Joseph Davidovits posited that the blocks of the Great Pyramid are not carved stone but mostly a form of limestone concrete or man-made stone50
d’Histoire Naturelle in 3000 years later? Their in Egypt in the AswanParis, what would hap- answer was surprising: region! It was on thatpen if we buried in the the archaeologist would day that I realized thatground a piece of the analyze this object dis- if I did not reveal theproduct that we were interred from the gar- synthetic nature of thesynthesizing in the lab- den of a ruin in Saint- product we had devel-oratory at the time (our Quentin, and the analy- oped, it would be takenfirst geopolymer mate- sis would reveal that for natural stone.rial), and an archae- the nearest natural out-ologist discovered it crop of the stone wasT.D. Did you have to face any controversy or criticism from the scientificcommunity, while trying to establish your point?Dr. Davidovits I presented my ideas publication of my book wrote a startling reviewat several International for the general public, stating that I had falsi-Egyptology conferenc- (The pyramids: an enig- fied the scientific dataes: Grenoble, France ma solved, 1988, New (my chemical analysis),(1979), Toronto, Canada York), several materials etc. My friends want-(1982), Manchester, UK scientists sent me a let- ed me to go to court(1984), Cairo, Egypt ter in which they asked because of these insults.(1988). They generat- me to stop this research I answered: “No, this ised great debates, sev- because “I was jeop- part of the game in sci-eral articles in news- ardizing my career”. ence. A new theory ispapers, yet no hostil- In 1989, an eminent always severely chal-ity. However, after the American Egyptologist lenged. This has always 51
been the case in the any understanding of publicity among thepast, and remains true basic geologic prin- gullible and sensation-in our present time.” ciples and understood minded... The geopoly-One famous American the implications of sim- mer theory is defunct;geologist wrote a paper ple geological evidence we still remain in awe ofin 1992 that states: at Giza, he would have the enigma of Egyptian“... we feel it is the realized that this geo- skill and engineering.”duty of a profession- polymer theory has no Ironically, his study wasal geologist to expose basis in fact... We have made on stone sam-this egregiously absurd also shown how geolog- ples taken from naturalarcheological theory ic common sense can limestone that was partbefore it becomes part destroy archaeologi- of the bed-rock uponof entrenched pseudo- cal quackery, but not, which the pyramid wasscience... We believe unfortunately, before it constructed.that if Davidovits had has enjoyed widespreadT.D. There is an increasing trend in science and technology to go forgreener materials, and geopolymer is certainly an example of a sustain-able cement material. But are there any shortcomings? How well does itperform in comparison to conventional cement materials?Dr. Davidovits The only and major years ago (Portland years durability war-shortcoming is its nov- cement, 150 years ago). ranty, everybody shouldelty. It is too young. Since liability claims for understand that, as farGeopolymer cement construction materi- as the applications forwas invented only 30 als require at least 20 the construction indus- 52
try are concerned, thisis a major drawback.This explains why geo-polymer applicationswere first developed inother fields and nichemarkets, which do notrequire these types ofcodification. Geopolymer MouldsT.D. Volume change is the most detrimental property of cement, causingshrinkage which affects long-term strength and durability. Any suggestionsspecific to geopolymers, about how to overcome this problem? Dr. Davidovits bility of glasses and the to a silicate framework number of non-bridging generally increases To understand the oxygens (-Si-OH or -Si- durability. The impor-long-term durability O− Me+ groups). The tance of non-bridgingissues on geopolymers results of this study oxygens on glass dura-we may make a paral- reveal several points bility is that non-bridg-lel with glass technolo- that may be transferred ing oxygens providegies and science. It has to geopolymer struc- a point of attack onbeen recognized for a tures. One is that the a molecular scale forlong time that there is addition of aluminum protons or water mole-at least a rough correla-tion between the dura- 53
cules. Similarly in geo- chemical attack and with Al-OH or Si-O-Al-polymers, it is the high- offer long-term stabil- O-Si- species are pronely polymerized regions ity, whereas the less to shrinkage and leach-that are resistant to polymerized regions ability.T.D. In the context of durability of geopolymer materials, how well char-acterized are the gel pores, cement hydration and alkali-aggregate reac-tion? What improvements can we, the scientists, make in order to furtheroptimize the product? Dr. Davidovits the pH of the materi- Geopolymer Cements to Minimize Carbon- Pore solution analysis al and perform Nuclear dioxide Greenhouse-is worthwhile for mono- Warming. The dem-meric/dimeric gels like Magnetic Resonance onstration was clear.those found in Portland Geopolymer materi-cement or alkali-acti- spectrometry (NMR) for al does not generatevated slag for example. any deleterious alkali-It is not valid for the silicon (Si) and alumini- aggregate reaction.investigation of any fullycondensed geopolymer um (Al).matrix. It may be usedto show that geopo- As for alkali-aggregatelymerization, i.e. net-working of the frame- reaction, I publishedwork, is not complete.Instead of pore solution my first study on thisanalysis, we measure topic 20 years ago, in Ceramic Transactions, Vol. 37, (1993), Cement- Based Materials: Present, Future, and Environmental Aspects. pp 165-182, titled: 54
