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ECO-Concrete

INTRODUCTION

ECO- concrete is a revolutionary topic in the history of concrete industry. This was first invented in Denmark in the year 1998. ECO- concrete has nothing to do with color. It is a concept of thinking environment into concrete considering every aspect from raw materials manufacture over mixture design to structural design, construction, and service life.

ECO- concrete is very often also cheap to produce, because, for example, waste products are used as a partial substitute for cement, charges for the disposal of waste are avoided, energy consumption in production is lower, and durability is greater. ECO- concrete is a type of concrete which resembles the conventional concrete but the production or usage of such concrete requires minimum amount of energy and causes least harm to the environment.

The CO2 emission related to concrete production, inclusive of cement production, is between 0.1 and 0.2T per tonne of produced concrete. However, since the total amount of concrete produced is so vast the absolute figures for the environmental impact are quite significant.

Since concrete is the second most consumed entity after water it accounts for around 5% of the world‘s total CO2 emission .The solution to this environmental problem is not to substitute concrete for other materials but to reduce the environmental impact of concrete and cement.

The potential environmental benefit to society of being able to build with ECO- concrete is huge. It is realistic to assume that technology can be developed, which can halve the CO2 emission related to concrete production. With the large consumption of concrete this will potentially reduce the world‘s total CO2 emission by 1.5-2%. Concrete can also be the solution to environmental problems other than those related to CO2 emission.

It may be possible to use residual products from other industries in the concrete production while still maintaining a high concrete quality thus there is a large potential in investigating the possible use of these for concrete production. Well-known residual products such as silica fume and fly ash may be mentioned.

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ECO-Concrete

Environmental Goals

ECO- Concrete is expected to fulfill the following environmental obligations: Reduction of CO2 emissions by 21 %. This is in accordance with the Kyoto

Protocol of 1997. Increase the use of inorganic residual products from industries other than the

concrete industry by approx. 20%. Reduce the use of fossil fuels by increasing the use of waste derived fuels in

the cement industry. The recycling capacity of the ECO- concrete must not be less compared to

existing concrete types. The production and the use of ECO- concrete must not deteriorate the

working environment. The structures do not impose much harm to the environment during their

service life.

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ECO-Concrete

GENESIS

Considering the time elapsed since the commencement of the use of concrete, Eco- concrete is very young a material. It was invented in 1998 in Denmark. The increasing awareness and activity to conserve the environment and the realization that concrete production too releases a considerable amount of CO2 in the atmosphere were strong initiatives to catalyze the genesis of ECO- Concrete.

In 1997, the Kyoto Conference took place, in which several countries laid down several guidelines which would be the directive principles to the participating countries on their environment related practices. The guidelines( Kyoto Protocol) needed the countries to cut down their CO2 emissions to a certain degree as assigned. The given goal has to be achieved by the year 2012. Since then several countries started to focus on several available options but Denmark focused on cement and concrete production because approximately 2% of its total CO2

emission stems from cement and concrete production. Realizing the necessity of such a technology and the prospects associated, the Danish government soon released a proposal. The proposal covers the following environmental aspects: Greenhouse effect, Depletion of the ozone layer, Photochemical oxidation, Eutrophication, Acidification, Materials harmful to the environment and health, Water and resources. Five environmental impacts given highest priority are:

CO2 Energy Water Waste Pollutants

These, coupled with the cost reduction benefits allured the concrete producers to incorporate ECO-concrete into their paradigm.

Cement and concrete may have an important role to play in enabling the urban countries to fulfill their obligation to reduce the total CO2 emission by 21 % compared to the 1990-level before 2012, as agreed at the Kyoto conference. This is because the volume of concrete consumption is large. Approx. 1 m3 of concrete per capita are produced annually globally.

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The somewhat soft demands in the form of environmental obligations result in rather specific technical requirements for the industry - including the concrete industry. These technical requirements include among others new concrete mix designs, new raw materials, and new knowledge (practical experience and technical models) about the properties of the new raw materials and concrete mix designs.

On what ―measurement‖ basis can engineers and architects compare materials and choose one that is more sustainable or specify a material in such a way as to minimize environmental impact?

Life Cycle Assessment (LCA) seems to offer a solution. LCA considers materials over the course of their entire life cycle including material extraction, manufacturing, construction, operations, and finally reuse/recycling.

LCA takes into account a full range of environmental impact indicators—including embodied energy, air and water pollution (including greenhouse gases), potable water consumption, solid waste and recycled content just to name a few.

