Geopolymer Concrete

DURABILITY OF STRUCTURE

REPORT of GEOPOLYMER CONCRETE

GREEN CONCRETE Tu T. Nguyen

December 2009

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I. Introduction This subject points out a view of material behaviour, particularly behaviour of concrete. As well

as fresh concrete technology has advanced at a pace similar to many other aspects of concrete

technology over the past three decades, and indeed many these advances have been inner-

dependent. For example, the availability of super-plasticizer has enabled workable concrete to

be produced at lower water/binder ratio thus increasing the strength.

In this paper, one report will be concerned with objective, principle and durability of structure

with its potential in application.

II. Specification With the increasing concern of the natural resources and environment, new technologies have

been developed or are under developing in construct materials, particularly, in concrete.

This paper requires submitting a research report to give an overview on these technologies. An

example of any one particular technology should be provided to find out advantage and

disadvantage of objective, principles, what is the effect on durability and sustainability of

structure with potential in application.

There is no limit on the topics. For example, it could be high performance concrete for particular

application, self compacting concrete, or the concrete used to abate CO2, etc.

III. Overview on application of advanced concrete technology Concrete is the world’s most important construction material. However, an abundance of raw

material such as rock, gravel, sand and water in the concrete reaches approximately 75-90%

produced annually in North European countries (Concrete for the environment, 2003).

Therefore, the quality of concrete does not reach a necessary compressive strength. It is a

reason for new technologies which should be discovered. At the same time, the world is tackling

global warning and resources problem. New concrete technologies are an environmentally

friendly material and are – when correctly produced and used very durable as a consequence.

Structures at the ends of their lives can be demolished and recycled as aggregate in new

concrete or for road construction. Hence, there are some of these advanced concrete

technologies to examine in this paper.

- Development of a Sustainable Concrete Waste Recycling System - Application of Recycled

Aggregate Concrete Produced by Aggregate Replacing Method (Yasuhiro Dosho) (Journal of

Advanced Concrete Technology, Volume 5.1 (2007): In this paper, the research showed the

reuse of construction waste is highly essential from the viewpoint of Life Cycle Assessment

(LCA) and effective recycling of construction resources. Therefore, a promotion of the reuse of

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construction waste is necessary to achieve three basic concepts: (1) assurance of safety and

quality, (2) decrease of environmental impact, and (3) increase of cost effectiveness of

construction. This paper outlines the development of a recycling system, application of recycled

aggregate concrete produced by the aggregate replacing method, which is effective in reducing

both cost and environmental impact from the viewpoint of LCA for concrete waste generated by

the demolition of large-scale buildings. Result of this study showed that the adoption of the

developed recycling system was confirmed to recycle concrete waste produced from the

demolition buildings in a highly effective manner reducing both recycling cost and environmental

impact.

- Geopolymer concrete technology (Dr. Erez Allouche) (Sciencedaily, 2009): This research is

led by an assistant professor of civil engineering at Louisiana Tech University and associate

director of the Trenchless Technology Center. In this paper, the research outlines a comparison

between old concrete (Portland cement concrete (PCC)) and new concrete based Inorganic

polymer concrete (geopolymer) in pumping carbon dioxide (CO2) into our atmosphere. The

research showed the geopolymer will contribute lower CO2 than the PCC do. In addition,

geopolymer concrete (GPC) features greater corrosion resistance, substantially higher fire

resistance (up to 2400° F), high compressive and tensile strengths, a rapid strength gain, and

lower shrinkage in comparison to ordinary Portland cement.

- Danish Experiences with a Decade of Green Concrete (Claus Vestergaard Nielsen and Mette

Glavind) (Journal of Advanced Concrete Technology, Volume 5.1 (2007)): This research points

out a comparison of the Danish cement and concrete industry over last ten years. A reduction of

Portland clinker content, which means improved amount of CO2 in the concrete, was involved in

this area. Absorption of CO2 from the atmosphere was described in this 3-year project. It is the

result of several scientific investigations for instance determining the effect of concrete

emissions on the air quality and the solution to hydrocarbon pollution in concrete slurry at the

concrete plant. Finally the article contains examples of how to improve the sustainability of

concrete production and how to produce green concrete. Green concrete is the term used in

Denmark for environmentally friendly concrete production and structures.

