STOP promoting fly ash-based cements !

by Prof. Dr. Joseph Davidovits, 

Geopolymer Institute, Saint-Quentin (France)

A continent is on fire. Both Australia and California have never experienced such an inferno. More and more citizens are blaming the climate change (that is CO₂ emissions) responsible for this. But the governments of Australia, along with the U.S., Russia, Brazil, China, India, Poland, South Africa and also Germany – where coal mining and coal-power plants are significant industries and with powerful lobbies – are entrenched and want to stick to their coal policy and business.

Fly ash-based cement is supporting the burning of coal:

The demand for coal in electricity power plants is steadily increasing in the world and consequently generates more and more fly ash. Power plants are lobbying the cement and building industry with so-called low-CO₂ fly ash-based cements. The fact that fly ash is used to make building materials is an excuse to increase coal production. Therefore, any development and implementation of fly ash-based cement is supporting the burning of coal in the production of electricity and increasing CO₂ emission.

But, do you know that the manufacture of 1 metric tonne of fly ash is generating 33 metric tonnes of CO₂ emission? This fact has been overlooked by all experts, including United Nations Environment experts and myself. Indeed, the burning of 10 t Carbon (C=12 g/mol.) produces 36.66 t of CO₂ (CO₂ = 44 g/mol.). But the burning of coal generates 10% by weight of fly ash. In other words, 10 t coal are producing 1 t fly ash and emit 33 t CO₂.

All taken-for-granted ideas and promotional slogans about low-CO2 cements based on fly ash are totally wrong:

Consequently, 1 t of fly ash-based geopolymer cement containing 50% by weight of fly ash, should be associated with 16.5 t of CO₂ emission. Accordingly, 1 t of blended-OPC containing 50% by weight of fly ash, should also be linked to an additional 16.5 t of CO₂ emission. These numbers seem extravagant but they do represent scientific reality, particularly if we compare them with those numbers published in the past for geopolymer cement: 0.2 t CO₂/1 t GP-cement, as well as for Portland cement: 0.9 t CO₂/1 tonne OPC. All taken-for-granted ideas and promotional slogans about low-CO₂ cements based on fly ash are totally wrong.

Experts are stating that this CO₂ does not count because it has already been spent in the production of electricity. But we understand that this production has no future because it is harmful to the global climate. Therefore, the production of fly ash-based cement is not a long-term solution. Admittedly, the material is available and sometimes stored in large quantities. But I think it is not suitable for mass production, only for local niche markets or technical specialties.

Therefore, we should stop promoting coal-fly ash-based geopolymer cements. The solution is to develop and implement geopolymeric systems relying solely on geological resources, such as Ferro-sialate geopolymer cement and the like.

The geological raw material is available worldwide and long-term stability has been demonstrated. There is no reason why scientists around the world should not be working on it. See our recent article on Ferro-sialate Geopolymers in the Geopolymer Institute Library at Technical Paper Nr27 Ferro-sialate. A special session will be dedicated to this topic at the next Geopolymer Camp 2020, July 6-8.

Joseph Davidovits, 12/01/2020.

False Values on CO₂ Emission for Geopolymer Cement/Concrete Published in Scientific Papers

Adapted from the article originally published in Elsevier’s internet site “Materials Today” at Environmental Implications of Geopolymers, 29 June 2015. See also the presentation at the Geopolymer Camp 2015. See also the news Virtual Journal on Geopolymer Science .

LCA of commercialised geopolymer cement/concretes are seldom. This is due to proprietary reasons. Presently they are based on Type 2 slag/fly ash/alkali-silicate system (see Technical papers #21, #22, #23 in the Library). Geopolymer Type 2 concrete and standard Portland concrete are similar in non- binder materials used and behaviour after production; there is some dilution of the benefits when measured over the full life cycle (LCA). The greenhouse gas emissions during the life cycle of Geopolymer Type 2 concrete are approximately 62%-66% lower than emissions from the reference concrete. The Type 2 geopolymer cement has ca. 80% lower embodied greenhouse gas intensity than an equivalent amount of ordinary Portland cement binder used in reference concrete of a similar strength, confirming the data published by the Geopolymer Institute, where the reductions are in the range of 70 % to 90 % (see Technical paper #21). These values do not include any additional external constraints like transport from or to the utility. They reflect the actual potential as soon as industrialization starts in full swing.

On the opposite, several published scientific LCA papers claim that, in terms of CO₂ emission, geopolymer cement was not better than Portland cement, and worse for other parameters. These statements are based on methodological errors and false calculations of the CO₂ emission values for geopolymer cement/concrete. The problem is that these false values are taken for granted by other scientists without any further consideration.

The present paper “False Values on CO₂ Emission for Geopolymer Cement/Concrete Published in Scientific Papers” cites and explains the methodological errors and false calculations.

Click here to see how to download paper nr 24 False-CO2-values.pdf.