Building rating systems such as LEED and Green Globes are in various stages of incorporating LCA so that they can help engineers and architects select materials based on their environmental performance or specify materials in such a way as to minimize environmental impact.

Every 1 ton of cement produced leads to about 0.9 tons of CO2 emissions and a typical cubic yard (0.7643 m3) of concrete contains about 10% by weight of cement.

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ECO-Concrete

ADVANTAGES OF ECO-CONCRETE

ECO-concrete has manifold advantages over the conventional concrete. Since it uses the recycled aggregates and materials, it reduces the extra load in landfills and mitigates the wastage of aggregates. Thus, the net CO2 emissions are reduced. The reuse of materials also contributes intensively to economy. Since the waste materials like aggregates from a nearby area and fly ash

from a nearby power plant are not much expensive and also transport costs are minimal.

ECO-concrete can be considered elemental to sustainable development since it is eco-friendly itself. ECO-concrete is being widely used in green building practices. It also helps the green buildings achieve LEED and Golden Globe certifications.

Use of fly ash in the concrete also increases its workability and many other properties like durability to an appreciable extent. One of the practices to manufacture ECO-concrete involves reduction of amount cement in the mix, this practice helps in reducing the consumption of cement overall. The use waste materials also solve the problem of disposing the excessive amount industrial wastes.

There are several other advantages related to ECO-concrete and can be summarized as below:

Reduced CO2 emissions. Low production costs as wastes directly substitute the cement. Saves energy, emissions and waste water. Helps in recycling industry wastes. Reduces the consumption of cement overall. ECO-concrete is having good thermal and fire resistant. Better workability. Sustainable development. Greater strength and durability than normal concrete. Compressive strength and Flexural behavior is fairly equal to that of the

conventional concrete. ECO-concrete might solve some of the societies ‘problems with the use of

inorganic, residual products which should otherwise be deposited.

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METHODS TO PRODUCE ECO-CONCRETE

Desirable properties in ECO- concrete

Today, it is already possible to produce and cast very ECO- concrete. Even a super green type of concrete without cement but with, for example, 300 kg of fly ash instead can be produced and cast without any changes in the production equipment. But this concrete will not develop strength, and it will of course not be durable. Therefore, the concrete must include aspects of performance like:

Mechanical properties (strength, shrinkage, creep, static behavior etc.) Fire resistance (heat transfer, etc.) Workmanship (workability, strength development, curing, etc.) Durability (corrosion protection, frost, deterioration mechanisms, etc.) Environmental impact (how green is the new concrete?).

Meeting these requirements is not an easy task, and all must be reached at the same time if constructors are to be tempted to prescribe ECO- concrete. A constructor would not normally prescribe ECO- concrete if the performance is lower than normal, for example, a reduced service life.

Energy consumption during the production 1. Energy consumption in concrete mix design

The type and amount of cement has a major influence on the environmental properties of a concrete. An example of this is shown in Figure 2, where the energy consumption in mega joules/kg of a concrete edge beam through all its life cycle phases is illustrated.

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ECO-Concrete

The energy consumption of cement production make up more than 90% of the total energy consumption of all constituent materials and approximately one-third of the total life cycle energy consumption. By selecting a cement type with reduced environmental impact, and by minimizing the amount of cement, the environmental properties of the concrete are drastically changed. This must, however, be done while still taking account of the technical requirements of the concrete for the type and amount of cement.

One method of minimizing the cement content in a concrete mix is by using packing calculations to determine the optimum composition of the aggregate. A high level of aggregate packing reduces the cavities between the aggregates, and thereby the need for cement paste. This results in better concrete properties.

Another way of minimizing the cement content in a concrete is to substitute parts of the cement with other pozzolanic materials. It is common to produce concrete with fly ash and/or micro silica. Both of these materials are residual products (from production of electricity and production of silicon, respectively) and both have a pozzolanic effect.

Thus, a material with large environmental impact, i.e. the cement, is substituted with materials with reduced environmental impacts. Although there is no guideline given by the BIS on the addition of above components, the Danish Standards have laid down certain restrictions as given in Table 2.

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2. Energy consumption during cement and concrete production It is also possible to reduce the environmental impact of concrete by reducing the environmental impact of cement and concrete production. As regards concrete production, experience with the reduction of primarily water consumption, energy consumption and waste production is available. By selecting a cement type with reduced environmental impacts and by minimizing the amount of cement the concrete‘s environmental properties are drastically changed.