- High strength concrete (Bill Price) (Newman J. and Choo B.S, 2003):

The water/cement ratio is main cause for the strength of the paste. However, the paste’s

strength depends on the porosity, because of the fragment size distribution of the crystalline

phases and in-homogeneities within the hydrated paste.

Therefore, this technology outlines a new method will manufacture a newly mixture of concrete

with higher strength by a reduction in water/cement ratio as a consequence of less capillary

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porosity in the paste. A reduction of capillary porosity also supports the structure of fine-textured

hydration products which have a higher strength than the previous concrete. In addition, the

capillary porosity can be decreased by evaluating the particle size distribution of the

cenemetitious materials in order to increase the potential packing density.

IV. Choice of research report Concrete and its constituent parts are available and used globally. It has been, is, and will

continue to be the major construction material for mankind. As a consequence, we have a

responsibility for concrete's effective design, construction and efficient use. Future resources,

energy consumption, performance, durability, environmental and social impacts as well as

economies are all importance ons which concrete’s sustainability will be evaluated - and this

has a global significance. Increasingly, both political and practical levels, construction has to

address and implement sustainability and towards this goal. However, Portland cement

production, which is popular use in the global, is a major contributor to carbon dioxide (CO2)

emissions. It has pumped into the atmosphere about five to eight percent of all human-

generated atmospheric CO2 worldwide. Production of Portland cement is currently toping 2.6

billion tons per year worldwide and growing at 5 percent annually (Erez Allouche, 2009).

In comparison to ordinary Portland cement (OPC), geo-polymer concrete (GPC) features

greater corrosion resistance, substantially higher fire resistance (up to 2400° F), high

compressive and tensile strengths, a rapid strength gain, and lower shrinkage. Perhaps Geo-

polymer concrete's greatest appeal is its life cycle greenhouse gas reduction potential; as much

as 90% when compared with OPC (Erez Allouche, 2009).

In addition, as a considerable concern of the world when the world runs out resource and deals

with global-warming, using concrete as a construction material actually helps us protect natural

resources and offers consumers benefits that are not available with other building products such

as steel or wood. In an area of increased attention to the environmental impact of construction

and sustainable development, concrete has much to offer. Therefore, in this paper, geo-polymer

concrete or “Green concrete” as an advanced concrete technology is reported to estimate

positive and negative effect of this technology on environment and resources. The new

technology is being concerned by human-being in the future, with objective and principle to

provide the effects on durability and sustainability of structure with its potential in application.

Geo-polymer concrete has additionally the potential for basically reducing CO2 emissions,

producing a more durable infrastructure capable of design life. It has a long life circle in

comparison with Portland cement concrete about hundreds of years instead of tens (Erez

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Allouche, 2009). Particularly, it can self-protect aquifers and surface bodies of fresh water via

the elimination of fly ash disposal sites.

V. Characteristic of Geoplymer concrete V.1 Principle The term “geopolymer” was invented by Davidovits in 1978. This inorganic aluminosilicate

polymer is synthesized from predominantly silicon and aluminium material of geological origin or

by-product materials such as fly ash, chemicial composition of geopolymer materials are similar

to Zeolite. (R.Malathy (n.d.)).

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.

V.2 The chemical composition The first chemical element in the geo-polymer founded in 1970 is the aluminosilicate kaolinite

reacts with NaOH at 100°C-150°C and polycondenses into hydrated sodalite (a tecto-alumino-

silicate), or hydro-sodalite (Davidovits, 2002):

Si2O5,Al2(OH)4 + NaOH ⇒ Na(-Si-O-Al-O)n

kaolinite hydrosodalite

The polymerisation process involves a substantially fast chemical reaction under alkaline

condition on Si-Al minerals, those results in a three dimensional polymeric chain and ring

structure consisting of -Si-O-Al-O- bonds, as follows:

Mn [-(SiO2) z–AlO2] n.wH2O

Since n is the degree of poly-condensation, M is predominantly a monovalent cation (K+, Na+),

althought Ca2+ may replace two monovalent cations in the structure (Davidovits J., 1999). In

the same result, Davidovits pointed out that although the SiO2/Al2O3 ratio given by z is 1, 2 or 3

for the sialate-siloxo and sialate-disloxo-chains, even z can be higher than 3 (up to 32). This can

be exaplained by cross linking of poly-silicate chains with a silicate link (-Si-O-Al-O-) bonds

(Figure 2).

