Is it really a geopolymer?

1. Abstract

Solid alkali silicate samples will be synthesized from (i) sand (ii) ground granite which will be obtained with the help from Trevor Hawke who has and can collect authentic samples from contacts and collectors from relevant regions in South America. Dr. Joseph Davidovits are also willing to send us some of their starting materials from Pumapunku for a more in-depth analysis and of their resulting product. The solid alkali silicates will be fabricated according to Marcel Foti’s repeatable procedure and their chemical and microstructural composition will be examined by state-of-the-art facilities in the (national resource) Center for Microanalysis of Materials. The sand may contain some amount of alumina or iron oxide, and its surface may expose reactive aluminum or iron chemical bonds which could enable aluminum tetrahedra to be reacted with the highly corrosive, alkaline solution. If the material is not geopolymer, its chemical composition, microstructure and some mechanical properties (compressive and flexure strengths and NDE properties) will be identified and measured. The team will consist of one Ph.D. student, Prof. Kriven and Trevor Hawke who will share his experience and help to acquire authentic starting materials and sample megaliths. The research duration will be one year and published.

2. Introduction

1. Current status of knowledge on geopolymers

Geopolymers (GPs) are a class of inorganic polymeric, X-ray amorphous materials consisting of alumina, silica, and alkali metal oxides. They are typically synthesized by mixing a a powdered aluminosilicate source (i.e. such as amorphous metakaolin or fly-ash) with amorphous silica dissolved in highly caustic alkaline (MOH) solutions, where M is an alkali cation.^1-12 Geopolymers can be produced over a wide range of chemical compositions, centered on the molar ratios of M₂O•Al₂O₃• xSiO₂•yH₂O, where M is an alkali metal cation (typically, Na⁺, K⁺, Cs⁺), x =2-6, and y = 7.5-13.^6,12 Fig. 1(a,b) locates this composition on Na₂O•Al₂O₃•SiO₂ and K₂O•Al₂O₃•SiO₂ phase diagrams. Geopolymers are inorganic polymers that undergo (i) dissolution of the aluminosilicate source, (ii) polycondensation and (iii) precipitation under ambient temperature. The reaction is mildly exothermic at ~65 °C.

Stoichiometric geopolymer can be fabricated as schematically shown in Fig. 2. When crystalline clay of composition (Al₂O₃•2SiO₂•2H₂O) is heated to 750°C for 2 hours it decomposes to amorphous metakaolin (Al₂O₃•2SiO₂) which is ideally in the form of a powder. “Water glass” or alkali metasilicate solution is highly caustic containing 1 M NaOH, KOH or CsOH dissolved in 10 M H₂O to which are added 2 M amorphous SiO₂ which dissolves completely forming a clear solution. The solution is highly viscous for Na metasilicate, but less viscous for K metasilicate and even less for Cs metasilicate solution. The amount of water varies depending on particle size and specific surface area of the aluminosilicate source (metakaolin). Too much water will lead to porosity in the resultant microstructure, so excess water is minimized. The 13 moles of water were found to be optimal for BASF metakaolin of particle size 1.2 mm to mix with Na₂O•2SiO₂ to form Na₂O•2SiO₂•13H₂O waterglass. The powder and liquid are mixed under high shear, poured into a plastic mold, covered so as to avoid water loss, and left to set for 24 hours at room temperature, or shorter times at higher temperatures up to 50°C or even 80 °C.

It is important to note that kaolinite containing a minor amount of iron oxide can also behave in a similar manner to alumina forming a solid solution. Therefore, if there is insufficient aluminum in the clay, solid solution with iron oxide is also able to produce an Al₂O₃-Fe₂O₃ solid solution-based geopolymer.¹⁴

Fig. 1(a) “System Na₂O-Al₂O₃-SiO₂; composite,” E. F. Osborn and A. Muan, revised and redrawn, “Phase Equilibrium Diagrams of Oxide Systems,” Plate 4, published by the American Ceramic Society and the Edward Orton, Jr., Ceramic Foundation, 1960.

