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Ancient geopolymer in south-American monument. SEM and petrographic evidence



The make-up of the sandstone megalithic blocks, weighing between 130 and 180 tonnes each, from Pumapunku -Tiwanaku, Bolivia, was compared with three geological sandstone sites from the area. The SEM/EDS, XRD and thin section results suggest that the sandstone megalithic blocks consist of sandstone grains from the Kalla-Marka geological site, cemented with an amorphous ferro-sialate geopolymer matrix formed by human intervention, by the addition of extra alkaline salt (natron) from the Laguna Cachi in the Altiplano, Bolivia. A detailed presentation of the research with SEM/XRD/Thin sections data is now available at <>
Geopolymer in South-
American monuments:
first scientific paper
28 Oct 2018
At the Geopolymer Camp 2018, in the Session:
Ancient Technologies, Prof. J. Davidovits presented
the first results of the joint research program
conducted by the Geopolymer Institute and
Universidad Catolica San Pablo, Arequipa, Peru, on
Tiahuanaco / Pumapunku megalithic monuments
(Tiwanaku), Bolivia (Lake Titicaca). See a brief
summary of the lecture in Davidovits’ Keynote
“State of the R&D 2018”, last 7 minutes of the video
at GPCAMP-2018.
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Latest articles
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28 Oct 2018
Tiwanaku Gate of the Sun and Pumapunku
megalithic geopolymer sandstone slabs.
The platform on top of the 4 step pyramid of
Pumapunku consists of 4 megalithic red sandstone
slabs, weighing between 130 and 180 tonnes each,
the largest among the New World monuments. Our
study suggests that the slabs are a type of
sandstone geopolymer concrete cast on the spot. It
was recently published in
Material Letters
(2019) 120-124, Online on 8 October 2018,
access with the following link: Materials Letters.
A second scientific paper dealing with the
spectacular stone artifacts made of andesite
geopolymer stone (H sculptures and the like) is
Roman cement
15 Jul 2018
Camp and
16 Feb 2018
new way
15 Dec 2017
Theory to
a world-
14 Dec 2017
are NOT
27 Jul 2017
presently under review. This study is linked to our
research carried out 36 years ago (in the 1980s)
titled “
Making Cements with plant extracts
” and
available for free download in our Library,
Archaeological paper #C at library/archaeological-
Archaeology Civilization News
antiquity concrete geopolymer stone
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... Recently, Davidovits developed research characterizing the material present in ancient monuments of pre-Columbian civilizations in South America, concluding that they were alkali-activated materials [11]. The studies carried out between 2016 and 2019 in the Tiahuanaco monuments (Tiwanaku/Pumapunku), Bolivia, and other monuments in Peru complement the studies carried out in the 70s and 80s and prove the durability of alkali-activated materials [12]. ...
... Bibliographic history of some important discoveries about activated alkali materials. Source[6]-[12]: ...
Full-text available
The Alkali-Activated Materials (AAM) are defined as materials obtained through the reaction between precursors and activators, and are separated into two classes depending on the products formed in the reaction, those rich in calcium, as the blast furnace slag, whose Ca/(Si+Al) ratio is higher than 1; and poor in calcium, which is the geopolymers subclass. In this review article, some bibliographical aspects were discussed regarding the discovery of these materials, through research conducted by Victor Glukhovsky and through the characterization of historical monuments by Davidovits, which began in the 50s and 60s and persist to the present day. The main products obtained in the alkaline activation reaction were also addressed, using the definition of polysialates and zeolites, in the case of geopolymers, and the tobermorite structure, in the case of materials rich in calcium. The main steps of the alkali-activated reaction, such as dissolution, condensation, polycondensation, crystallization, and hardening, were discussed. Some techniques for characterizing the AA reaction products were also examined, such as X-ray diffraction (XRD), nuclear magnetic resonance spectrometry (NMR), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). Finally, the main factors that interfere in the kinetics of AA reactions were explored, in which the type of cure and the activating solution used in the alkali-activated materials production stands out.
... The binder composition of GPC is alumino-silica source as precursor materials which are activated by alkaline activators [11] . Use of GPC as an alternate to conventional cement concrete thus reduces 80% of carbon emission [12] . The precursor materials employed for the production of GPC are mostly industrial wastes. ...