T.D. What do you consider to be some of the greatest challenges in thisfield of research? Dr. Davidovits ground to shift away This is not easy because To get those scien- from hydration-based it requires from themtists working in the field reasoning towards geo- that they go back toof geopolymer cement polymer terminology school.and who had a Portland and chemistry.cement chemistry back-T.D. What, in your opinion, are some of the emerging applications that willgain interest in the next few years?Dr. DavidovitsI always make a ization in the field of ate geopolymer cement pharmaceutical applica- type will provide theclear distinction tions, high-tech ceram- solution for mass pro- ics, paints and coat- duction worldwide (seebetween Geopolymer ings, and heat-resistant at www.geopolymer.org composite materials. As the News dated AugustTechnologies and for the cement field, I 2012 on “red geopoly- guess that the newly mer cement”).Geopolymer Cement discovered ferro-sial-applications. Withrespect to GeopolymerTechnologies, we shouldsee the commercial- 55
Balanced chemical equation showing geopolymer synthesis starting with metakaolin, MK-750 56
T.D. One North American geopolymer application is a blended Portland-geopolymer cement known as Pyrament® (patented in 1984) for rapidpavement repair. Shall we consider geopolymer as a supplementary orrather a complementary material to cements and concretes, or does itreally have the potential to replace the conventional Portland cements ona large scale? Dr. Davidovits and Johannesburg) but for the manufacture of the geological resourc- geopolymer cement.I once visited a cement es, namely limestone, Other regions in theplant in South Africa had to be extracted ca. world are experiencingand was struck by the 100 km up north and the same situation. Inlocal conditions rul- transported by train to other words, geopoly-ing the manufacture of the plant. On the other mer cement is a com-Portland cement there. hand, the local geology plementary material toThe plant was located was perfectly adapted Portland cement.very close to the market(the cities of PretoriaT.D. As a research scientist, I have worked on calcium phosphate cement(another sustainable cement material) derived from calcium silicate-basednatural minerals, but not having aluminium as a primary constituent.Would you classify this kind of material as a geopolymer? Dr. Davidovits Well, you should con- the presence of a poly- weight molecules. Thissider the geopolymeric meric network or, at is not the case for regu-terminology that implies least, of high molecular lar calcium phosphate 57
hydrates such as brush- ic acid, and wollaston- and binders are genu-ite, CaHPO4.2H2O, ite, CaSiO3. On the ine geopolymers, withwhich results from the other hand, aluminum high-macromolecularreaction of phosphor- phosphate cements networks.T.D. It seems that none of the potential applications has advanced beyondthe development stage (correct me if I am wrong), but the durability attri-butes of geopolymers make them attractive for use in high-cost, severe-environment applications such as bridges. Can you name a few industriesthat are actively producing geopolymers for construction?Dr. Davidovits Yes, there are several. & Industrial Research, to have achieved “theMost of them needed Jamshedpur, India. I ‘world first’ productionseveral years in R&D met with Dr. Kumar in run of geopolymer con-before being ready for 2005. The development crete”. It was undertak-commercialization and involved major compa- en in Canberra, involvingindustrialization. This is nies such as Tata Steel. the production of 3,000typical for any develop- They are planning to components, totalingment of new materials. have 10 commercial 2,500 tons. I had vis-For example, one million installations in India ited ROCLA in 1999.geopolymer pavement in the coming 5 years. In 2011, in Germany,bricks (roughly 3,000 An Australian compa- France and the UK, thetons) were manufac- ny ROCLA, one of the global chemical com-tured in 2012 in India pioneers in geopolymer pany BASF launched aunder the supervision of precast concrete for geopolymer joint groutDr. Sanjay Kumar from commercial production, named PCI-Geofug®.the Council of Scientific claimed in Dec. 2011 Another Australian com- 58
Prof. Joseph Davidovits visiting India in 2010, to expand research collaborationpany, Rockwool, a man- into briquettes. The the company made itufacturer of insulating briquettes of geopoly- public only in Decembermaterial, has found a mer material are fed 2011, 4 years later. Butway to capture, recy- back into the furnace you are right in statingcle and re-use tons of and made into fibers that no bridge has, sowaste generated from for Rockwool insulation. far, been built in geo-the manufacturing pro- The plant has been run- polymer concrete.cess, using a geopoly- ning this geopolymermer to bind the waste process since 2007, yet 59