Fig. 1(b) “System K₂O-Al₂O₃-SiO₂; composite,” E. F. Osborn and A. Muan, revised and redrawn Phase Equilibrium Diagrams of Oxide Systems, Plate 5, published by the American Ceramic Society and the Edward Orton, Jr., Ceramic Foundation, 1960.

Fig. 2. Schematic illustration of the synthesis of geopolymer from an amorphous aluminosilicate powder and highly caustic alkali metasilicate solution.

2. Formation of geopolymer

The essence of the geopolymerization reaction is due to the highly strained AlO₅^2- coordination polyhedra in the amorphous metakaolin which forms a double bond with one Al atom and which is then susceptible to dissolution by the highly caustic, alkali metasilicate solution (“water glass”) of standard composition e.g. Na₂O•2SiO₂•11H₂O.¹² The amorphous aluminosilicate source is susceptible to dissolution in the highly alkaline solution where the Al³⁺ then forms AlO₄^- tetrahedra. These attract charge-balancing Group I cations and react with SiO₂ tetrahedra to form an amorphous 3D network (Fig. 3). The dissolution is the rate-determining step.

Fig. 3. Dissolution of the aluminosilicate source (e.g. metakaolin, Al₂O₃•2SiO₂•2H₂O) is due to dehydration of crystalline kaolinite (a) where the Al³⁺ is in 6-fold octahedral coordination, to decompose into amorphous metakaolin (b) where a highly strained 5-fold coordinated Al³⁺ polyhedron forms a double bond with oxygen. Upon dissolution in waterglass a regular AlO₄^- tetrahehedron (c) springs into existence and is ready to polymerize with silicate tetrahedra.

3. Atomic structure and microstructure of geopolymers

The amorphous atomic structure contains SiO₂ and AlO₄^- corner-shared, tetrahedral units which are formed at room temperature (Fig. 4). The microstructure of geopolymers is nanoparticulate (~20-40 nm in diameter, (Fig. 5)) and nanoporous (~6.8 nm in diameter, ~40 % by vol (Fig. 6). Despite the nanoporosity, geopolymer is impermeable. Figs. 5 and 6 are SEM and TEM micrographs of K-based geopolymer, respectively, showing the nano-particulate nature of the aluminosilicate, which on a macroscopic level is impervious and structurally robust when reinforced.

Fig. 4. Currently accepted atomic model of geopolymer structure.⁵

Fig. 5. High resolution transmission electron microscopy of GP precipitates.^8,12The precipitate diameter sizes are 20 nm (Na GP), 30 nm (K GP) and 40 nm (Cs GP)

Fig. 6. High angle annular dark field TEM (HAADF) micrograph of KGP showing nanoporosity.¹² The white regions are the aluminosilicate nanoparticles.

In addition to geopolymers made by charge balancing with aqueous Group I alkali solutions, our recent work has demonstrated that aluminosilicate- based geopolymers can be charge balanced with some organic molecules, such as guanidine or guanidinium hydroxide which produces a highly caustic pH of 14 when dissolved in water.^15-17 Guanidine is related to guanine, a component of biological DNA. This study demonstrates that geopolymers could be made using guanidine rather than sodium hydroxide, and hence organic bases in general may be alternatives to alkali hydroxides in geopolymer synthesis. This work is relevant to other non-sodium containing potential geopolymer composites identified in South America. The guanidine-based materials were structurally similar to sodium-based geopolymers but not identical.