Geopolymer concrete (GPC) is a sustainable construction material developed from industrial waste products which eliminates the use of cement. Recycling the concrete waste for the development of GPC can satisfy the goals of this sustainable development. Appropriate trials were performed to accomplish a perfect blend of the binder, alkali activator (AA), alkaline liquid to binder ratio and aggregates to develop the GPC. Three types of curing methods namely ambient, sunlight and oven were used for the development of the GPC mixes. This investigation focuses on the assessment of mechanical properties and the microstructure characterization of GPC developed with Natural and Recycled Concrete Aggregates. Fly ash-ground granulated blast furnace slag (FA-GGBS) based recycled concrete aggregate (RCA) blended GPC achieves similar strength to that of GPC blended with Natural coarse aggregate (CA) but with marginal differences. Among all the types of curing, heat cured specimens show higher strength. It is observed that temperature influences the development of early strength gain of GPC with both Natural and Recycled Concrete Aggregate. Increase in AA ratio decreases the workability and increases the strength of GPC mixes. GPC specimens with AA ratio of 1:5 that were cured under ambient condition exhibited minimal strength while GPC mixes with AA ratio of 2.5, showed maximum strength under oven curing condition.
... The transformation of these industrial wastes into products for structural and/or engineering applications has been explored. Geopolymers produced from slag have been reported as one of the most promising sustainable building materials of the 21st century [28,29]. ...
Full-text available
The search for sustainable materials has grown globally due to the struggle against environmental impacts. From the recycling of PET packaging and the use of steel mill slag residue, from the steel production, it was developed in this work composites of PET matrix with additions of geopolymer obtained from steel mill slag. The compos- ites were produced with concentrations of 0, 20, 40, and 60% of geopolymer and were characterized by XRD, FTIR, TGA, DSC, and SEM. The XRD analyses indicated the presence of mineral constituents referring to the geopolymer in the composites. Through the thermal analyses, it was observed that the addition of geopolymer promoted the increase in thermal stability, besides increasing the crystallinity in concentrations of 40 and 60% of geopolymer. From the micrographs, it was observed that the addition of reinforcement changed the morphology of the material, promoting an increase in the porosity of the material. From the characterizations, it is possible to state that the addition of geopolymers in the PET matrix produces low-cost composites with good properties and can be used in engineering applications
... A conversão desses resíduos industriais em produtos úteis à sociedade tem sido muito explorada. Geopolímeros produzidos a partir de escórias têm sido reportados como um dos materiais sustentáveis de construção civil mais promissores do século XXI [3][4]. ...
Full-text available
Production of composites based on derivative products of industrial wastes was presented in this study, which aggregate value to metallurgical, steelmaker wastes of the industries, and this is reversed in beneficial effects to society. Geopolymeric materials can be a solution to industrial residues generated for these sectors. The objective of study was the investigation between a solid/liquid relationship to production of specimens obtained from geopolymerization reaction, using steelmaking slags by process of Linz Donawitz (LD) and ladle furnace (LF), respectively. Samples of the residues were synthesized from an alkaline solution of 8M potassium hydroxide (KOH) in the 1.2, 1.4 and 1.6 g/v proportions (solid/liquid). Analyses of chemical composition, thermal stability, microstructure, amount of crystallinity phases and porosity were evaluated to XRF, FTIR, TGA, SEM-FEG and Archimedes’ principle obtained by reaction geopolymerization through the steelmaking slags (LF and LD), respectively. The results indicated that obtained geopolymers from steelmaking slags developed specimens with dimensional stability and high possibilities of applications, as engineering materials. The results indicate that the solid / liquid ratio is an important point in the geopolymerization process, since the 1.6 samples presented a more cohesive appearance and higher densification values than the 1.2 and 1.4 samples.
Ultra high performance concrete (UHPC) is a cement-based material with great development prospects. However, the production of cement will produce a large amount of CO2, which does not conform to the current global trend of energy conservation and emission reduction, and limits the further development of UHPC. One of the ways to further develop UHPC is to reduce the carbon emissions in the production process of UHPC. The aim of this study is to develop a low-carbon alkali activated slag based Ultra-High Performance Concrete (A-UHPC) with ultra-low moisture content. Firstly, based on the particle dense packing model, an optimized combination of low-carbon cementitious mixture and aggregates skeleton is designed. Then, the effects of moisture content on the macro-properties, hydration mechanism and micro-mechanism of the developed A-UHPC are studied. The experimental results show that the fresh performance and macroscopic mechanical properties of A-UHPC are advanced at low moisture content. When the water-binder ratio is 0.29, the compressive strength at 28 d is the highest, reaching 118 MPa. Besides, low moisture content A-UHPC also shows good microscopic properties: its hydration degree can reach 62.58% and the longest molecular chain length of the polymer is about 4.74. In general, the developed A-UHPC can meet the requirement of high performance and low CO2 emission simultaneously, which could be one of the most suitable choices to achieve the goal of “Carbon peak and Carbon neutral” in the near future.