Therefore, the geo-polymer material diagram can be shown as described by equations below

(Edward G. Nawy, 2008):

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Figure 1 – Geo-polymer backbone and geo-polymer precursor

Edward shows the formation of geo-polymer materials is shown in the first equation in figure 1,

it is not clear since setting and hardening of geo-polymer precursor. Therefore, in terms of the

second equation (geo-polymer backbone) shown in figure 1, water is released during the

chemical bonds. The water removed from the geo-polymer matrix during the curvature. This is

completely different from Portland cement concrete mixture during the hydration process.

Hence, there are 2 main constituents of geo-polymer which are the source materials and the

alkaline liquids. The most common alkaline liquid used in geo-polymerisation is a combination of

sodium hydroxide (NaOH) or potassium hydroxide (KOH) and sodium silicate or potassium

silicate.

Figure 2 Geo-polymer molecular networks

V.3 Material Materials includes fly-ash (FA), sand Aggregates (SA), alkaline liquid (AL), water (W), super-

plasticizer (SP). In the batches of fly ash, the molar Si-to-Al ratio was about 1-3. A combination

of sodium silicate solution and sodium hydroxide solution was chosen as the alkaline liquid. The

sodium hydroxide (NaOH) solution was prepared by dissolving either the flakes or the pellets in

water. The mass of NaOH solids in a solution varied depending on the concentration of the

solution expressed in terms of molar, M. sand is small Aggregates in geo-polymer mortar. To

improve the workability of the fresh geo-polymer mortar, super-plasticizer was used in most of

the mixtures (Nguyen and Bui and Dang, 2008).

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Figure 3: The beginning of the geo-polymers phase development on the surface of the fly ash

particle V.4 Setting time of geo-polymer mortar Types of fly ash, composition of alkaline liquid and ratio of alkaline liquid to fly ash by mass are

the factor during setting time of geo-polymer mortar. However the most important factor is the

curing temperature. The figure below shows curing temperature has a significant effect on a

similarity of setting time between initial setting-time and final setting-time.

Figure 4 Effect of curing temperature on setting time (Nguyen and Bui and Dang, Recent

Research Geo-polymer Concrete, 2008)

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Figure 5: Room temperature setting for concrete made of geo-polymer cements and Portland cements. (Geo-polymer: Inorganic Polymeric New Materials, Journal of Thermal Analysis, Vol

37, Davidovits, 1991) V.5. Compressive strength

As a highly above, GEO-polymer concrete has a major difference from Portland cement

concrete is the binder (Edward G. Nawy, 2008). The silicon and aluminium oxides in the low-

calcium fly ash react with the alkaline liquid to form the geo-polymer paste that binds the loose

coarse aggregates, fine aggregates and other did not react materials together to form the geo-

polymer concrete. As in case of Portland cement concrete, the coarse and fine aggregates

occupy about 75% to 80% of the mass of geo-polymer concrete.

Figure 6: Fly ash before reacting with alkaline liquid

Figure 7: Fly ash after reacting with alkaline liquid

Therefore, the compressive strength and workability of geo-polymer concrete are influenced by

the proportions and properties of the constituents that make the geo-polymer paste.

Experiment results (Hardjito and Rangan, 2005)

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- In terms of molar a higher concentration of the sodium hydroxide sodium results in the

higher compressive strength of geo-polymer concrete.

- The higher ratio of sodium silicate solution to sodium hydroxide solution by mass results

in the higher compressive strength of geo-polymer concrete.

- The addition of naphthalene-sulfonate-based super-plasticizers, up to 4% of fly ash by

mass, improves the workability of fresh geo-polymer concrete. However, there is a slight

degradation in the higher compressive strength of geo-polymer concrete of harden

concrete when the super-plasticizers dosage is greater than 2%.

- The slump value of the fresh geo-polymer concrete increases when the water content of

the mixture increases.