In the presence of calcium such as in slag, a mixture of geopolymer and cement is made, since our Ph.D. study on this topic has shown that first calcium silicate hydrate (C-S-H) is formed and when the amount of calcium is reacted, geopolymer is also able to form as an intimate mixture of cement and geopolymer “mortar”.^18-20

Researchers led by Joseph Daviovits in Pumapunku-Tiwanakum, Bolivia, found, in addition to ancient geopolymer sandstone-concrete megalithic slabs, puzzling “H” structures made of andesitic volcanic stone.^21-22 They carried out a microstructural SEM study of the gray andesite shows the presence of organic matter viz., carbon, nitrogen, and minerals containing Na, Mg, Al, Si, P, S, Cl, K, Ca. Organic matter is very unusual, if not impossible in a solid volcanic stone and suggests ceramic-like man-made stone. Their research demonstrated that these architectural components manufactured 1400 years ago (ca. CE 600) were fashioned with a type of organo-mineral precursor.

Prof. Kriven is also in contact with Mr. Trevor Hawke of the Harmonic Research Group, CA who is keenly interested in the role of geopolymers in ancient megalithic structures of South America and Mexico. Based on his research of samples therefrom, he has prepared two 60 page papers on his findings of authentic archeological samples as studied by SEM and EDS.^23,24 Trevor Hawke has developed a formulation and procedure for making geopolymer pastes as could have been used in ancient times to make such geopolymer composites, which he has shared with Kriven. He is willing to collaborate with Prof. Kriven in a more in-depth study of megalithic samples from South America and Mexico. He currently has, or is able to, collect for us, authentic samples of such megaliths from contacts and collectors with whom he is in contact, which he is prepared to send to Prof. Kriven.

Relevant videos

There are relevant videos pointing to the observation of possibly geopolymer-derived interlocking blocks or megaliths in ancient structures built by, for example a possible, pre-Inca civilization in Peru, and in other places in South America, such as Puma Punku (Andes), Ollantaytambo (Andes) Sacsayhuaman, Across Cusco, and dating back to possibly 15,000 BC, as well as in the Aswan Quarry (Egypt). Pre-Inca Geopolymer Explains the Massive Megaliths https://share.google/yk7WgomOLnItcj7v2

Hypotheses

Based on our understanding of geopolymers resulting from the past 26 years of research on geopolymers resulting in 120 journal publications and editing of 20 conference proceedings books, we propose to carry out the experiments demonstrated by Marcel Foti as described in his book “Natron Theory” and in the video https://www.youtube.com/watch?v=v1qf9QbWbP8.

Hypothesis 1:

We plan to synthesize waterglass samples according to Marcel Foti’s recipe but made from (i) sand and (ii) ground granite obtained from relevant regions in South America. They will be ball milled and sieved to size ranges of less than 44 microns, 500 microns and 1 mm. It is anticipated that the smaller particle sizes will be fully dissolved and the larger particle sizes might be partially unreacted. The solid alkali silicate will be fabricated according to Marcel Foti’s repeatable procedure and then we propose to examine them to understand exactly what inorganic material was produced at each stage of the iterative procedure.

Prof. Kriven is in contact with Mr. Trevor Hawke of the Harmonic Research Group, CA who is keenly interested in the role of geopolymers in ancient megalithic structures of South America and Mexico. Based on his research of samples therefrom, he has published one 61 page paper, and is preparing another large, 60 page paper on his findings of authentic archeological samples as studied by SEM and EDS.^23,24 Trevor Hawke has developed a formulation and procedure for making geopolymer pastes as could have been used in ancient times to make such geopolymer composites, which he has shared with Kriven, and is willing to collaborate with Prof. Kriven in a more in-depth study of megalithic samples from South America and Mexico. He currently has, or is able to, collect for us authentic samples of such megaliths from contacts and collectors with whom he is in contact.

