What We Can Re­ally Learn From An­cient Ro­man Con­crete

Traveling Minds - - Table Of Contents -

The se­cret to why con­crete struc­tures built in the time of An­cient Rome are still stand­ing may have fi­nally been fully dis­cov­ered. It turns out that the Ro­mans re­ally knew what they were do­ing when they built with con­crete, in con­trast to mod­ern man whose con­crete struc­tures rarely last longer than 100 years.

Some of the con­crete struc­tures in An­cient Rome are not only still stand­ing but, if any­thing, are prob­a­bly even stronger than ever. By con­trast, the same types of struc­tures built in mod­ern times of­ten only last sev­eral decades. Bridges are fre­quently re­moved and re­built af­ter only 50 years, and road­ways are con­stantly in need of re­pair. Build­ings may last longer, but they of­ten reach a time for tear­down and re­place­ment that is not just dic­tated by the de­sire to con­struct a more mod­ern build­ing.

Ac­cord­ing to Marie Jack­son, a Univer­sity of Utah ge­ol­o­gist, part of the rea­son for this dif­fer­ence con­cerns the na­ture of the con­crete used. Back in An­cient Ro­man times, the con­crete mix­ture in­cluded lime and sea wa­ter as a starter base, which the builders then mixed with vol­canic rock (that era’s ag­gre­gate). They did this in part be­cause that kind of rock was widely avail­able at the time but also be­cause they had ob­served nat­u­rally oc­cur­ring de­posits of tuff – ig­neous rock that con­tains frag­ments of bedrock, tephra and vol­canic ash. The Ro­mans copied what Mother Na­ture had care­fully laid out in front of them.

When con­ven­tional Port­land ce­ment is cured, there is a hy­dra­tion re­ac­tion that pro­duces two very dif­fer­ent by-prod­ucts. One is cal­cium sil­i­cate hy­drate (CSH), a sub­stance that forms the glue that binds the ag­gre­gates to­gether. A sec­ond is cal­cium hy­drox­ide (CH), which, un­for­tu­nately, works in op­po­si­tion to the CSH and ac­tively helps un­der­mine the strength of the Csh-ag­gre­gate bonds. This is part of why mod­ern con­crete is in­ten­tion­ally de­signed to be as in­ert as pos­si­ble, be­cause, oth­er­wise, the pres­ence of the CH would tend to pre­ma­turely tear apart the con­crete.

The ma­te­ri­als the An­cient Ro­mans se­lected for their con­crete mix­ture in­cluded the nat­u­ral pumice poz­zolan, a com­pound present in the vol­canic ma­te­ri­als there that “switches on” what is to­day re­ferred to as a “poz­zolanic re­ac­tion” when mixed with the hy­drated con­crete paste. That re­ac­tion ends up con­vert­ing a sig­nif­i­cant amount of the use­less CH by-prod­uct into more of the CSH. The poz­zolanic re­ac­tion, there­fore, ef­fec­tively makes the con­crete stronger even from the first day it is poured.

As Jack­son looked fur­ther into com­par­ing the old Ro­man struc­tures to mod­ern ones, she be­gan notic­ing other dif­fer­ences. One im­por­tant one (be­yond the poz­zolanic re­ac­tion process) was the pres­ence of ex­ten­sive min­eral in­ter­growths that ex­ist be­tween the vol­canic ag­gre­gates and the an­cient con­crete mor­tar. Those in­ter­growths keep the nat­u­ral cracks that oc­cur in any con­crete over time from widen­ing in the Ro­mans’ ver­sion. In mod­ern Port­land ce­ment struc­tures, there are no such in­ter­growths to hold things to­gether.

The last dis­cov­ery made by Jack­son was a big sur­prise and is per­haps the real se­cret to the longevity of the older con­crete. Jack­son and her team were given a chance to eval­u­ate drill cores of con­crete gath­ered from An­cient Ro­man har­bors. Within those cores was a very rare min­eral, alu­mi­nous to­ber­morite (Al-to­ber­morite). Not only does it show up very rarely in na­ture but it is also ex­tremely dif­fi­cult to syn­the­size, es­pe­cially at the rel­a­tively low nat­u­ral tem­per­a­tures present there.

Af­ter (lit­er­ally) dig­ging fur­ther – and with the help of ex­otic ex­am­i­na­tion tools like mi­crod­iffrac­tion and mi­croflu­o­res­cence pro­vided by the Lawrence Berke­ley Na­tional Lab­o­ra­tory – Jack­son’s team saw that both Al-to­ber­morite and phillip­site, a sim­i­lar min­eral, had formed in the pumice par­ti­cle and mi­cro­p­ores within the ce­ment­ing ma­trix. Their spe­cific crys­talline shapes tend to hold ag­gre­gates tight over time.