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The project, financially supported by the Regione Marche (POR Marche FSE 2014/2020), was assigned to the Ph.D. student Roberto Ercoli (UNIURB) with the supervision of Prof. Alberto Renzulli (UNIURB) and Prof. Eleonora Paris (UNICAM). Several universities and research groups such as the University of Urbino, University of Camerino, Institute of Geosciences and Georesources (IGG-CNR, Florence), University of Florence, Technical University of Liberec, and Warsaw University of Technology collaborated to create a European network working in this innovative and brand-new field. Moreover, the primary aspect of this network is the collaboration between the scientific parts, the regional system, and the industrial system. The involvement of the National Technological Clusters is a proposal of the MIUR in 2012 (Decree No. 257 "Notice for the development and reinforcement of national technological clusters"), as well as national research agencies, such as CNR, INFN, IIT, ENEA, to develop highly qualified scientific research and to support the national development. Considering the policies for the economic development identified by the resolutions of the regional council of the Regione Marche (DGR n.1511/2016, and n. 1035 of 30/7/2018), the present research promotes a more sustainable manufacturing sector. The research focuses on the recovery, re-use, and valorization of industrial by-products from the secondary aluminum industry through their chemical neutralization and synthesis of geopolymer foams. Valorization of the so-called "industrial by-product" is an actual and discussed theme. The industry stakeholders support the achievement of the environmental targets about resource management efficiency, reducing waste output and gas emissions, and constant industrial processes optimization. The development and activation of demanufacturing logistics are essential for improving relative residual values by specific operations and treatments of raw material derived from end-life products and industrial waste. The chemical neutralization of highly reactive materials that come from the treatment processes of scraps (beverage cans and domestic appliances) was investigated through experiments in aqueous alkaline solutions. These metallic aluminum-rich by-products were classified, according to EU law, as dangerous waste, as they can potentially develop flammable gases capable of forming explosive mixtures with air. In this way, they cannot be disposed of in landfills for non-hazardous wastes if chemical neutralization is not planned and performed beforehand. The first experiments were mainly aimed at unraveling the oxidation rate and quantifying the production of hydrogen-rich gases from the reactions of the metallic aluminum-rich by-products in a water-rich alkaline (liquid or vapor) environment. Reactions were carried out in a stainless-steel batch mini-reactor with metering and sampling valves, with the resulting gases analyzed by gas-chromatography (GC). The experimental runs performed in the mini-reactor proved to be effective for eliminating the reactive metallic aluminum, reaching a maximum hydrogen production of 96% of the total gases. All the obtained results can be transferred and applied to (i) the possible industrialization of the method for the chemical neutralization of these dangerous by-products, increasing sustainability and workplace safety, (ii) the use of the resulting hydrogen as a source of energy for the furnaces of the secondary aluminum industry itself, and (iii) new technological materials, e.g., "geopolymer foams (GFs)," by using hydrogen coupled with aluminosilicate materials as a foaming agent. The special hazardous wastes derived from the entire recycling process in the secondary aluminum industry were trapped into these geopolymers. The experimental study affects a vast reality concerning waste management through the recovery, chemical neutralization, and incorporation of these hazardous substances into the GFs. A geopolymeric matrix composed of metakaolin (MK), silica sand (100 wt.% of MK), and chopped carbon fibers (1% wt.% of MK) was doped, adding the industrial by-products from the screening, pyrolysis, de-dusting, and fusion processes with specific contents (1; 2; 3; 4; 5 wt.% of MK). Several experimental tests were carried out to characterize the GFs by the mechanical (flexural, compressive, and Charpy impact strengths) and thermal properties (thermal conductivity, diffusivity, and specific heat).
Geopolymer concrete in recent years has come up as an remarkable solution to reduce the carbon footprints of cement industry thereby reducing its production by completely replacing it with other binders alternatives and making use of polymerization process using alkaline activators such as Sodium silicate, Sodium Hydroxide which activates the alumino-silicate binder and forms a 3D polymeric chain which thereby helps in proper strength development of Geopolymer Concrete. Many cements like products which are mostly fine ashes are being brought into use to analyse their response of replacing it in the mix with cement to analyse their behaviour as to what makes the Geopolymer concrete mix more robust and also the noticing the change in the physiological and chemical aspect. After successful implementation of Fly Ash which is an industry by product, now the agricultural by-products which are fine to satisfactory level are being tested to make concrete strong, and durable. This crucial and necessary development has brought keeping in mind the environment’s daily degradation because of the industries set up a carbon emitting source in their proximity which has to be readily dealt effectively over years. In this paper, we studied developments in Geopolymer concrete, design mixes and used agricultural as well as industrial by products for the use in the Geopolymer concrete and formulate all the research studies done on the production of most conclusive Geopolymer Concrete and make a standard comparison on what seems to be the most economical, durable and consistent mix of Geopolymer concrete, which comprises of various types of binders including Fly Ash, a byproduct of coal obtained from thermal power plant; Sugarcane Bagasse Ash, a byproduct of sugar mill industry; Rice husk ash, which is the ash obtained of the byproduct of rice mill industry.