Evaluation of inorganic wastes

The materials, which have been judged as useable for concrete production and selected for further development, are listed below.It is based on an evaluation concerning both concrete tech. and environmental aspects. Inorganic residual products from the concrete industry (e.g. stone dust and concrete slurry) and products which pose a huge waste problem to society (e.g. combustion ash from water-purifying plants, smoke waste from waste combustion and fly ash from sugar production) have been given highest priority.

Stone dust- It is a residual product from the crushing of aggregates. It is an inert material with a particle size between that of cement and sand particles. Stone dust is expected to substitute part of the sand.

Concrete slurry-It is a residual product from concrete production, i.e. washing mixers and other equipment. It can be either a dry or wet substance, and can be recycled either as a dry powder or with water. In the case of dry material, it is necessary to process it to powder. The concrete slurry can have some pozzolanic effect, and might therefore be used as a substitute for part of the cement or for other types of pozzolanic materials such as fly ash.

Combustion ash from water-purifying plants-This type of combustion ash has the same particle size and shape as fly ash particles.

Smoke waste from waste combustion-It can have some pozzolanic effect. The content of heavy metals is significantly higher than that of ordinary fly ash. Furthermore, the content of chlorides, fluorides and sulphates can result in negative effects in connection with reinforcement corrosion, retardation and possible thaumasite reactions. Further processing will be necessary before its use in concrete.

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ECO-Concrete

Different ways to produce ECO-concrete

To increase the use of conventional residual products: To minimize the clinker content, i.e. by replacing cement with fly ash, micro silica in larger amounts than are allowed today.

By developing new green cements and binding materials, i.e. by increasing the use of alternative raw materials and alternative fuels, and by developing/improving cement with low energy consumption.

Concrete with inorganic residual products :(stone dust, crushed concrete as aggregate in quantities and for areas that are not allowed today) and cement stabilized foundation with waste incinerator slag, low quality fly ash or other inorganic residual products. Firstly, an information-screening of potential inorganic residual products is carried out. The products are described by origin, amounts, particle size and geometry, chemical composition and possible environmental impacts.

A pictorial representation of the methods is shown as below,

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ECO-Concrete

RESULTS OF STUDIES BASED ON REPORTED LITERATURE

ECO- Concrete containing Marble sludge powder and Quarry rock dust

A study on ECO-concrete replacing the conventional materials, except cement, with marble sludge powder and quarry rock dust.

1. Characterization of waste The physical characteristics of the waste are furnished in Table-3

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ECO-Concrete

2. Raw materials Cement: Ordinary Portland Cement (43 Grade) with 28 percent normal

consistency conforming to IS: 8112-1989 was used. Marble Sludge Powder: Marble sludge powder was obtained in wet form

directly taken from deposits of marble factories. It was observed that the marble sludge powder had a high specific surface area; thus it can confer more cohesiveness to mortars and concrete. Specific gravity of the marble sludge powder is 2.212.

Quarry rock dust: Its specific gravity is 2.677. Moisture content and bulk density of waste are less than the sand properties.

Fine aggregate: Medium size sand with fineness modulus = 2.20; Specific gravity 2.677, normal grading with the silt content 0.8%.

Coarse aggregate: Crushed stone with a size of 5-20 mm and normal continuous grading was used. The content of flaky and elongated particles is <3%, the crushing index ≤6% and the specific gravity 2.738.

Water: The qualities of water samples are uniform and potable. Super plasticizer: A super plasticizer,’Roff Superplast 320‘was used to get

and preserve the designed workability.

3. Mix proportion of concrete: For durability studies the IS mix proportion (by weight) use in the mixes of conventional concrete and ECO-concrete were fixed as (Cement: River sand/marble sludge + stone dust: coarse aggregate.) 1:1.81:2.04, 1:1.73:2.04 after several trials. Based on properties of raw materials, two different mix proportions were taken.

Mix A is the controlled concrete using river sand.Mix B is the ECO-concrete using industrial waste (50% quarry rock dust and 50% marble sludge powder) as fine aggregate.The water/cement ratio for both two mixes was 0.55% by weight. Water reducing admixture was used to improve the workability and its dose was fixed as 250 ml/50kg of cement.

4. Results and Discussion

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Workability:

Compressive and Split tensile strength: The 150 mm size concrete cubes, concrete cylinder of size 150 mm diameter and 300 mm ht. were used as test specimens to determine the compressive strength and split tensile strength respectively. The results of standard cubes and cylinders are compiled:

Durability and Resistance to Sulphate attack :The resistance to sulphate attack was studied by immersing the specimens in standard condition for 28, 90 days and 150 days in testing baths (containing 7.5 percent MgSO4 and 7.5 percent Na2SO4 by weight of water).