It is planned to import the sand from one or more locations in South America, such as Puma Punku (Andes), Ollantaytambo (Andes) Sacsayhuaman, Across Cusco. Enquiries will be made from the appropriate government officials through the help of Trevor Hawke and Prof. Kriven’s former post-doctoral researcher and now colleague, Prof. Ana Trindade who is located at:

Dra. Ana Carolina Constâncio Trindade
Departamento de Engenharia de Biossistemas
Laboratório de Construções Rurais e Ambiência
Núcleo de Pesquisa em Materiais para Biossistemas (BioSMat)
Universidade de São Paulo (USP), campus Pirassununga
Phone (BR): (+55) (24) 98812-3719
E-mail: anatrindade@usp.br
Department of Biosystems Engineering
Rural Constructions and Ambience Laboratory
Research Center for Materials for Biosystems (BioSMat)
University of São Paulo (USP), Pirassununga campus

We plan to synthesize samples according to made from (i) sand and/or (ii) granite obtained from South America. We will examine their chemical compositions and microstructure to see if they match the aluminosilicate geopolymers having nominal compositions of: (Na₂O/K₂O)•(Al₂O₃/Fe₂O₃) •4SiO₂•xH₂O, with or without the co-existence of calcium silicate hydrate (C-S-H) sodium aluminosilicate hydrate (N-A-S-H) or potassium silicate hydrate (K-A-S-H) cementitious mortar species.

We will use the extensive state-of-the-art facilities housed in the Center for Microanalysis of Materials on the campus of the University of Illinois at Urbana-Champaign UIUC). This is a US National Resource Center which has been funded in the past at $4 million per year. In addition, we will have access to the complementary state of the art facilities housed in the Chemistry Department at UIUC as well as the relevant facilities in the research laboratory of Professor Kriven in the Department of Materials Science and Engineering at UIUC.

Relevant equipment include:

Optical microscopy in transmitted, unpolarized and polarized light capable of heating to 1500°C
X-ray diffraction including Rietveld analysis
Thermogravimetric analysis
Differential scanning calorimetry
Scanning electron microscopy (EDS) and Energy Dispersive Electron Microscopy (EDS)
Transmission Electron Microscopy and EDS (RT and hot stage TEM)
High resolution scanning and transmission electron microscopy (STEM)
X-ray fluorescence (XRF)
Inductively coupled plasma (ICP)
Nuclear magnetic resonance (NMR)
BET surface area measurements
Porosimetry and density measurements

Hypothesis 2:

Based on our measurements of the chemical and microstructural composition of the solid waterglass produced of modulus 2, 3 and possibly 4, we will examine the composition and in particular, the aluminum and calcium content present and determine if the composition corresponds to conventional geopolymer. In particular, we will focus on how much aluminum is present in the sand added as well as in the resulting solid waterglass. It is hypothesized that the sand is not pure silica but may contain some amount of alumina or iron oxide, and if they as at the surface of the sand it may expose reactive aluminum or iron chemical bonds which could enable aluminum tetrahedra to be reacted with by the highly corrosive, alkaline solution.

The presence of calcium in the sand or granite will indicate whether a mixture of geopolymer and cement was made, since our Ph.D. study on this topic has shown that first calcium silicate hydrate (C-S-H) is formed and when the amount of calcium is reacted, geopolymer is also able to form as an intimate mixture of cement and geopolymer “mortar”.^18-20 We will try to obtain samples of geopolymer-hypothesized, megaliths from South America and examine their chemical compositions and microstructure to see if they match the aluminosilicate geopolymers having nominal compositions: (Na₂O/K₂O)•(Al₂O₃/Fe₂O₃)•4SiO₂•xH₂O.

Hypothesis 3:

If possible other origins of sand or granite will be obtained with the assistance of Trevor Hawke by requesting them from relevant regions in South America or Egypt. For example, our colleagues, Dr. Joseph Davidovits Ralph Davidovits are willing to send us some of their starting materials for a more in-depth analysis of starting sand from the Pumapunku-Tiwanakum region in Bolivia.

3. Methods

Participants/Sample

1. We plan to synthesize samples made from (i) sand and/or (ii) granite samples obtained from South America. We will examine their chemical compositions and microstructure to see if they match the aluminosilicate geopolymers having nominal compositions of : (Na₂O/K₂O)•(Al₂O₃/Fe₂O₃) •4SiO₂•xH₂O, with or without the co-existence of calcium silicate hydrate (C-S-H) sodium aluminosilicate hydrate (N-A-S-H) or potassium silicate hydrate (K-A-S-H) cementitious mortar species.