Queensland’s University GCI building with 3 suspended floors made from structural geopolymer concrete. Credit: Hassel Architect

The 4 story high building, for general public use, comprises 3 suspended geopolymer concrete floors involving 33 precast panels. They are made from slag/fly ash-based geopolymer concrete coined Earth Friendly Concrete (EFC), a Wagners brand name for their commercial form of geopolymer concrete.

Detailed information to be found at
Hassel Architect
Wagners Australia
Architecture Univ. Queensland

Prof. Joseph DAVIDOVITS

CONTENT

1. Introduction
2. Portland cement chemistry vs Geopolymer cement chemistry
   2.1 Alkali-activated materials vs Geopolymer cements.
   2.2 User-friendly alkaline-reagents
3. Geopolymer cement categories
   3.1 Slag-based geopolymer cement
   3.2 Rock-based geopolymer cement
   3.3 Fly ash-based geopolymer cements
   3.4 Ferro-sialate-based geopolymer cement
4. CO2 emissions during manufacture
   4.1 CO2 emission during manufacture of Portland cement clinker
   4.2 Geopolymer Cements Energy Needs and CO2 emissions
      4.2.1 Rock-based Geopolymer cement manufacture involves:
          4.2.1.1 Energy needs
          4.2.1.2 CO2 emissions during manufacture
      4.2.2 Fly ash-based cements Class F fly ashes
5. Properties for Rock-based geopolymer cement (Ca,K)-poly(sialate-disiloxo)
6. The need for standards
References

Click here to see how to download paper nr 21.

The last few years have seen spectacular technological progress in the development of geosynthesis and geopolymeric applications.

New state-of-the-art materials designed with the help of geopolymerisation reactions are opening up new applications and procedures, and transforming ideas that have been taken for granted in inorganic and mineral chemistry.

Since the discovery of the geopolymer chemistry by Prof. Joseph Davidovits (see also in the Library the scientific paper IUPAC 1976) this new generation of materials, whether used pure, with fillers or reinforced, is already finding applications in all fields of industry. These applications are to be found in the automotive and aerospace industries, non-ferrous foundries and metallurgy, civil engineering, cements and concretes, ceramics and plastics industries, waste management, art and decoration, retrofit of buildings, etc. One third of the recently updated book Geopolymer Chemistry & Applications is dedicated to geopolymeric applications. You may also go to the Geopolymer Library and download several papers, for example #21 Geopolymer cement review 2013.

Some of the geopolymer applications are still in development whereas others are already industrialized and commercialized. They will be listed in six (6) categories, namely:

Geopolymer Precursor

Geopolymer Resin, paint, binder, grout

Geopolymer cement, concrete, waste management, global warming

Applications with geopolymer cements and concretes are described in the section Geopolymer Cement with special emphasis on the introduction of user-friendly systems. It is striking to notice that Geopolymer cements manufacture emits 80 to 90% less CO₂ (greenhouse effect gas) than Portland Cement. See in GLOBAL WARMING. They are perfect examples of Green Chemistry and Sustainable Development.

For information on Fly Ash-based geopolymer cements go to European Research Project GEOASH. For updated very recent detailed information, read Chapters 12, 24, 25 in Geopolymer Chemistry & Applications; you may also download previous papers in the Library .

Rock-based geopolymer cements are ideal for environmental applications, such as the permanent encapsulation of radioactive and other hazardous wastes, toxic metals, as well as sealants, capping, barriers, and other structures necessary for remedying toxic waste containment sites (see our European Research Project GEOCISTEM and the GEOPOLYTECH process). See also in the Library .

Rock-based geopolymer cements and concretes for building and repairing infrastructure have very high early strength, their setting times can be entirely controlled, and they remain intact for a very long time without the need for repair. See in Davidovits’ book, Geopolymer Chemistry & Applications, the Chapters 9, 10, 24 and 25. The strength of geopolymeric rock-based geopolymer concrete is such that a heavy Boeing or Airbus can land on a runway freshly patched with geopolymeric rock-based geopolymer concrete only four hours after patching has been completed. The discovery of this new cement was awarded with a Gold Ribbon by the American National Association for Science, Technology and Society (NASTS) in 1994 (Library paper #3 NASTS award ).

Geopolymer specialty

Geopolymer ceramic

Several decades ago, ceramicists tried to manufacture ceramic tiles at temperatures lower than 450°C, without firing. Geopolymer science masters the transformation of kaolinite, the major component of ceramic clays, into geopolymers of the poly(sialate) and poly(sialate-siloxo) types. Application of this chemistry yielded several technological breakthroughs pertaining to LTGS, Low-Temperature-Geopolymeric-Setting and geopolymerized modern ceramic processing. See in Chapter 23 of Davidovits’ book Geopolymer Chemistry & Applications .