This re­search de­fined the raw ma­te­ri­als present in the con­crete mix­ture, but there was still one miss­ing piece of the puz­zle: how the de­posits could grow over time. What the team fig­ured out, af­ter even more study, is that the reg­u­lar soak­ing of the ma­rine con­crete de­posits with sea wa­ter caused the nor­mally-quite-cor­ro­sive briny wa­ter mix­ture to pen­e­trate through the unique con­crete struc­ture. As each new splash of wa­ter made it through, some of the vol­canic ash present dis­solved. The re­sult­ing slurry then pro­vided a base for new min­er­als to grow and then bond with the ag­gre­gates and al­ready-ex­ist­ing con­crete.

The re­sult was a con­crete mix­ture that, over time, not only healed it­self of mi­nor cracks but also be­came stronger with each suc­ceed­ing wave – pro­vided, of course, that the waves in­volved were not too in­tense.

In the end, the com­bi­na­tion of the pres­ence of vol­canic ma­te­ri­als in the ag­gre­gate, the vol­canic ash, the re­sult­ing poz­zolanic re­ac­tion, the pres­ence of Al-to­ber­morite and phillip­site in the end prod­uct and then the con­stant wash­ing by sea wa­ter pro­duced a con­crete that did more than just sur­vive over time. It thrived.

The An­cient Ro­man so­lu­tion also did one other thing that puts it far ahead of con­ven­tional Port­land ce­ment: Its cre­ation pro­duced a lot less car­bon diox­ide.

In con­trast to the rel­a­tively low tem­per­a­ture and nat­u­rally oc­cur­ring poz­zolanic chem­i­cal re­ac­tion men­tioned above, Port­land ce­ment is made by heat­ing lime­stone to over 2,000°F. This not only re­quires a great deal of fos­sil fuel en­ergy (just to heat the lime­stone) but the rea­son for heat­ing the lime­stone is in part to bake the em­bed­ded CO2 out of the nat­u­rally oc­cur­ring com­pound built into the tiny ma­rine or­gan- ism struc­tures that helped form the lime­stone in the first place. The com­bi­na­tion of both ends up re­leas­ing a great deal of CO2 into the at­mos­phere.

The to­tal amount of CO2 emit­ted cur­rently in the process of mak­ing Port­land ce­ment works out to be about a pound of CO2 cre­ated for ev­ery pound of Port­land ce­ment man­u­fac­tured. And there are bil­lions of tons of Port­land ce­ment man­u­fac­tured through­out the world ev­ery year.

Con­trast that with the man­u­fac­tur­ing process of the An­cient Ro­man ma­rine con­crete. In that process, the poz­zolanic re­ac­tion ac­tu­ally con­sumes some of its waste prod­ucts as it cures. It is also “man­u­fac­tured” with­out the 2,000°F fos­sil-fuel-pow­ered kilns needed for Port­land ce­ment. It is there­fore far “greener” and far less dam­ag­ing to the en­vi­ron­ment, with an es­ti­mated to­tal car­bon foot­print that’s less than one-tenth that of its mod­ern coun­ter­part. And this only takes into con­sid­er­a­tion the ini­tial man­u­fac­tur­ing process. When you con­sider longevity, the car­bon sav­ings are vastly more.

Now that the An­cient Ro­man con­crete recipe has been re­dis­cov­ered, the next step for Jack­son’s team is to see if there is a way to rein­vent it for mod­ern times and ac­tu­ally con­vince peo­ple to use it. That could re­sult in ma­jor value for the con­struc­tion in­dus­try – and be­yond.

What the re­searchers have not thor­oughly ex­plored is just how the Ro­mans came to de­velop such tech­nol­ogy. Was it re­ally de­vel­oped by ac­ci­dent, just from us­ing ma­te­ri­als read­ily avail­able to them, or was the knowl­edge handed down to them from an even ear­lier civ­i­liza­tion?

While main­stream ar­chae­ol­o­gists dis­agree, the an­cient Egyp­tians had their own meth­ods for pro­duc­ing long-last­ing con­crete, and some of the stones in the great pyra­mids were cast con­crete, not stone blocks.

