GREEN CONCRETE

By:Abhinav Srivastava3rd B. Tech. Civil Engg. February 2011

OVERVIEW OF THE PRESENTATION In this presentation on Green Concrete, I

would be discussing about the following aspects of green concrete.

1. Introduction2. Genesis3. Advantages4. Production5. Results of studies based on reported

literature6. Limitations7. Scope in India8. Conclusions

INTRODUCTION Green concrete is a revolutionary topic in the

history of concrete industry. This was first invented in Denmark in the year 1998. 

Green 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.

Green concrete has nothing to do with colour.

BACKGROUND Since concrete is the second most consumed entity after

water it accounts for around 5% of the world’s total CO2 emission.

The CO2 emission related to concrete production, inclusive of cement production, is between 0.1 and 0.2 t per tonne of produced concrete.

Though these figures might seem to be minute but owing to the voluminous quantities of concrete produced each year, these figures attain a colossal amount.

Further, due to increasing eco-awareness, the concrete producers needed a new technology that would reduce the environmental impact of concrete rather than switching to some substitute to it.

Other GHGs; 14.80

De-forestation; 3.94

Fossil Fuels; 23.90

Concrete Industry; 1.40

Global Green house gas emissions in year 2000 (Gt of CO2 equivalents)

ENVIRONMENTAL GOALS Reduction of CO2 emissions by 21 %.

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 green concrete must not be less compared to existing concrete types.

The production and the use of green concrete must not deteriorate the working environment.

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

GENESIS The increasing awareness and activity to conserve the

environment and the realisation that concrete production too releases a considerable amount of CO2 in the atmosphere were strong initiatives to catalyse the genesis of Green Concrete.

In 1997, the Kyoto Protocol was signed which required the countries to cut down their CO2 emissions as assigned.

After this, Denmark focused on cement and concrete production because approximately 2% of Denmark’s total CO2 emission stems from cement and concrete production.

Cement and concrete may have an important role to play in enabling the developed countries to fulfil their obligation to reduce the total CO2 emission by 21 % compared to the 1990-level before 2012, as agreed at the Kyoto conference.

A typical cubic yard (0.7643 m3) of concrete contains about 10% by weight of cement. There have been a number of articles written about reducing the CO2 emissions from concrete primarily through the use of lower amounts of cement and higher amounts of supplementary cementitious material (SCM) such as fly ash and slag, which is using green concrete.

Due to growing interest in sustainable development engineers and architects were motivated more than ever before to choose concrete that is more sustainable.

ADVANTAGES OF GREEN CONCRETE

Green concrete has manifold advantages over the conventional concrete.

Reduces CO2 emissions, saves energy and waste water.

Since it uses the recycled aggregates and materials, it reduces the extra load in landfills and mitigates the wastage of aggregates.

Economy.

Elemental to sustainable development since it is eco-friendly itself.

Helps in reducing the consumption of cement overall.

The use waste materials also solve the problem of disposing the excessive amount industrial wastes.

Green concrete might solve some of the societies’ problems with the use of inorganic, residual products which should otherwise be deposited.

Use of fly ash in the concrete also increases its workability and many other properties like durability to an appreciable extent.

PRODUCTION OF GREEN CONCRETE

DIFFERENT METHODS OF GREEN CONCRETE PRODUCTION

residual

products from other industries

• sewage sludge. incineration ash

• stone dust, concrete slurry

• combustion ash from water purifying plants

Supplement-ary cementitiou-s

materials

• large qty of fly ash and microsilica

• GGBS

cement with

reduced environmenta

l impact

• mineralised cement

• limestone addition

Green concrete =conventional cement+coarse aggregate+……

RESULTS OF STUDIES BASED ON REPORTED LITERATURE - I

Green Concrete containing Marble sludge powder and Quarry rock dust

Sample Code

Moisture Content (%)Bulk

Density (kg/m3)

Fineness modulus

Effective size (mm)

Coefficient of

uniformityCoefficient

of gradation

Wet Dry          Marble sludge powder

23.35 1.59 1118 2.04 0.17 1.58 1.37

Quarry rock dust 24.25 2.1 1750 2.35 0.22 4.5 2.2

Sand 25 2.5 1430 2.2 0.2 6 2

In 2009, M. Shahul Hameed and A. S. S. Sekar, conducted a study on green concrete replacing the conventional materials, except cement, with marble sludge powder and quarry rock dust.