Geopolymer high-tech/ fiber reinforced composite

Geopolymer composites have three main properties that make them superior to ceramic-matrix composites, plastics, and organic composite materials.

First:
Geopolymers are very easy to make, as they handle easily and do not require high heat.
Second:
Geopolymeric composites have a higher heat tolerance than organic composites. Tests conducted on Geopolymer carbon-composites showed that they will not burn at all, no matter how many times ignition might be attempted.
Third:
The mechanical properties of Geopolymer composites are as good as those of organic composites. In addition, Geopolymers resist all organic solvents (and are only affected by strong hydrochloric acid).

Before the discovery of geopolymerization, these three critical properties had not been incorporated into any one material. More information are available in applications called GEO-COMPOSITE and GEO-STRUCTURE and in Davidovits’ book Geopolymer Chemistry & Applications , Chapter 21.

An Example of the Development of Geopolymeric Composites and Cements That Improves Air Travel Safety and Airport Efficiency*

The Chapters of the book GEOPOLYMER Chemistry & Applications dedicated to these applications are referred to in italic.

A jet is preparing for takeoff from a runway in New York as a crew begins placing a section of geopolymer concrete (Chapters 24, 25) on a Los Angeles runway. The plane is equipped with a fire-resistant geopolymer-encased electronic flight recorder. The jet’s cabin has also been rendered fireproof with sandwich panels of carbon/Geopolymite® composites (Chapter 21) and geopolymer foam insulating boards (Chapter 22). The jet is also equipped with a highly advanced fireproof air filter. Several structural components of the jet, made with an advanced SPF Al superplastic aluminum alloy, have been manufactured at 550°C using compression ceramic tools made of geopolymer materials (Chapter 20).

When the plane is ready to land in Los Angeles, the runway repaired with Pyrament® concrete will be ready for it.

*This fictitious example illustrates possible applications that are or have been manufactured and/or patented by several companies

• Khon Kaen University, Sustainable Infrastructure Research and Development Center, (SIRDC),
• Thai Geopolymer Network
• Thai Concrete Association

and will be held on 24-25 May, 2006 at Sofitel Raja Hotel, Khon Kaen, Thailand.

The program on Geopolymer includes :

• Development of geopolymer
• Use of different stock feeds such as fly ash, claimed clay, rice husk ash
• Bridging the concrete gaps-advantages of geopolymer
• Early commercial products
• Sustainability, etc.

Download the program at the Internet site

Up to 90% reduction of CO₂ Greenhouse Gas emission during cement manufacture

Professor J. Davidovits started working on CO₂ emissions mitigation as earlier as 1990, at PennState Materials Research Laboratory, Pennstate University, USA. Unfortunately, American Agencies (DOE and EPA) stated that this was not an important issue and both institutions declined to support research proposals.
In this section we develop:
a) Rock-based Geopolymer cements;
b) Fly ash-based Geopolymer cements

Ordinary cement, often called by its formal name of Portland cement, is a serious atmospheric pollutant. Studies have shown that one ton of carbon dioxide gas is released into the atmosphere for every ton of Portland cement which is made anywhere in the world. The only exceptions are so-called ‘blended cements’, using such ingredients as coal fly ash, where the CO₂ emissions are slightly suppressed, by a maximum of 10%-15%. There is no known technology to reduce carbon dioxide emissions of Portland cement any further.

European cement manufacturers are confronted with the EC CO₂ eco-tax proposal and are lobbying Brussel’s Administration. They claim that the eco-tax would have a negative effect on the competitiveness of the European cement industry. The planned CO₂ eco-tax on energy is likely to induce industries to move abroad. The representative of one of the world leading cement experts argues that ”(…) if Europe is the only one to adopt it [the eco-tax], it will be more profitable to install our factories in Algiers [North Africa], rather than in Marseille [France]. Freight costs would be equivalent to the increase in manufacturing costs (…)”. This statement does not reflect the true scope of the issue, which was addressed by J. Davidovits at the 5th GLOBAL WARMING International Conference (see «Global Warming Impact On the Cement and Aggregates Industries», in World Resource Review Vol. 6, N°2, 263-278, 1994) (see in LIBRARY the paper #5 Global Warming ). The burden would be shifted towards third world countries and international cement production would continue to grow.

Cement, (Portland cement), results from the calcination of limestone (calcium carbonate) at very high temperatures of approximately 1450-1500°C, and silico-aluminous material according to the reaction

5CaCO₃ + 2SiO₂ —> (3CaO,SiO₂) + (2CaO,SiO₂) + 5CO₂

this means that the manufacture of 1 metric tonne of cement generates 1 metric tonne of CO₂ greenhouse gas.

As time passes by, Portland cement manufacture increases CO₂ emissions, and, therefore, the predicted BaU (Business as Usual) values for future atmospheric CO₂ concentration should be corrected accordingly.