The story of how those pyra­mids were built is well­known to many brought up in Western coun­tries. Sup­pos­edly there were great stone quar­ries in ex­is­tence at a dis­tance from the con­struc­tion site. From there, large stone blocks were cut out, us­ing the tools of the time – sup­pos­edly tools made of cop­per, a com­mon enough but soft metal. Thou­sands of la­bor­ers – who in­vested sweat and blood and of­ten died in the process – were in­volved in ev­ery build. That part has been ex­plained – and even fan­ta­sized – in chil­dren’s books and in movies like The Ten Com­mand­ments. It is part of our com­mon mythol­ogy about this once-great an­cient civ­i­liza­tion.

Strangely, though, for a peo­ple who doc­u­mented al­most ev­ery as­pect of their lives so well, this pyra­mid-build­ing thing, which must have con­sumed a great amount of time and many peo­ple to man­age, was some­how never doc­u­mented in the Egyp­tians’ hi­ero­glyphs. All that cut­ting of stones, mov­ing them to the assem­bly site and lift­ing them up with ramps re­sulted in no im­ages at all. And there are also no signs of the hous­ing where the work­ers would have lived – nor are there any traces of the tools they sup­pos­edly used to carve out the stones.

As in any sci­en­tific field, it took some strong cre­ative thinkers to con­sider another op­tion. One of the more rad­i­cal of th­ese thinkers was Joseph Davi­dovits, a French ma­te­ri­als sci­en­tist. His an­swer to the puz­zle, put forth in the mid-1980s, was that the rea­son there was no great hous­ing tracts, no trace of the tools and no il­lus­tra­tions or telling of the con­struc­tion process sug­gested above was that it all never hap­pened. In­stead, Davi­dovits hy­poth­e­sized that the Egyp­tians cre­ated the blocks used to build the pyra­mids with con­crete poured on-site into wooden molds.

The con­crete he imag­ined has some sig­nif­i­cant sim­i­lar­i­ties to what the An­cient Ro­mans used at their break­wa­ters and ma­rine ar­eas, at least in how it was formed. Davi­dovits guessed that the mix­ture was com­posed of clay, wa­ter, lime and crushed lime­stone mixed with a wa­ter slurry to form an al­ka­line sub­stance. He fur­ther con­sid­ered – and the bril­liant sim­plic­ity of the con­cept is what makes it even more log­i­cal – that the blocks were built and as­sem­bled in place and as they cured and so­lid­i­fied, they would press against one another and set­tle pre­cisely into place. It was a far sim­pler idea than hav­ing to en­sure the pre­ci­sion of cut­ting each in­di­vid­ual block to ex­act re­quire­ments. The joints be­tween the blocks would also nat­u­rally form from the press­ing to­gether of the edges of the blocks.

Fur­ther ev­i­dence has backed up the con­cept of blocks be­ing formed in place – or nearly in place.

Michel Bar­soum, a pro­fes­sor of ma­te­ri­als sci­ence and en­gi­neer­ing at Drexel Univer­sity in Philadel­phia, and Gilles Hug of the Na­tional Cen­ter for Sci­en­tific Re­search in France de­cided to in­ves­ti­gate Davi­dovits’ the­o­ries us­ing a mi­cro­scope, X-rays and chem­i­cal anal­y­sis of bits of stone from the pyra­mids. They dis­cov­ered that a small but sig­nif­i­cant per­cent­age of the blocks on the higher por­tions of the pyra­mids were in­deed cast from con­crete.

Bar­soum’s team fur­ther dis­cov­ered that while Davi­dovits was on the right track, there was one key dif­fer­ence in the Egyp­tian con­crete. Elec­tron-mi­cro­scope anal­y­sis showed that in­stead of or­di­nary clay, the mix- ture fea­tured Di­atoma­ceous earth as the “clay” com­po­nent. Its com­bi­na­tion of be­ing a soft sed­i­men­tary rock with em­bed­ded fos­silized re­mains of al­gae made it a far more ac­tive com­bi­na­tion dur­ing the cur­ing process. Also, like the ever-re­struc­tur­ing and hard­en­ing na­ture of the sea­side Ro­man con­crete, this type of ma­te­rial tended to re­set­tle, re­struc­ture and strengthen – rather than weaken – over time.

As for the build­ing process for the over­all pyra­mid, based on a com­bi­na­tion of what the team had ac­tu­ally seen of the real build­ing blocks and their own the­o­ries, Bar­soum and com­pany thought it could be log­i­cal that some cut stone blocks might have been used near the base, as a foun­da­tion of sorts. Then, as the con­struc­tion con­tin­ued to move farther up to the top and it be­came more chal­leng­ing to lift the stones to the higher lev­els (even with com­plex ramps), the con­struc­tion process shifted to a higher per­cent­age of poured con­crete.