2. If possible other origins of sand or granite will be obtained by requesting them from relevant regions in South America or Egypt, as guided by Trevor Hawke and his contacts.. In addition, our colleagues, Dr. Joseph Davidovits and Ralph Davidovits are willing to send us some of their starting materials for a more in-depth analysis of starting sand from the Pumapunku-Tiwanakum region in Bolivia.

Materials and Procedures

For this we will use the extensive state-of-the-art facilities housed in the Center for Microanalysis of Materials on the campus of the University of Illinois at Urbana-Champaign UIUC). This is a US National Resource Center which has been funded in the past at $4 million per year. In addition, we will have access to the complementary state of the art facilities housed in the Chemistry Department at UIUC as well as the relevant facilities in the research laboratory of Professor Kriven in the Department of Materials Science and Engineering at UIUC.

Relevant equipment include:

Optical microscopy in transmitted, unpolarized and polarized light capable of heating to 1500°C
X-ray diffraction including Rietveld analysis
Thermogravimetric analysis
Differential scanning calorimetry
Scanning electron microscopy (EDS) and Energy Dispersive Electron Microscopy (EDS)
Transmission Electron Microscopy and EDS (RT and hot stage TEM)
High resolution scanning and transmission electron microscopy (STEM)
X-ray fluorescence (XRF)
Inductively coupled plasma (ICP)
Nuclear magnetic resonance (NMR)
BET surface area measurements
Porosimetry and density measurements

Planned Analyses

We will use the extensive state-of-the-art facilities housed in the Center for Microanalysis of Materials on the campus of the University of Illinois at Urbana-Champaign UIUC). This is a US National Resource Center which has been funded in the past at $4 million per year. In addition, we will have access to the complementary state of the art facilities housed in the Chemistry Department at UIUC as well as the relevant facilities in the research laboratory of Professor Kriven in the Department of Materials Science and Engineering at UIUC.

Relevant equipment include:

Optical microscopy in transmitted, unpolarized and polarized light capable of heating to 1500°C
X-ray diffraction including Rietveld analysis
Thermogravimetric analysis
Differential scanning calorimetry
Scanning electron microscopy (EDS) and Energy Dispersive Electron Microscopy (EDS)
Transmission Electron Microscopy and EDS (RT and hot stage TEM)
High resolution scanning and transmission electron microscopy (STEM)
X-ray fluorescence (XRF)
Inductively coupled plasma (ICP)
Nuclear magnetic resonance (NMR)
BET surface area measurements
Porosimetry and density measurements

Ethics and Data Management

The research will be carried out in our usual manner of respecting the scientific truth and fairness to all researchers. The data will be published in suitable journals such as the Journal of the American Ceramic Society, or Ceramics International, or archeometry journals, as appropriate.

4. Pilot Data (Optional)

Our understanding of geopolymers is based on our past 26 years of research on geopolymers resulting in 120 journal publications. In addition, Prof. Kriven has edited of 20 conference proceedings books from the 23 International Symposia on Geopolymers which she has organized since 2023 as part of the International Conference and Exposition on Advanced Ceramics and Composites as part of the American Ceramic Society Engineering Ceramics Division and is held in January each year at Daytona Beach, FL, USA. In addition, Prof. Kriven has served on the organizing committee for the past four bi- or tri- annual Engineering Conferences International (ECI) conferences on Geopolymers held in Europe. Prof. Kriven has also served as organizer for geopolymer symposia in the Pacific Rim (Pacrim) countries for over the past decade, as part of her active work within the American Ceramic Society.

For this work we propose to carry out the experiments demonstrated by Marcel Foti as described in his book “Natron Theory” and in the video https://www.youtube.com/watch?v=v1qf9QbWbP8.