Assuming a 5% yearly increase, in year 2015 world cement CO₂ emissions could equal the 3,500 millions tonnes presently emitted by European (E.U.) industrial activities (industry + energy + transportation), or 65% of the present total U.S. CO₂ emissions . This illustrates the need for new technologies to be adapted to the economy of developing countries.

Estimated World Cement CO₂, Million Metric Tonnes (MT),
in year 1988, 2000 and 2015, after J. Davidovits (1990).
In 2015 World Cement CO₂ = total Europe or 67% of total USA

Unless something drastic and different is done, the world’s atmosphere will go on being destroyed by the production of Portland cement, which is a far worse source of atmospheric pollution than the oil industry or any other known industry. The fact that the dangers to the world’s ecological system from the manufacture of Portland cement is so little known by politicians and public makes the problem all the more urgent: when nothing is known, nothing is done.
This situation clearly cannot continue if the world is going to survive. The conversion of existing cement factories to clean production of geopolymeric cement does not necessitate any re-equipment. The same grinders and the same ovens can be retained for the new process, but the ovens are merely run at half-temperature. For geopolymeric cement production, no temperature higher than 750°C is ever needed. This means that only one third of the fuel requirement is needed for cement production, and of course the fuel emissions are thus reduced by two thirds. This means local benefits for coal-burning regions, with drastic reductions in sulfur dioxide and nitrogen emissions, as well as suppression of particulate emissions. But the main benefits of geopolymeric cements are the reductions in carbon dioxide: the chemical process emits zero carbon dioxide, and the fuel much less, so the end result is a reduction in carbon dioxide emissions for cement manufacture of between 80% and 90%.

There is no other existing and proven technology in the world today which offers such hope for saving the world’s atmosphere.

In the recently updated book Geopolymer Chemistry & Applications Low-CO₂ geopolymer cement applications are thoroughly outlined in Chapters 9, 10, 11, 12 and 24.

From the scientific press: NEW SCIENTIST, 19 July 1997, page 14

THE CONCRETE JUNGLE OVERHEATS:
Estimates of carbon dioxide emissions from one of the world’s growth industries
have been grossly underestimated.
“CEMENT kilns contribute more to the world’s output of carbon dioxide than aircraft and could soon be responsible for 10 % of all emissions of the greenhouse gas. New calculations by an industry scientist reveal that cement manufacturers already produce 7 % of global CO₂ emissions-almost three times previously published estimates, and that CO₂ output is increasing faster from cement works than from any other industrial source.
Cement production creates CO₂ in two ways: by the conversion of calcium carbonate to calcium oxide inside the kilns, and by burning large quantities of fossil fuels to heat the kilns to the 1450°C necessary for roasting limestone. Previous estimates for CO₂ emissions from cement production have concentrated only on the former source. The UN’s Intergovernmental Panel on Climate Change puts the industry’s total contribution to CO₂ emissions at 2.4 %; the Carbon Dioxide Information Analysis Center at the Oak Ridge National Laboratory in Tennessee quotes 2.6 %.
Now Joseph Davidovits of the Geopolymer Institute, a research institution based in Saint-Quentin, Picardie, France, has for the first time looked at both sources. He as calculated that world cement production of 1.4 billion tonnes a year produces 7 % of current CO₂ emissions. This puts it behind power generation and vehicle exhausts as a source of the gas, but ahead of aircraft, which have excited huge attention from politicians concerned about curbing global warming.
Dale Kaiser at Oak Ridge confirmed this week that “our calculation only singles out the chemical transformation aspect”. (…) John Lanchbery director of environmental projects at the Verification Technology Information Centre in London, who analyses national CO₂ emissions inventories, says: “Cement is well known as the biggest manufacturing source of CO₂, but I certainly had no idea the total was as high as is being suggested.”
Globally cement production is rising by 5 % a year, says Davidovits. He predicts that it will be responsible for a tenth of global CO₂ emissions by 2000. It is growing fastest in the “tiger” economies of east Asia, where construction of buildings, roads and other infrastructure is booming. In Korea, the industry is already responsible for an estimated 13 % of the country’s CO₂ emissions. (…) The silence on cement manufacture as a cause of global warming contrasts with the growing concern over aircraft emissions, which are estimated to contribute a maximum of 5 %. Last month at the Earth Summit in New York, the European Union called for a global tax on aircraft fuel. But proposals for an internal EU tax on energy aimed at reducing CO₂ emissions, specifically excluded the cement industry because its energy use is so high that it was thought a tax would damage it. Fred Pearce

Rock-based Geopolymer cements reduce CO₂ emission by 80 %

The technology developed for Rock-based Geopolymer cements reduces CO₂ emission by 80%. Geopolymeric cements are manufactured in a different manner than Portland cement. Geopolymers do not rely on the calcination of calcium carbonate and therefore do not release bounded CO₂. They also do not require extreme high temperature kilns, with large expenditure of fuel, nor do geopolymers require such a large capital investment in plants and equipment. The mechanical properties of these novel geopolymeric cements are similar to those of regular Portland cement. Appropriate geological resources are available on all continents for providing suitable raw materials. The issue of long term durability was studied in relation with archaeological analogues, namely ancient Roman cements. A new linguistic study of the Latin author Vitruvius’ famous book «De Architectura» (1st century B.C.) outlines the unique properties of a “carbunculus” cement, which was manufactured by calcining geological materials (see in Archaeo-Analogues and in the paper #E Searching for Carbunculus ). During cement manufacture, this re-created ancient Roman cement reduces CO₂ emissions by 55-60%.