- The H2O/Na2O molar ratio increases, the compressive strength of geo-polymer concrete

decreases.

- The effect of the Na2O/Si2O molar ratio on the compressive strength of geo-polymer

concrete is insignificant.

Figure 8: Effect of water-to-polymer solids ratio by mass on compressive of geo-polymer

concrete. (Hardjito, D. and Rangan, B. V. Development and Properties of Low-Calcium Fly

Ash-based Geopolymer Concrete, Research Report GC1, Faculty of Engineering, Curtin

University of Technology, Perth, 2005)

As can be seen from the above, compressive strength depends on curing time and curing

temperature. As the curing time and curing temperature increase, the compressive strength

increases. Curing temperature in (600C- 900C), curing time in (24h-72h), compressive strength

400-500 kG/cm2 as shown in figures below.

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Figure 9 - Extra water effects

Figure 10 - Effect of curing temperature

Figure 11 - Curing time effect

Figure 12 Effects of saturated water specimens

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V.6 Corrosion resistance The corrosion resistance of geo-polymer concrete is similar to this property of geo-polymer

cement. Geo-polymer concreted has been excellent properties within both acid and salt

environments since limestone has not used as a material in concrete. It is especially suitable for

tough environmental conditions. The geo-polymer concrete can be become bend when it is in

sea water environment. This can be useful in marine environments and on islands short of fresh

water; in contrast Portland cement concrete is impossible in sea water.

Two grades of AAFG concretes were prepared for this investigation. G54 represents a

Geopolymer concrete synthesised at high temperature (12 hours at 70°C) whereas G71 was

achieved at ambient. They were used in resistance of corrosion in Fly Ash based Geo-polymer

concrete research by X. J. Song, M. Marosszeky, M. Brungs, R. Munn.

As can be seen in Figure 11, the binder in the normal PC55 concrete shows significant

degradation the aggregate becoming exposed after only 4 weeks in 10% sulphuric acid. By

contrast, Geo-polymer concrete cubes, G71 and G54, remained structurally intact in the same

acidic environments after 56 days, though some very fine localised cracks were observed (X. J.

Song, 2005)

Figure 13: Appearance of concrete specimens exposed in 10% sulphuric acid (Left: PC55 for 28

days, right: AAFG for 56 days) (X. J. Song, M. Marosszeky, M. Brungs, R. Munn, 2005)

The samples are indicated that AAFG concrete is durable in 10% sulphuric acid up to 56 days

by Song. In case of Portland concrete, the hydration compounds were naturalised by sulphuric

acid and dramatically the binder disintegrated.

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Figure 14 Mass change in 10% sulphuric acid

(X. J. Song, M. Marosszeky, M. Brungs, R. Munn, 2005)

The samples have a low mass loss (figure 12) of Geo-polymer concretes in this research. This view is similar to Davidovit (1990) and Rostami and Brendley (2003). The compressive strength was used in this research to evaluate the impact of acid attack on

mechanical performance. Although the strength reduction (Figure 13) was significant within the

first week of immersion, this trend then became stable with residual strength up to 33 ~ 42 MPa

after 56 days acid exposure (X. J. Song, M. Marosszeky, M. Brungs, R. Munn, 2005).

Figure 15 Compressive strength change of AAFG concretes in 10% sulphuric acid

In addition, there is very interesting to compare the acid resistance between G54 and G71. a

significant difference has shown in the 28 days strength development in the research. As

expected, G54 has higher compressive strength than G71 due to the effect of higher

temperature curing. However, both of them have a very similar trend in resisting sulphuric acid

attack, in terms of mass change (Figure 12), compressive strength reduction (Figure. 13).

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Therefore AAFG concretes are acid resistant regardless of curing conditions. It also seems that

Geopolymer concretes have the potential to be used in the production of pre-cast sewer pipes

(high temperature curing) as well as in the repair of corroded pipes.