Full-text available
How to cite this paper: J. Davidovits and F. Davidovits, Geopolymer and Archaeology (2020) 36-43. DOI: 10.13140/RG.2.2.10021.93929/1. The studies carried out in 2017-2018 on the monumental stones constituting the Pumapunku site in Bolivia (South America) provided evidence that the stones are ancient artificial geopolymers (Parts I to III). To make geopolymer andesite stone, around AD 600 to AD 700, the builders could have transported an andesite stony material having the consistence of sand from the Cerro Khapia volcano site, and added an organo-mineral geopolymer binder manufactured with local biomass ingredients. They did not use the many quadrangular volcanic blocks, the famous "piedras cansadas”, the tired stones, which are still lying on both sides of the lake Titicaca. The present paper describes how the builders of Pumapunku / Tiwanaku exploited a natural volcanic andesite sand from the volcano Cerro Khapia, transported and stored it at the shore village of Iwawe, Stratum (V) in the excavation by Isbell & Burkholder, (2002). For the making of their andesite geopolymer monuments, they did not need to crush andesite rock. This andesite sand is similar to one of the pozzolana sands found in the best ancient Roman mortars and coined in Latin “carbunculus”, 2000 years ago.
A new type of red mud/slag/wastewater-based geopolymeric grouts (RSW) was prepared to solve the problem of wastewater and red mud to environment and promoting the safe construction of geotechnical engineering. The applicability of RSW was investigated using different red mud, alkali activator and wastewater dosage. Fourier transform infrared spectrum (FTIR), X-ray diffraction (XRD), semi-calorimetry, Scanning electron microscope−energy dispersive spectrometer (SEM−EDS), and ²⁹Si Magic Angle Spinning (MAS) Nuclear Magnetic Resonance (NMR) were conducted to study the effect of wastewater on RSW. The results showed that wastewater has an accelerating effect on the geopolymerization process of RSW, the mechanical strength increased first and then decreased with the increment of wastewater dosage, the 28 d compressive strength of RSW was 30.2 MPa, which is higher than the cement-based grouts. The leaching of heavy metals were lower than 0.4 mg/L, which demonstrates that the RSW has a good immobilization effect on the heavy metals. The FTIR and SEM−EDS analysis results showed that the ions in wastewater could participated in the geopolymerization process and the hydrated products has a immobilization effect on the heavy metals. Overall, this contribution explores utilizing red mud and wastewater, and preparing high performance grouts for underground engineering.
Full-text available
The additive manufacturing technologies are fast-developing industrial sector and, potentially, a ground-breaking technology. They have many advantages such as the saving of resources and energy efficiency. However, the full exploitation of 3D printing technology for ceramic materials is currently limited; a lot of research is being conducted in this area. A promising solution seems to be geopolymers, but its application requires a better understanding of the behaviour this group of materials. This article analyses the influence of microstructure on mechanical properties whilst taking the production method into consideration. The paper is based on comparative analysis – the investigation is focused on the influence of material structure on the mechanical properties and fracture mechanism of these kinds of composites, including those reinforced with different kind of fibres. As a raw material for the matrix, fly ash from the Skawina coal power plant (located in: Skawina, Lesser Poland, Poland) was used. The investigation was made by SEM analysis. The results show that the microstructural analysis did not sufficiently explain the underlying reasons for the observed differences in the mechanical properties of the composites.