Introducing low-CO₂ Rock-based Geopolymer cements would, on one hand, allow unlimited development of concrete infrastructures for the Global Economy and, on the other hand, dramatically mitigate CO₂ Greenhouse Gas emissions. The European industrial research consortium GEOCISTEM (European multidisciplinary Brite Euram industrial research project funded by the European Commission) developed Rock-based Geopolymer cements that mitigate CO₂ emissions by 80%. See the results on the page GEOCISTEM.

Successful accomplishment of the GEOCISTEM exemplifies the theoretical studies of the Background knowledge (see the Research Project Global Warming and in the LIBRARY the paper #5 Global Warming, and also for example #21 Geopolymer cement review 2013) and demonstrates that it is possible to manufacture new cements with low-CO₂ emission during their fabrication, to minimize the «Green House» Global-Warming. The Table and Figure show interesting data on energy cost and CO₂ emission for Portland cement and for three types of geopolymeric cements developed during the GEOCISTEM project: glass cement and two CARBUNCULUS cements

Cement type	Manufacturing temperature	Energy consumption	CO2 emission
Portland	1450-1500°C	100	100
Glass	750°C-1350°C	64 (-36%)	35 (-65%)
Carbunculus	750-800°C	40 (-60%)	20 (-80%)
Carbunculus	nat. 20-80°C	30 (-70%)	10 (-90%)

Comparison between Energy consumption and CO₂ emission
during manufacture, for various cement types, assuming Portland=100

Fly ash-based cements: the GEOASH project

Fly ash-based geopolymer cements reduce CO₂ emissions by 90% when compared to Portland cement. The GEOASH (2004–2007) project was carried out with a financial grant from the Research Fund for Coal and Steel of the European Community. The GEOASH project is known under the contract number RFC-CR-04005. It involves: Antennuci D., ISSeP, Liège, Belgium; Nugteren H.and Butselaar-Orthlieb V., Delft University of Technology, Delft, The Netherlands; Davidovits J., Cordi-Géopolymère Sarl, Saint-Quentin, France; Fernández-Pereira C. and Luna Y., University of Seville, School of Industrial Engineering, Sevilla, Spain; Izquierdo M. and Querol X., CSIC, Institute of Earth Sciences “Jaume Almera”, Barcelona, Spain.

Seventeen samples of (co-)combustion European fly ashes were tested on their suitability for geopolymeric cements. Normally, curing of fly ash-based matrices is done at temperatures between 60 and 90°C. In this project, since the idea is to use the geopolymer as a cement, the curing is taking place at ambient temperature, with a modified (Ca,K)-based geopolymeric system. The Final Technical and Scientific Report was presented mid 2008. Detailed information may be found in the Technical paper #22 at GEOASH: fly ash-based geopolymer cements as well as in the updated 3rd edition of Davidovits’ book Geopolymer Chemistry & Applications, Chapter 12.

Two methods were used and compared with. One, called the classical or conventional method, relies on alkali-activation and pure NaOH (8M, 12M), i.e. User-hostile conditions. The second is based on geopolymerization with (Ca,K,Na) geopolymeric systems, i.e. User-friendly conditions. A recent video stresses the major differences between alkali-activation and geopolymerization in Why Alkali-Activated Materials are NOT Geopolymers ?. The geopolymeric method was developed for the implementation of all kind of geological materials, eg. Rock-based geopolymers. The (K,Na,Ca)-poly(sialate-siloxo) process is based on the system fly ash / slag / Ksil / H₂O reacting at room temperature. The ashes, 60-80% by weight of the mix, were mixed with the geopolymeric slurry containing alkali-silicate solution (molar SiO₂:M₂O > 1.40), blast furnace slag and water, and cured at room temperature.

The investigations by Palomo and his team (Fernández-Jiménez and Palomo, 2003), are often taken in the literature as a reference. They claim that the pure NaOH based zeolitic system should be considered as the reference in the determination of the chemical parameters leading to a material with optimal binding properties. According to these standard criteria, any fly ash with a mullite content higher than 5% is not suitable and may not be used. Six fly ashes were selected and submitted to this criteria. The results are shown in the Figure below. Only two fly ashes, CSIC-4 and CSIC-5 have mullite content lower than 5% and might work with alkali-activation. The Figure displays the results of the (Ca,K)-based geopolymeric method. It shows the 28 day compressive strength obtained in relation with the mullite content. All values are higher than 50 MPa, the majority reaching strengths higher than 70 MPa. It is therefore important to notice that practically all class F fly ash types, i.e. those with low free CaO, can be used with this user-friendly system.