VI. Geo-polymer concretes and the Green-house Global-warming challenge According to the research of Davidovits in 1991, CO2 emissions resulting from chemical

reactions will continue to increase with industrial development. This is specifically the case for

Portland cement manufacturing. Cement results from calcinations of limestone (calcium

carbonate) and silico-alumnious material according to the reaction:

5CaCO3 + 2SiO2 = (3CaO,SiO2)(2CaO,SiO2) + 5CO2 [1]

The production of 1 tons cement generates 0.55 tons of CO2 and needs the burn of carbon-fuel

into 0.42s of CO2. To simplify: 1T cement = 1T CO2. However, The production of 1 tone of Geopolymeric cement generates 0.180 tones of CO2, from combustion carbon-fuel, compared

with 1.00 tones of CO2 for Portland cement. Geo-polymeric cement generates six times less

CO2 during manufacture than Portland cement. This simply means that, in newly industrialising

countries, six times more cement for infrastructure and building applications might be

manufactured, for the same emission of green house gas CO2. (Davidovits J, 2002). Indeed,

Geopolymeric cement only requires the calcinations at 800°C for two geological ingredients,

Carbunculus and KANDOXI. High furnace slag is a by-product that no longer needs any

subsequent treatment. In addition, it is the processing of the development carried out on

inorganic alumino-silicate polymers or geo-polymers (Davidovits, 1985), resulting from the geo-

polymeric reaction:

2Si2O5.Al2O2 + K2(H3SiO4)2 + Ca(H3SiO4)2 = (K2O.CaO)(8SiO2.2Al2O3.nH2O [2]

The equation [2] release less CO2 emission than the first equation. Therefore, geo-polymer

concrete is more “green” than Portland cement concrete.

VII. Advantages and disadvantages of Geopolymer concrete VII.1.Advantages Fristly, This is one of the primary advantages of geopolymers over traditional cements from an

environmental perspective is largely associated with releasing much lower CO2 emission than

Portland cement. This is mainly due to the absence of the high-temperature calcinations step in

geopolymer synthesis.

Secondly, Geo-polymer concrete offers several economic benefits over Portland cement

concrete. The price of a ton of fly ash is only small fraction of the price of a ton of Portland

cement; therefore, after allowing for the price of the alkaline liquids required making the geo-

polymer concrete, the price of fly-ash-based geo-polymer concrete is estimated to be about 10

to 30% of Portland cement concrete. Furthermore, the very little drying shrinkage, low creep,

excellent resistance to sulphate attack, and good acid resistance offered by the heat-cured, low-

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calcium, fly-ash-based geo-polymer concrete may yield additional economic benefits when it is

used in infrastructure application.

The other factor is geopolymer concrete offers increase resource efficiency by producing

concrete products with longer services lives.

Corrosion resistance and high strength of geo-polymer are other factors. Geo-polymer concrete

still keeps high compressive strength after mass loss and resisting from acid attack.

VII.2 Disadvantages Regardless of all these positive attributes, geo-polymer concrete is finding it hard to enter the

modern market today. A main reason is because large cement companies are basically scared

that the profit margins go down and financial risk. Another reason, the cost of geo-polymer is

major factor. It is more expensive than Portland cement about 60% per cubic meter. (Cement 

and Concrete Research, Pacheco, Torgal et al., p 93).

In the construction industries view, “green cement” has yet to establish itself as a viable, just

recognised or proven technology (Cement and Concrete Reseach, vol 37, p1591, Duxson et al,

2007).

VIII. Conclusion Construction and concrete industry have been utilising a tremendous amount of resources and

energy. Therefore, they have a responsibility to reduce environmental impacts in their activities.

For the concrete industry to contribute to the sustainable development of mankind, it is

necessary to promote technical development for further reduction of environmental impacts. To

promote this, it will be necessary to introduce environmental design systems based on

environmental performance, develop environmental performance evaluation tools and construct

systems for their actual application.

It is obvious that the concrete sector also has to consider the reduction of environmental

impacts in their technologies towards the sustainable development of human beings. The new

century of concrete technologies is beginning with geo-polymer concrete. It releases lower

carbon dioxide than traditional concrete. Geo-polymer offers many advantages in durability of

structure such as increase of corrosion resistance, high compressive strength. Geo-polymer

also has a high economic effect in concrete market today.

In future, national and global environmental laws in regards to C02 emissions should force the

Portland cement and concreting companies to convert to use ‘green cement’.

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