The team an­a­lyzed this with con­sid­er­able sci­en­tific rigor, with photographic study, chem­i­cal anal­y­sis and mod­ern mi­cro­scopic and struc­tural ma­te­ri­als anal­y­sis to back up their stud­ies. Their re­sults pointed to pyra­mids where their lower sec­tions were likely formed from cut rock and the higher sec­tions made from geopoly­mer blocks that had been formed in place – or nearly in place.

One piece of ev­i­dence Bar­soum’s group found that sup­ports this the­ory came from an ex­am­i­na­tion of some of the pyra­mids’ build­ing blocks that ar­chae­ol­o­gists have re­ferred to as “back­ing blocks.” Th­ese were never in­tended to be seen by any­one and yet had pre­cise fea­tures that ap­peared to many like they had been pre­cisely cut. Why they would have been pre­cisely cut when that would have re­quired more work is a puz­zle, with the far more log­i­cal ex­pla­na­tion be­ing that they were sim­ply cast in place and the forms were pre­cise be­cause of hav­ing been molded in place.

A sec­ond ex­am­ple was in the places where the blocks were ir­reg­u­larly shaped rather than all be­ing pre­cisely cut – some­thing that oc­curred far more of­ten than the Hol­ly­wood ver­sions of all of this would have one be­lieve. In those places, if the blocks had sim­ply been cut to dif­fer­ent sizes and fit to­gether, not only would this have made the whole assem­bly process far more dif­fi­cult but it would also have re­sulted in gaps be­tween the blocks. Yet the struc­ture did not have any gaps. In­stead, the ir­reg­u­lar blocks were pre­cisely fit to­gether, ev­i­dence that sup­ports a “molded in place” con­cept where the blocks were pressed to­gether and the seams be­tween them nat­u­rally filled out.

A sci­en­tist who built fur­ther on both Davi­dovits’ and

Bar­soum’s work was Linn Hobbs, a pro­fes­sor of ma­te­ri­als sci­ence and en­gi­neer­ing at the Mas­sachusetts In­sti­tute of Tech­nol­ogy. Hobbs and his stu­dents wanted to bet­ter un­der­stand what kinds of con­crete mix­tures might have been avail­able to the con­struc­tion lead­ers of the time. Us­ing their un­der­stand­ing of what was nat­u­rally oc­cur­ring and do­ing some re­verse en­gi­neer­ing of their own, they hit upon one crit­i­cal new (ac­tu­ally, “old”) in­gre­di­ent that was def­i­nitely avail­able and used by the Egyp­tians of the time: na­tron salts.

Th­ese salts were read­ily avail­able to the an­cient Egyp­tians, formed nat­u­rally as salty lake beds evap­o­rated. The na­tron salts had one other fa­mous use: They were part of the mum­mi­fi­ca­tion process. They also be­come al­ka­line when ex­posed to wa­ter, which, in turn, made them an ex­cel­lent ac­ti­va­tion sub­stance for the geopoly­mer re­ac­tions. The fi­nal mix­ture that Hobbs and his team ended up re­dis­cov­er­ing was a geopoly­mer con­crete of na­tron salts, crushed lime­stone, kaoli­n­ite and sil­ica.

A log­i­cal next ques­tion is “Where did the Egyp­tians get their tech­nique for mak­ing con­crete that lasts thou­sands of years, along with all the other ad­vanced tech­nol­ogy that seems to have just ap­peared in a very short pe­riod of time?”

While much of the tech­nol­ogy likely came from Sumer, where hu­man civ­i­liza­tion first arose, the Egyp­tians them­selves may have left an an­swer to the big ques­tion of where their tech­nol­ogy ul­ti­mately came from.

In the Tem­ple of Horus, also known as the Tem­ple of Edfu, hi­ero­glyphs tell a fas­ci­nat­ing story that pro­vides im­por­tant clues to our true his­tory and helps ex­plains many of the anom­alies that ar­chae­ol­o­gists have tried to cover up.

Some of the in­scrip­tions in the tem­ple sug­gest that its lay-out was de­signed by a pre-dy­nas­tic group of peo­ple, known as the Shemsu Hor, the “Fol­low­ers of Horus”. The text also tells the same story of an an­cient ad­vanced civ­i­liza­tion as Plato’s story of At­lantis. Yet, main­stream Egyp­tol­o­gists have sup­pressed or ig­nored this vi­tal in­for­ma­tion and pre­sented a false nar­ra­tive not sup­ported by the ev­i­dence.