It has also been measured that for a given fly ash, the conventional alkali-activation (zeolitic method) provides lower compressive strength than the (Ca,K,Na)-based geopolymeric procedure. The geopolymeric method yields higher strengths as well as lower costs (no thermal activation needed) and safer and easier handling treatment, i.e. user-friendly.

Compressive strength at 28 days in relation with mullite content, room temperature curing (GEOASH).

From 2001, we have conducted some important research on the development, manufacture, behaviour, and applications of Low-Calcium Fly Ash-Based Geopolymer Concrete. This concrete uses no Portland cement; instead, we use the low-calcium fly ash from a local coal burning power station as a source material to make the binder necessary to manufacture concrete. Concrete usage around the globe is second only to water. An important ingredient in the conventional concrete is the Portland cement. The production of one ton of cement emits approximately one ton of carbon dioxide to the atmosphere. Moreover, cement production is not only highly energy-intensive, next to steel and aluminium, but also consumes significant amount of natural resources. In order to meet infrastructure developments, the usage of concrete is on the increase. Do we build additional cement plants to meet this increase in demand for concrete, or find alternative binders to make concrete?

In this work, low-calcium (ASTM Class F) fly ash-based geopolymer is used as the binder, instead of Portland or other hydraulic cement paste, to produce concrete. The fly ash-based geopolymer paste binds the loose coarse aggregates, fine aggregates and other un-reacted materials together to form the geopolymer concrete, with or without the presence of admixtures. The manufacture of geopolymer concrete is carried out using the usual concrete technology methods. As in the case of OPC concrete, the aggregates occupy about 75-80 % by mass, in geopolymer concrete. The silicon and the aluminium in the low-calcium (ASTM Class F) fly ash react with an alkaline liquid that is a combination of sodium silicate and sodium hydroxide solutions to form the geopolymer paste that binds the aggregates and other unreacted materials.

This paper contains 2 reports. The first Report GC1 (curtin-flyash-GP-concrete-report.pdf) describes the mixes and the short term properties. The second Report GC2 (curtin_flyash_GC-2.pdf) provides the long term properties. See the conclusions below.

Click here to see how you can download paper number 17.

Based on the test results, the following conclusions are drawn:
1. There is no substantial gain in the compressive strength of heat-cured fly ash- based geopolymer concrete with age.
2. Fly ash-based geopolymer concrete cured in the laboratory ambient conditions gains compressive strength with age.
3. Heat-cured fly ash-based geopolymer concrete undergoes low creep.
4. The creep coefficient, defined as the ratio of creep strain-to-instantaneous strain, after one year for heat-cured geopolymer concrete with compressive strength of 40, 47 and 57 MPa is around 0.6 to 0.7; for geopolymer concrete with compressive strength of 67 MPa this value is around 0.4 to 0.5.
5. The heat-cured fly ash-based geopolymer concrete undergoes very little drying shrinkage in the order of about 100 micro strains after one year. This value is significantly smaller than the range of values of 500 to 800 micro strain for Portland cement concrete.
6. The drying shrinkage strain of ambient-cured specimens is in the order of 1500 microstrains after three months. This value is many folds larger than that of heat- cured specimens, and the most part of that occurs during the first few weeks.
7. The test results demonstrate that heat-cured fly ash-based geopolymer concrete has an excellent resistance to sulfate attack.
8. Exposure to sulfuric acid solution damages the surface of heat-cured geopolymer concrete test specimens and causes a mass loss of about 3% after one year of exposure. The severity of the damage depends on the acid concentration.
9. The sulfuric acid attack also causes degradation in the compressive strength of heat-cured geopolymer concrete; the extent of degradation depends on the concentration of the acid solution and the period of exposure. However, the sulfuric acid resistance of heat-cured geopolymer concrete is significantly better than that of Portland cement concrete as reported in earlier studies.

Invited Paper, Geopolymer 2002 International Conference, October 28-29, Melbourne, Australia

Environmentally driven geopolymer applications are based on the implementation of (K,Ca)-Poly(sialate-siloxo) / (K,Ca)-Poly(sialate-disiloxo) cements. In industrialized countries (Western countries) emphasis is put on toxic waste (heavy metals) and radioactive waste safe containment. On the opposite, in emerging countries, the applications relate to sustainable development, essentially geopolymeric cements with very low CO₂ emission. Both fields of application are strongly dependent on politically driven decisions.

Click here to see how you can download paper number 16.