From results it was deduced that the durability of Green concrete under sulphate is higher to that of conventional concrete. This is due active SiO2 in marble powder and quarry rock dust can react with the Ca (OH)2 in concrete to form secondary calcium silicate hydrate and make it chemically stable and structurally dense, the impermeability of concrete is enhanced as well.In addition, the marble powder can reduce the content of calcium aluminates in cementitious material, leading to increase of sulphate resistance of concrete.

5. Conclusions

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ECO-Concrete

All the experimental data shows that the addition of the industrial wastes improves the physical and mechanical properties. These results are of great importance because this kind of innovative concrete requires large amounts of fine particles. Due to its high fineness of the marble sludge powder it provided to be very effective in assuring very good cohesiveness of concrete. From the above study, it is concluded that the quarry rock dust and marble sludge powder may be used as a replacement material for fine aggregate.

The chemical compositions of quarry rock dust and marble sludge powder are comparable with that of cement.

The replacement of fine aggregate with 50% marble sludge powder and 50% Quarry rock dust (Green concrete) gives an excellent result in strength aspect and quality aspect. The results showed that the M4 mix induced higher compressive strength, higher splitting tensile strength.

Green concrete induced higher workability and it satisfy the self compacting concrete performance which is the slump flow is 657mm without affecting the strength of concrete. Slump flow increases and V-funnel time decreases with the increase of marble sludge powder content.

Test results show that these industrial wastes are capable of improving hardened concrete performance.

Permeability of green concrete is less compared to that of conventional concrete.

The durability of green concrete under sulphate is higher to that of conventional concrete. From the results after 90-day immersion, the mortar specimens with green concrete in 7.5% sulphate solution have similar effect with those immersed for 28 days.

The combined use of quarry rock dust and marble sludge powder exhibited excellent performance due to efficient micro filling ability and pozzolanic activity. Therefore, the results of this study provide a strong recommendation for the use of quarry rock dust and marble sludge powder as fine aggregate in concrete manufacturing.

Behavior of Different Mixes to Different Environmental Classes

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ECO-Concrete

In another study to analyze the behavior of different compositions in various environmental classes several different mixes were prepared and exposed to different environmental conditions. The control parameters for the mixes were a slump of approximately 100 mm and, for the aggressive environment, an air content of 5.5%. The different green concrete mixes and their respective environmental conditions are tabulated as below:

Tables 8 and 9 show concrete mixes tested with high-volume fly ash for the passive and aggressive environmental classes. In the passive environmental class the fly ash content was increased from 24 to 70%, resulting in a reduction of CO2 emission from 18 to 57%. In the aggressive environmental class the fly ash content was increased from 9 to 40% resulting in a reduction of CO2 emission from 33 to 54%. AV5 is a modified version of AV4 with increased air content.Strength development is shown in Figures 4 and 5. The figures show that PV4, which has a fly ash content of 70%, has strength that is far too low: it appears that the fly ash content must not exceed approximately 60%. Even so, the strength

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ECO-Concrete

development is still too slow. As regards the concrete in the aggressive environmental class, the strength development is similar for all concrete types.

Passive: Dry atmosphere with no risk of corrosion. Aggressive: Moist atmosphere, with significant alkaline and/or chloride influence on the concrete surface or where there is risk of water saturation combined with frost.

Comparison between Conventional and Eco-Concrete

After enough development of ECO-concrete, the question arose about its relevance before conventional concrete. Lesser environmental impact was one thing but other properties like durability and resistance to fire etc were suspected and under study. Several tests thus carried out clearly showed that ECO-concrete was not a bad bargain indeed.

An environmental screening has been performed for a column presenting the different design principles as described below (green concrete columns defined as A, B, C). For comparison, the same environmental screening has been performed

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for a reference column (traditional concrete column defined as R), which is similar to column A, except that the green concrete type being substituted by a traditional concrete suitable for aggressive environment. The objective is to identify significant resource consumption and environmental loads of traditional concrete/design compared to ECO- concrete/design occurring during the entire service life, this includes the environmentally viewed most critical maintenance/repair stage. The performed lifecycle screenings quantify material usage (consumption of concrete) as well as CO2 emissions generated at the involved stages during the lifecycle of the columns.1): DENSIT® = Cement and micro silica based material providing high density and high compressive strength (150-300MPa)2): CRC® = Compact Reinforced Concrete which contains a high amount of steel fibre providing high ductility andCompressive strength (150-400 MPa)*) : without traditional waterproofing membrane**) : designation used for the environmental screening

The results of the environmental screening for the 3 green concrete columns (A, B, C) and the traditional concrete column (R) is presented in Table 11 with regard to the CO2-emission and in Table 12 with regard to the consumption of concrete.