T.D. I know you are very much active with a range of events in theGeopolymer Institute. Your institute regularly organizes tutorials, camps,conferences and so on, not to speak of the widespread research network-ing that you have established to date. Any upcoming events that you wouldlike to make us aware of?Dr. Davidovits My archaeological namely HBRC, Cairo, for the development ofresearch is attracting a the Egyptian Housing sustainable construc-lot of interest in some & Building National tion materials. We havedeveloping countries. Research Center. The a timing problem due toWe are presently pre- target is to transfer our the political situation inparing a partnership knowledge of ancient that country. We hopewith the major build- building materials (pyr- to be able to start ining institution in Egypt, amid stone and the like) the coming year. 60
T.D. As a lab instructor, recently I got a chance to introduce the topic ofgeopolymers and ceramics to an international group of students. Studentsmade their own geopolymer samples from fly-ash, prepared moulds andcharacterized them by FTIR using KBr pellets (for structural composition),by DSC of fresh mixture (to obtain heat of hydration), by Instron machineusing ASTM standards, after wet, dry and wet-dry processing (to measurecompressive strength) and so on. The student feedback was overwhelm-ing; they asked thought-provoking questions and became more and moreinterested. What message do you have for student researchers like them? Dr. Davidovits this was not followed them for regular build- by other engineers ing and civil engineer- Although geopolymer- and scientists involved ing operations, whereization does not rely on in the development of people are working withtoxic organic solvents geopolymeric systems. bare hands, is nonsense.but only on water, it Apparently, these sci- This could explain whyneeds strong alkalis entists never put their geopolymer cementsuch as sodium hydrox- finger into their reac- technology has notide (NaOH) that may be tion mixture, which reached mass applica-dangerous, and there- has a SiO2:Na2O ratio tions and remains con-fore requires some safe- of 0.20 or 0.60. The fined to high-tech nichety precautions. Because problem is that practi- markets. So my mes-I was a chemist, when I cally all papers dealing sage is: develop “user-started the research on with “alkali-activated” friendly” systems.geopolymers I decided cements describe reci-to select alkaline condi- pes that are not user-tions that could be clas- friendly. To recommendsified as “mild”, i.e. user-friendly. Unfortunately, 61
T.D. Any other aspect that you would like to address for the scientificreader community, something that may not have been covered in myquestionnaire?Dr. DavidovitsMy friend Dr.Waltraud Kriven fromIllinois Universityonce proclaimed:“Geopolymers, morethan just cement”.Indeed, when, in 1979,I introduced the geo-polymer concept andthe related terminol-ogy, I had no ideaabout cement. But inthe mind of cementscientists, geopolymeris only cement andtherefore they try tounderstand its materi-al properties with theirPortland cement back-ground, replacing cal-cium (Ca) with sodi- Dr. Tania Dey posed with her lab students during Instron compressive strength measurement ofum (Na), which is not geopolymer mouldsappropriate. To better 62
explain these chemical shift has not been well tists working on high-processes and the resul- accepted by practitio- tech ceramics and com-tant material properties ners in the field of alka- posites understand therequires a major shift in li-activated cements importance of the geo-perspective, away from who still tend to explain polymer terminologythe classical crystalline such reaction chemistry and use it with successhydration chemistry of in Portland cement ter- in numerous scientificconventional cement minology. On the other projects worldwide.chemistry. To date this hand, materials scien-T.D. Dr. Davidovits, many thanks for your time and for this insightful discus-sion. I hope the scientific community will greatly benefit from your work,thoughts, and suggestions. Interested readers may wish to go throughyour books and website (www.geopolymer.org) for further details.The author, Dr. Tania Dey, is a research scientist by profession. She earned her PhDin 2002 and since then has worked in the area of colloids, polymers, nanostructuresand advanced materials. Her work has been multi-disciplinary with diversified appli-cation potential. The author can be reached at: [email protected]: http://publicationslist.org/tania_dey 63
“Tactility is the sensibility of the skin as surface of contactbetween the perceiving subject and the perceived object.Proprioception folds tactility into the body, enveloping theskin’s contact with the external world in a dimension of medi-um depth: between epidermis and viscera.“Brian Massum www . ispectrummagazine . c o m 64
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