Could ad­vanced con­crete tech­nol­ogy in­deed been handed down by sur­vivors of a highly ad­vanced an­cient civ­i­liza­tion?

Sup­pres­sion of Our Real His­tory

Ro­man and Egyp­tian con­crete are just one ex­am­ple of how our his­tory has been lost or de­lib­er­ate ef­forts made to keep it con­cealed. Our mod­ern civ­i­liza­tion suf­fers be­cause of this loss of an­cient knowl­edge, but it doesn't all have to be lost.

In ad­di­tion to the Egyp­tians, the an­cient Sume­ri­ans left be­hind a vast writ­ten record of their own civ­i­liza­tion and the ear­li­est hu­man his­tory on clay cylin­ders. This record is of im­mense im­por­tance, and trans­lat­ing and study­ing it should be a very high pri­or­ity.

Yet of the more than 500,000 cylin­ders that have been dis­cov­ered so far, only a tiny per­cent­age have been trans­lated and ac­cess to the cylin­ders re­mains re­stricted. Some of them that have been trans­lated tell a fas­ci­nat­ing story that could trans­form mod­ern so­ci­ety – if only the in­for­ma­tion was more widely dis­sem­i­nated and ac­cepted.

The books of the Bible’s Old Tes­ta­ment are pre­dated by the Sume­rian texts. But most Chris­tians would rather be­lieve their dis­torted comic book ver­sion in­stead of the orig­i­nal, more ac­cu­rate and au­then­tic record.

It is the same with the more mod­ern New Tes­ta­ment. We now know that much of it was fab­ri­cated by the Ro­mans to hi­jack early Chris­tian­ity. We know this be­cause we now have au­then­tic texts used by the early Chris­tians – the very texts the Ro­mans sought to de­stroy be­cause they con­tra­dicted the new Ro­man ver­sion of Chris­tian­ity.

The texts were dis­cov­ered in 1945 by two Egyp­tian brothers while they were dig­ging for fer­til­izer around the Ja­bal al-ārif caves close to the Up­per Egyp­tian town of Nag Ham­madi. The texts con­sisted of 13 leather-bound papyrus codices buried in a large sealed clay jar. Be­ing Mus­lim, the brothers’ mother burned some of the texts and they were lost for­ever. What wasn’t burned was sold or given to a Cop­tic priest for safe-keep­ing. Even­tu­ally the texts made their way to Cairo and were seized by the gov­ern­ment. One book was sold out­side the coun­try and given to the fa­mous psy­chol­o­gist Carl Jung.

De­spite their im­por­tance, most of the texts were not trans­lated un­til the 1970s. The first trans­la­tion was pub­lished in 1977, but it was not un­til 1988 that the full trans­lated texts were made widely avail­able in English.

The Nag Ham­madi li­brary tells a much dif­fer­ent and cer­tainly more ac­cu­rate story of Je­sus and his time. One of the books claims to have been writ­ten by Je­sus him­self.

The texts in­clude many of those that the Ro­man church banned and sought to de­stroy be­cause they did not sup­port the Ro­man ver­sion of Chris­tian­ity, which was a sys­tem for so­cial con­trol – not the spir­i­tual and in­tel­lec­tual lib­er­a­tion that the real Je­sus taught.

To­day, most peo­ple call­ing them­selves Chris­tians have still not heard of the Nag Ham­madi li­brary and when in­formed of it show no in­ter­est in reading the au­then­tic new tes­ta­ment. They are happy to con­tinue their de­vout be­lief in a mythol­ogy that was in­vented by the Ro­man gov­ern­ment to un­der­mine the teach­ings of Je­sus.

As we reach the end of our mod­ern car­bon-fu­eled civ­i­liza­tion, it is high time that we dis­cover our true his­tory and learn from it. It is time for us to build a new civ­i­liza­tion based on in­tel­li­gent and sus­tain­able tech­nol­ogy and adopt a new way of think­ing about our­selves and our place in the world that is based on re­al­ity and not a mythol­ogy de­signed to keep us en­slaved in a cy­cle of self-de­struc­tion.

Colos­seum built by Ro­mans in 72-80 AD from con­crete. Photo by Kos­ala Ban­dara, CC

Hi­ero­glyphs at the Tem­ple of Edfu. Photo by Jerome Bon,

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