5. Budget

A detailed budget for one year can be provided to cover the cost of one, third year, post qualification exam, Ph.D. student, (12 months GRA plus fringe: $42,048) plus 0. 5 months of summer salary for Prof. Kriven as the Principal Investigator (0.50 months plus fringe: $16,420) to supervise this work as well as to carry out detailed TEM/STEM experiments on samples. Travel to present the work at the Annual International Symposium on Geopolymers which is held each year in Florida in January, for an estimated $2,000 will also be requested. Costs associated with shipping and acquiring samples may also be involved. The budget will need to cover the cost of equipment usage fees in the MRL and Chemistry Department on the UIUC campus. The detailed cost for use of each facility is available on the MRL website at https://mrl.illinois.edu/facilities/usage-rates. The exact usage will depend on the direction that the research will take. The total cost will be capped at $100,000.

6. References

1. J. Davidovits, “Mineral Polymers and Methods of Making Them”; U.S. Patent 4,349,386, September 14, (1982).

2. J. Davidovits, “Geopolymers - Inorganic Polymeric New Materials,” J. Therm. Anal. 37 1633-56 (1991).

3. J. Davidovits, “Geopolymer Chemistry and Properties”; pp.25-48 in Geopolymer’88 First European Conference on Soft Mineralogy, Vol.1 Edited by J. Davidovits and J. Orlinski. Geopolymer Institute and Technical University, Compiegne, France, (1988).

4. J. Davidovits, Geopolymer Chemistry and Applications, 4^th Edition (2015), published by the Geopolymer Institute, St. Quentin, France.

5. V. F. F. Barbosa, and K. J. D. MacKenzie, “Synthesis and Thermal Behaviour of Potassium Sialate Geopolymers,” Materials Letters, 57, 1477–82 (2003).

6. W. M. Kriven, J. L. Bell and M. Gordon, “Microstructure and Microchemistry of Fully-Reacted Geopolymers and Geopolymer Matrix Composites,” Ceramic Transactions vol. 153, 227-250 (2003).

7. P. Duxson, J. L. Provis, G. C. Lukey, S. W. Mallicoat, W. M. Kriven and J. S. J. van Deventer, “Understanding the Relationship between Geopolymer Composition, Microstructure and Mechanical Properties,” Colloids and Surfaces A – Physicochemical and Engineering Aspects 269 [1-3] 47-58 (2005).

8. W. M. Kriven, J. L. Bell, S. W. Mallicoat and M. Gordon, “Intrinsic Microstructure and Properties of Metakaolin-Based Geopolymers,” Proc. Int. Workshop on Geopolymer Binders – Interdependence of Composition, Structure and Properties, Weimar, Germany. Published by the Geopolymer Institute, St. Quentin, France 71-86 (2007).

9. J. L. Bell, P. Sarin, J. L. Provis, R. P. Haggerty, P. E. Driemeyer, P. J. Chupas, J. S. J. van Deventer and W. M. Kriven, “Atomic Structure of a Cesium Aluminosilicate Geopolymer: A Pair Distribution Function Study,” Chemistry of Materials, 20 [14] 4768-4776 (2008).

10. J. L. Bell, P. Sarin, P. E. Driemeyer, R. P. Haggerty, P. J. Chupas and W. M. Kriven, “X-ray Pair Distribution Function Analysis of Potassium Based Geopolymer,” J. Materials Chemistry, 18 [48], 5974 - 5981 (2008).