This comparison demonstrates that column B (stainless steel reinforcement) and column C (stainless steel cladding) present the most environmental-friendly design solutions both with regard to the CO2 emissions and the consumption of concrete. An even more environmental-friendly solution is if the

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ECO-Concrete

LIMITATIONS OF GREEN CONCRETE

Although green concrete seems very promising when it comes to an environment friendly sustainable development, the prime concern is its durability. Denials are being constantly raised regarding the service life of structures made with green concrete. Further the split tension of green concrete has been found much less than that of conventional concrete. Another challenge before green concrete is that of a market. Until the properties of green concrete are at par with the conventional concrete, green concrete is unlikely to find many customers.

Several researchers have argued that green concrete can be made durable by using stainless steel reinforcements, but the predicament is that by using stainless steel concrete the cost of the construction increases considerably. Even after this, green concrete is not as durable as the conventional concrete. The limitations of using green concrete can be summarized as below:

By using stainless steel, cost of reinforcement increases. Structures constructed with green concrete have comparatively less life than

structures with conventional concrete. Split tension of green concrete is less than that of conventional concrete. Not as durable as conventional concrete.

Given these limitations coupled with the urgent need of reduction in green house gas emissions, has sparked off a number of researches across the globe to make green concrete more durable and bring it up to the mark with conventional concrete.

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SCOPE IN INDIA

Green concrete is a revolutionary topic in the history of concrete industry. Concrete is an indispensible entity for a developing country like India which desperately needs a continuously expanding infrastructure.

India is the second largest producer of cement in the world. Further India would be facing an exponential growth in the concrete demand by 2011.

Being produced in voluminous quantities in India, the concrete industry has a considerable part in the net CO2 emissions from the country. The net CO2

emissions from the construction agency are greater than any other industry.

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In order to act in a responsible manner towards a sustainable development of the nation, Green concrete is the need of the hour. India being a developing country produces concrete in enormous quantities which result in huge volumes of CO2

being emitted into the atmosphere each year. The total energy consumption (a rough estimate of the net CO2 emissions) during the manufacture of cement in India is tabulated as below:

The above statistics, though old, can be used as a guideline since the technological advancements have been scarce. As not much has been done and not much can be done to reduce these consumptions, the only alternative left is that of a green concrete, which will reduce the net CO2 emissions in the whole life cycle of concrete.

Thus we can deduce that, for a greener future, India needs to adopt Green concrete into practice as soon as possible. The other advantageous factor is its economy. As green concrete is made with concrete wastes and recycled aggregates, which are cheaper than conventional substitutes, and also with most of the industries facing problems with their waste disposal, put it out of the question to discard it.

Another type of green concrete, pervious concrete, when it comes to storm water management and rain water harvesting. Using pervious concrete we can easily tame the run-off and harness it for future uses in relatively dry areas, which would have otherwise drained away. With the alarmingly increasing cases of droughts each year pervious concrete would prove to be a utilitarian tool.

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CONCLUSIONs

The overview of the present state of affairs regarding concrete types with reduced environmental impact has shown that there is considerable knowledge and experience on the subject.

The somewhat vague environmental requirements that exist have resulted in a need for more specific technical requirements, and the most important goal is to develop the technology necessary to produce and use resource saving concrete structures, i.e. green concrete. This applies to structure design, specification, manufacturing, performance, operation, and maintenance.

Apart from several limitations coupled with the urgent need of reduction in green house gas emissions, has sparked off a number of researches across the globe to make green concrete more durable and bring it up to the mark with conventional concrete.

So definitely use of concrete product like GREEN CONCRETE in future will not only reduce the emission of CO2 in environment and environmental impact but also economical to produce.

The above facts clearly state a wide and promising scope of Green Concrete in the Near Future.

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REFERENCES:

www.google.com

Concrete Materials, DS 481:1998 [in Danish].

Greenlivingideas.com/.../can-concrete-be-eco-friendly/ - United States

en.wikipedia.org/wiki/Eco-cement

www.homeimprovementpages.com.au/.../eco_friendly_concrete

www.ecosmartconcrete.com/

www.eng.hokudai.ac.jp/COE-area/.../pdf/05aug11_hanehara.pdf

www.eco-serve.net/seminar/Programme-May.pdf