Full-text available
Geopolymers are ceramic-like inorganic polymers produced at low temperature, generally below 100 °C. They consist of chains or networks of mineral molecules linked with covalent bonds. The raw materials are mainly minerals of geological origin, hence the name "geopolymer". They comprise several molecular units for example: silico-oxide (Na, K)-(-Si-O-Si-O-) for (Na, K)-poly(silicate) or (Na, K)-poly(siloxonate), silico-aluminate (Na, K)-(-Si-O-Al-O) for (Na, K)-poly(sialate), ferro-silico-aluminate (Na, K)-(-Fe-O-Si-O-Al-O-) or (Na, K)-poly(ferro-sialate), alumino-phosphate (-Al-O-P-O-) for poly(alumino-phosphate), formed in a geopolymerization process. We focus here on the reactivity of calcined kaolinite, an aluminosilicate oxide Si2O5Al2O2, metakaolin, which led to the discovery of geopolymers 40 years ago. A distinction is made between two synthesis routes: alkaline medium (Na+, K+, Li+, Ca++, Cs+ and the like) and acidic milieu (phosphoric acid, organic carboxylic acids). The alkaline route is the most important, so far. NMR spectroscopy provides data on the molecular structure and polymeric character. The geopolymerization mechanism starts with polycondensation of oligomers into small ribbon-like molecules. This intermediary stage involves several Si-OH groups together with H2O molecules. It is referred to as NASH or KASH by some cement scientists and generalized to the final geopolymer structure. The poly(sialate) final structure consists of well-polymerized individual elementary nanoparticles of 5 to 40 nmin size.
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It is the aim of this contribution to test whether organic-inorganic interactions could induce the formation of authigenic albite. This concept and related results are being compared with modelling scenarios which are purely based on inorganic geochemical reactions. In order to unravel the pathway of authigenic albite formation, this paper presents results of a multidisciplinary study from imaging, geochemistry, mineralogy, and hydrogeochemical modelling. The Jurassic reservoir sandstones of the Magnus oilfield (UK, North Sea) were chosen as a test site. Albite occurs with 4-18 wt.% in the Magnus sandstones and its contents vary with depth. However, albite contents increase with increasing K-feldspar contents and decreasing grain size. It occurs in three forms: (1) as lamellae in perthite, (2) as overgrowth on/in corroded feldspar, and, (3) as cloudy replacing albite patches in K-feldspar. The albite overgrowth has the highest chemical purity (100% albite) whilst albite lamellae and replacing albite patches are slightly less pure (containing 1-4% anorthite). Albite appears non-altered, and has a euhedral morphology and dull cathodoluminescence. It commonly co-occurs with corroded K-feldspar grains. The precipitation of diagenetic albite in the Magnus sandstones is attributed to deep burial 80Ma ago and may have continued until today at temperatures between 90-120°C. The results of hydrogeochemical modelling offer two possible pathways for the authigenic albite formation: (1) Dissolution of unstable minerals (such as kaolinite and chalcedony) coupled to reduction of ferric iron minerals by products generated during oil generation, migration and degradation; (2) Dissolution of non-end member feldspar, such as K-feldspar with 10% albite, coupled to illite formation can account for trace amounts of albite due to an elevated Na+/K+ activity ratio in the pore water.
Conference Paper
Full-text available
The hypothesis that the limestone that constitutes the major pyramids of the Old Kingdom of Egypt is man-made stone, is discussed. Samples from six different sites at the traditionally associ- ated quarries of Turah and Mokattam have been studied using thin-section, chemical X-Ray analy- sis and X-Ray diffraction. The results were compared with pyramid casing stones of Cheops, Teti and Seneferu. The quarry samples are pure limestone consisting of 96-99% Calcite, 0.5-2.5% Quartz, and very small amount of dolomite, gypsum and iron-alumino-silicate. On the other hand the Cheops and Teti casing stones are limestone consisting of: calcite 85-90% and a high amount of special minerals such as Opal CT, hydroxy-apatite, a silico-aluminate, which are not found in the quarries. The pyramid casing stones are light in density and contain numerous trapped air bubbles, unlike the quarry samples which are uniformly dense. If the casing stones were natural limestone, quarries different from those traditionally associated with the pyramid sites must be found, but where? X- Ray diffraction of a red casing stone coating is the first proof to demonstrate the fact that a compli- cated man-made geopolymeric system was produced in Egypt 4,700 years ago.
A comparison was made of the solid-state 29Si, 27Al and 43Ca MAS NMR spectra of the outer casing stone from Snefru's Bent Pyramid in Dahshour, Egypt, with two quarry limestones from the area. The NMR results suggest that the casing stones consist of limestone grains from the Tura quarry, cemented with an amorphous calcium-silicate gel formed by human intervention, by the addition of extra silica, possibly diatomaceous earth, from the Fayium area.
Geology of the Western and Altiplano Mountains west of Lake Titicaca in southern Peru
  • O Palacios
O. Palacios, Geology of the Western and Altiplano Mountains west of Lake Titicaca in southern Peru. Bulletin A42 (1993) 80.