11. W. M. Kriven, “Inorganic Polysialates or “Geopolymers,” American Ceramic Society Bulletin, 89 [4] 31-34 (2010).

12. Waltraud M. Kriven (2018) 5.9 “Geopolymer-Based Composites”. In: Beaumont, P.W.R. and Zweben, C.H. (eds.), Comprehensive Composite Materials II. vol. 5, pp. 269–280. Oxford: Academic Press. https://doi.org/10.1016/B978-0-12-803581-8.09995-1

13. Kriven, Waltraud M. (2021) “Geopolymers and Geopolymer-Derived Composites”. In: Pomeroy, M. (ed) Encyclopedia of Materials: Technical Ceramics and Glasses, vol. 1, pp. 424–438. Oxford: Elsevier. http://dx.doi.org/10.1016/B978-0-12-818542-1.00100-4

14. “Formation of an Iron-Based Geopolymer Analogue,” J. L. Bell and W. M. Kriven, Cer. Eng. and Sci. Proceedings Vol 30, issue 2, pp 301-312. “Mechanical Properties and Performance of Engineering Ceramics and Composites IV. Edited by Dileep Singh and Waltraud M. Kriven, Ceramic Engineering and Science Proceedings, Vol 30, issue [2] 301-312 (2009).

15. “Geopolymers Made Using Organic Bases. Part I: Synthesis and Atomic Structure,” Devon Samuel and Waltraud M. Kriven. J. Am. Ceram. Soc., 107 [10] 6619-6635 (2024). https://doi.org/10.1111/jace.19754).

16. “Geopolymers made using Organic Bases. Part II: Crystallization and Physical Properties” by Devon M. Samuel and Waltraud M. Kriven. J. American Ceramic Society 107 [10] 6619-6635 (2024). https://doi.org/10.1111/jace.19971

17. “Geopolymers made using Organic Bases. Part III: Cast Magnesium, Yttrium, and Zinc Aluminosilicate and Silicate Ceramics,” Devon M. Samuel and Waltraud M. Kriven. J. Am. Ceram. Soc., 108 [2] pp (2024) https://doi.org/10.1111/jace.20149.

18. “Sodium Silicate Activated Slag - Fly Ash Binders: Part I – Processing, Microstructure and Mechanical Properties,” Kaushik Sankar, Peter Stynoski, Ghassan K. Al-Chaar and Waltraud M. Kriven, J. Am. Ceram. Soc., 101 [6] 2228-2244 (2017). https://doi.org/10.1111/jace.15391

19. “Slag-Fly Ash and Slag-Metakaolin Binders: Part II – Properties of Precursors and NMR Study of Poorly-Ordered Phases”, Kaushik Sankar, Andre Sutrisno and Waltraud M. Kriven, J. Am. Ceram. Soc., 102 3204-3227 (2019). https://doi.org/10.1111/jace.16224.

20. “Sodium Silicate Activated Slag - Fly Ash Binders: Part III – Composition of Soft Gel and Calorimetry,” Kaushik Sankar, Peter Stynoski and Waltraud M. Kriven, J. Am. Ceram. Soc., 102 3175-3190 (2019). https://doi.org/10.1111/jace.16219.

21. “Ancient Geopolymer in South American Monument. SEM and Petrographic Evidence,” Joseph Davidovits, Luis Huaman, and Ralph Davidovits. Materials Letters 235 120-124 (2019). https://doi.org/10.1016/j.matlet.2018.10.033

22. “Ancient Organo-mineral Geopolymer in South American Monuments: Organic Matter in Andesite Stone. SEM and Petrographic Evidence Joseph Davidovits, Luis Huamanb, Ralph Davidovits. Ceramics International 45 (2019) 7385–7389 https://doi.org/10.1016/j.ceramint.2019.01.024

23. “Evidence for Geopolymer Concrete in Megalithic Architecture of Cusco, Peru,” Trevor Hawke, Harmonic Research Group, San Diego, CA. almost ready for submission (April 2026). Email: harmonicresearchgroup@gmail.com

24. “Prehistoric Artifacts of Mesoamerica, Anthropological Evidence of ET Paleocontact,” Trevor Hawke, Harmonic Research Group, San Diego, CA. Aztlan Artifact Report pp 1-60, (May 2026). Email: harmonicresearchgroup@gmail.com

Is it really a geopolymer?

Is it really a geopolymer?

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