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.

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).

Geosynthesis of Rock-based Geopolymer cements was the objective of the European multidisciplinary BriteEuram industrial research project GEOCISTEM. The project titled cost effective GEOpolymeric Cements for Innocuous Stabilization of Toxic EleMents, in short GEOCISTEM, started on Jan. 1994 and has been completed on June 1997.

In J. Davidovits’ book, Geopolymer Chemistry & Applications, Chapter 10 is dedicated to Rock-based Geopolymer cements.

The project seek to manufacture economical geopolymeric cements primarily for the long-term containment of hazardous and toxic wastes and for restoring sites highly contaminated with uranium mining waste (the WISMUT sites in former East Germany). The patented GEOPOLYTECH® process is currently undergoing industrial testing on various sites. In the recently updated book Geopolymer Chemistry & Applications this application is outlined in Chapter 26. You may also go to the Geopolymer Library and download several papers.

Rock-based Geopolymer cements are manufactured in a different manner than Portland cement. Geopolymeric cements do not require high temperature kilns, or large expenditures of fuel, nor do they require such a large capital investment for the plant and equipment. Thermal processing at temperatures not higher than 600-700°C of naturally occurring alkali-silico-aluminates and alumino-silicates (geological resources available on all continents) provides suitable rock-based geopolymeric raw-materials.

In addition, the GEOCISTEM technology reduces the energy consumption of manufacturing cement. The global introduction of these low-CO₂ geopolymeric cements, for civil engineering, infrastructure and general construction purposes will reduce the CO₂ emissions created by the cement concrete industry by 80%. This can mitigate overall Global Warming .

Partners:

• European Commission, Brussels
• B.R.G.M. Bureau de Recherches Géologiques et Minières (France)
• CORDI-GEOPOLYMERE SA (France)
• LAVIOSA CHIMICA MINERARIA SPA (Italy)
• CAGLIARI UNIVERSITY, Dpt Scienze della Terra (Italy)
• BARCELONA UNIVERSITY, Facultat de Geologia (Spain)

Sub-contrators for Cordi-Geopolymere SA, Saint-Quentin:

• WISMUT GmbH, Chemnitz (Germany)
• HEIDELBERGER ZEMENT AG, Heidelberg (Germany)
• NAMUR University, Namur (Belgium)
  CEMENTI BUZZI, Torino (Italy)
• CAEN UNIVERSITY, Centre Etude et Recherche sur l’Antiquité (France)
• Project leader: Prof. Dr. Joseph Davidovits, Cordi-Geopolymere SA

Acid Resistant Concrete for Uranium and Metallic Mining Sites

Metallic mine tailings are usually generating sulphuric acid that results from the oxidation of pyrite. The resistance to strong sulphuric acid solution (5% H₂SO₄ solution) was investigated after the standard 28 days of hardening. Testing involved comparative sand mortar standard methods with Portland cement (type I 42.5 R from our sub-contractor Cementi Buzzi) and a geopolymeric cement that comprises 75% by weight of geological elements. This cement is coined CARBUNCULUS cement because of it similarity with the calcined pozzolan “carbunculus”, which according to the Roman architect Vitruvius (1st Century AD) was the basic material of the good Roman mortar (see in Archaeo-Analogues and also the paper #D Searching for Carbunculus ). After 60 days, CARBUNCULUS cement remains practically intact whereas the acid corrosion has destroyed more than 65% of Portland Cement I.42.5 (weight loss and change in shape and volume).

Comparative test CARBUNCULUS cement vs. Portland cement I.42.5, 28 days of hardening. Weight loss after 7, 28 and 60 days in Sulphuric acid solution (5%, pH=0).

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.