CO₂ related energy taxes are focusing essentially on fuel consumption, not on actual CO₂ emission measured at the chimneys. Ordinary Portland cement, used in the aggregates industries, results from the calcination of limestone (calcium carbonate) and silica according to the reaction:

5CaCO₃ + 2SiO₂—> (3CaO,SiO₂ )(2CaO,SiO₂ ) + 5CO₂

The production of 1 tonne of cement directly generates 0.55 tonnes of chemical-CO₂ and requires the combustion of carbon-fuel to yield an additional 0.40 tonnes of CO 2 . To simplify: 1 T of cement = 1 T of CO₂. The 1987 1 billion metric tonnes world production of cement accounted for 1 billion metric tonnes of CO₂ , i.e. 5% of the 1987 world CO₂ emission. A world-wide freeze of CO₂ emission at the 1990 level as recommended by international institutions, is incompatible with the extremely high cement development needs of less industrialized countries. Present cement production growth ranges from 5% (China, Japan) to 16% (Korea, Thailand) and suggests that in 25 years from now, world cement CO₂ emissions could equal 3,500 million tonnes. Eco-taxes when applied would have a spectacular impact on traditional Portland cement based aggregates industries. Taxation based only on fuel consumption would lead to a cement price increase of 20%, whereas taxation based on actual CO₂emission would multiply cement price by 1.5 to 2. A 25-30% minor reduction of CO₂ emissions may be achieved through the blending of Portland cement with replacement materials such as coal-fly ash and iron blast furnace slag.

In year 2015, assuming that world Global Climate treaties might authorize an amount of this Portland blended cement production in the order of 1850 million tonnes, the complementary need for new low-CO₂ cementitious materials, in the range of 1650 million tonnes, requires the introduction of a different technology. Novel geopolymeric poly(sialate-siloxo) cements, which do not rely on the calcination of limestone (and accompanying release of CO₂ ), are low-CO₂ cementitious materials providing similar properties than current high-CO₂ Portland cement. The technology reduces CO₂ emission caused by the cement and aggregates industries by 80%. Global Warming Impact on the Cement and Aggregates Industry.

Click here to see how you can download paper number 5.

In the aftermath of various catastrophic fires in France between 1970-73, which involved common organic plastic, research on non-flammable and non-combustible plastic materials became my objective. I founded a private research company in 1972, which is today called CORDI-GÉOPOLYMÈRE. In my pursuit to develop new inorganic polymer materials, I was struck by the fact that simple hydrothermal conditions govern the synthesis of some organic plastics and also heat-resistant mineral feldspathoids and zeolites. The scientific and patent literature indicate that, before 1978, the geochemistry that yields the synthesis of zeolites and molecular sieves had not been investigated for producing mineral binders and mineral polymers. I proceeded to develop amorphous to semi-crystalline three-dimension alsilico-aluminate materials, which I call «geopolymers» (mineral polymers resulting from geochemistry). These reactions are of the poly(sialate), poly(sialate-siloxo/ disiloxo) types. Geopolymerization involves a chemical reaction between various alumino-silicate oxides Al3+ in IV-V fold coordination) with silicates, yielding polymeric Si-O-Al-O sialate bonds like the following:

2(Si₂O₅,Al₂O₂)+K₂(H₃SiO₄)₂+Ca(H₃SiO₄)₂—> (K₂O,CaO)(8SiO₂,2Al₂O₃,nH₂O)

Geopolymers involved in materials developed for industrial applications, are non-crystalline. Nuclear Magnetic Resonance 27Al and 29Si(MAS-NMR) spectroscopy provide some insight into their molecular frameworks.Other than my archaeological research on ancient cements, my research has been purely industrial. Thus, almost all of the scientific literature concerning geopolymerization is found in the patent literature.

The Industrialization of Geopolymeric Products

Our subsidiary company, GEOPOLYMERE sarl (France), was founded in 1984 in association with my brothers Michel Davidovics and Nicolas Davidovits. Our products include advanced mineral binders that withstand harsh environmental conditions, high temperature stable GEOPOLYMITE® binders and GEOPOLYCERAM® compounds, fireproof carbon/geopolymer composites. Some US Patents are: J. Davidovits US 3,950,470 (1976); 4,349,386 (1982); 4, 472,199 (1984); 4,859,367 (1989); 5,288,321(1994); J. Davidovits and J.J. Legrand US 4,028,045 (1977); N.Davidovits, M. Davidovics and J. Davidovits US 4,888,311 (1989); other patents granted in 1994 or pending. In the USA, LONE STAR INDUSTRIES Inc. began product development in 1983, and in 1988 this company introduced PYRAMENT®, a new class of special blended cements; US Patents: J. Davidovits and J.L. Sawyer US 4,509,985 (1985); R.F. Heitzmann, M. Fitzgerald and J.L. Sawyer US 4,642,137 (1987); R.F. Heitzmann, B.B. Gravitt and J.L. Sawyer US 4,842,649 (1989). In Germany, HÜLS TROISDORF AG began product development in 1982 (Dynamit-NobelAG).

