­way Maps

Josh Jones is a writer and musi­cian based in Durham, NC. Fol­low him at @jdmagness

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Comments (8)
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  • Fred says:

    Because we use steel in our con­crete using salts to enhance cor­ro­sion would be a prob­lem.

  • Peter Asher says:

    Car­bon fiber?

  • Incred says:

    What, we’re adding salt to increase cor­ro­sion???

  • Joe McGuckin says:

    Ahh, I call bull­shit on this. This top­ic has been float­ing around the net for months now. All PCC con­crete’s con­tin­ue to cure over time.
    There’s noth­ing mag­ic or secret about this phe­nom­e­non. Mod­ern con­crete con­tin­ues to cure (not ‘hard­en’) for an indef­i­nite amount of time.
    30 year old struc­tures are stronger than a just poured one.

  • Flash says:

    Go fig­ure, the Romans didn’t need rein­force­ment wire

  • Lakew Gebeyehu says:

    Dear Sirs,

    I reaď yòur reaserçh arti­cle on Roman con­cret mak­ing and I want to try to pro­duce gardeb path and curbs. Vol­canic ash, pumìce and lime­stone are avail­able but no sea water only coun­cile water suply. Can you advise me how to go with the mix ratio. The cost of port­land cement has sky rock­et­ed plus it has become lit­er­al­ly imposi­ble to buy even 1 quin­tal.

    Best Regards.


  • Ron Onimous says:

    Sea­wa­ter can be approx­i­mat­ed by mix­ing one mea­sur­ing cup of salt into one gal­lon of fresh­wa­ter, sea­wa­ter mix­es are avail­able in pet stores for marine aquar­i­ums, and marine aquar­i­um owners/caretakers would prob­a­bly give away free salt­wa­ter when per­form­ing water changes on their tanks.

  • Edawen says:

    Pet store sea salt is expen­sive. It’d be cheap­er just buy­ing salt in bulk per­haps the type that’s used for salt­ing roads, or used for swim­ming pools.

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