Newly industrialized Geopolymeric Products

In Europe, the multidisciplinary BriteEuram industrial research project GEOCISTEM (see time chart), is preparing to introduce acid-resistant Poly(sialate-siloxo) cements for restoring sites highly contaminated with uranium mining waste (WISMUT sites in former East-Germany). This project also provides new geopolymeric cements that can help address the problem of global warming by reducing 80% of the CO₂ emissions produced by the cement industries.

Click here to see how you can download paper number 3.

Other interesting publications on the same topic of aluminosilicate polymers

We recommand following recent papers published in 1996-1997 by a research group at Free University of Brussels (V.U.B.), Belgium. These papers confirm the presence of a polymeric structure for aluminosilicates of the geopolymeric type. These papers are excellent for there scientific content but do not deserve any further consideration for there lack of any reference to the scientific papers nor to the numerous issued patents published by Joseph Davidovits and listed in the CHEMICAL ABSTRACTS databank. One of the authors of these papers, Prof. J. WASTIELS, worked with geopolymeric binders supplied by the company Géopolymère (Pont-Ste Maxence, France) and also presented a paper at the First European Conference on Geopolymer, GEOPOLYMER ‘88, 1998, Université de Technologie, Compiègne, France, paper titled: “Composites with Mineral Matrix in Low Energy Construction”, by G. Patfoort and J. Wastiels, in GEOPOLYMER ‘88, J. Davidovits and J. Orlinski Eds.., Volume 2, Paper nr 16, pp. 215-221, 1988. The presentation abstract of this paper, Session D Nr27 (see in GEOPOLYMER ‘88, page 11) reads as follows: “On March 31, 1987, French President Francois Mitterand laid the foundation stone of the new University of Technology at Sevenans, France. This foundation stone was man-made, more precisely had been geopolymerised at 55°C, in our laboratories [at V.U.B.]. Our involvement with geopolymeric reactions goes back to 1982 when we started a collaboration with Prof. J. Davidovits and the Geopolymer Institute. A series of low cost composites for low energy construction are being developed at Vrije Universitet Brussels, starting from aluminosilicates. Geopolymerisation reaction can take place at atmospheric pressure and at low temperatures (between room temperature and 100°C), so that a low amount of energy is used for production. Applications are expected to be found in low cost housing, using locally available raw materials, and more generally in composite materials with geopolymeric matrix”.

• Rahier H., Van Mele B., Biesemans.M., Wastiels J. and Wu X., Low-temperature synthesized aluminosilicate glasses Part I, J. Material Sciences, 31 (1996) 71-79.
• Rahier H., Van Mele B., Wastiels J., Low-temperature synthesized aluminosilicate glasses Part II, J. Material Sciences, 31 (1996) 80-85.
• Rahier H., Simons W., Van Mele B., Biesemans.M., Low-temperature synthesized aluminosilicate glasses Part III, J. Material Sciences, 32 (1997) 2237-2247.

www.wbcsdcement.org/pdf/final_report8.pdf

This report confirms the studies carried out by Prof. Joseph Davidovits since 1990 on CO₂ emissions during Portland Cement manufacture (in the LIBRARY the paper on Global Warming). Batelle’s report recommends the development of geopolymer cement; see on page 25 (39) of the report.

Executive Summary
Climate change has become a prominent global issue, and governments are beginning to take significant steps to address the problem. For the cement industry, the climate change issue carries serious financial consequences, in addition to its environmental importance. Without action, the financial liabilities associated with the industry’s CO₂ emissions will be large. But, through a well-managed strategy, significant financial benefits could accrue to the industry, particularly in the near-term.
Carbon dioxide (CO₂) is the primary greenhouse gas that drives global climate change and is the only greenhouse gas emitted by the cement industry in a significant amount. The cement industry emits approximately 5% of global, man-made CO₂ emissions. When all greenhouse gas emissions generated by human activities are considered, the cement industry is responsible for approximately 3% of global emissions.
Due to the unique nature of the product it manufactures, the cement industry currently emits 0.73 to 0.99 kilograms of CO₂ for every kilogram of cement produced. At any emission rate within this range, current proposals to curb CO₂ emissions will profoundly affect the activities and finances of the industry. Future proposals will likely call for far more significant reductions. Cement-related greenhouse gas emissions originate from fossil fuel combustion at cement manufacturing operations (about 40% of the industry’s emissions); transport activities (about 5%) and the combustion of fossil fuel that is required to make the electricity consumed by the cement manufacturing operations (about 5%). The remaining cement-related emissions (about 50%) originate from the manufacturing process that converts limestone (CaCO3) to calcium oxide (CaO), the primary precursor to cement. It is chemically impossible to convert CaCO3 to CaO, and then cement clinker, without generating CO₂. This CO₂ is currently emitted to the atmosphere.