In the table below, the physical properties of marble sludge and quarry dust are compared to that of sand.

Mix proportion of concrete was 1:1.81:2.04 (Mix A: control) and 1:1.73:2.04 (Mix B: green concrete) and water/cement ratio for both mixes was kept 0.55.

THE RAW MATERIALS USED WERE Cement: OPC (43 Grade) with 28% normal consistency and specific

surface 3300 cm2/g.

Marble sludge powder: It had a high specific surface area. Specific gravity of the marble sludge powder is 2.212.

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

Fine aggregate: Modulus of fineness = 2.20; Specific gravity 2.677

Coarse aggregate: Crushed stone with a size of 5-20 mm. Flakiness within limits.

Water: Potable

Super plasticizer: ‘Roff Superplast 320’ was used to get and preserve the designed workability.

RESULTSWorkability Comparisons

Mix Slump in mm Slump flow in mm V-funnel time in sec

Mix A (Control) 210 420 23

Mix B (Green concrete)

255 657 14

Compressive and Split tensile strength

Mix

Average Compressive Strength in N/mm2

Split Tensile Strength in N/mm2

3 Days 7 days 28 days 3 days 7 days 28 days

Mix A (Concrete)

15.45 18.33 36.85 2.40 2.60 4.62

Mix B (Green

Concrete)13.54 19.52 40.35 2.15 2.98 5.02

In addition, the marble powder can reduce the content of calcium aluminates in cementitious material, leading to increase of sulphate resistance of concrete.

Durability and Resistance to Sulphate attack

Mix

% of water absorption

after 28 days

Percentage of weight loss

28 days 90 days 150 days

Na2SO4

and MgSO4

H2SO4

Na2SO4

and MgSO4

H2SO4

Na2SO4

and MgSO4

H2SO4

Mix A (Control)

2.85 1.65 2.10 2.20 2.65 2.95 3.15

Mix B (Green

concrete)3.74 1.15 0.80 1.95 1.10 2.10 1.80

CONCLUSIONS 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.

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.

The water absorption of green concrete is slightly higher than conventional concrete.

The durability of green concrete under sulphate is higher to that of conventional concrete.

RESULTS OF STUDIES BASED ON REPORTED LITERATURE - II

Behaviour of different mixes to different environments.

Control PV1 PV2 PV3 PV4

Cement Content(kg) 148 120 101 85 61

Content of Fly Ash (%) 24 50 50 60 70

Content of Micro Silica (%) 6 - 6 6 6

CO2 reduction - 18 31 41 57

Water/Cement 0.71 0.78 0.80 0.70 0.74

Five different concrete mixes were prepared with one as control.Their mix proportion is as shown below in the table:

The fly ash content was increased from 24 to 70%, resulting in a reduction of CO2 emission from 18 to 57%.

These mixes were then subjected to a passive environment and their strength development was analyzed.

Passive signifies dry atmosphere with no risk of corossion.

STRENGTH DEVELOPMENT IN PASSIVE ENVIRONMENT

48 168 672 13440

5

10

15

20

25

30

35

ControlPV1PV2PV3PV4

Time (h)

Com

pres

sive

Str

engt

h (M

Pa)

Six different concrete mixes were prepared with one as control.Their mix proportion is as shown below in the table:

Control AV1 AV2 AV3 AV4 AV5

Cement Content(kg) 309 274 272 219 190 189

Content of Fly Ash (%) 9 9 18 30 40 40

Content of Micro Silica (%) 5 5 5 5 5 5CO2 reduction - 33 33 46 54 54

Water/Cement 0.37 0.421 0.42 0.42 0.42 0.42

The fly ash content was increased from 9 to 40% resulting in a reduction of CO2 emission from 33 to 54%.

These mixes were then subjected to a aggressive environment and their strength development was analyzed.

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.

STRENGTH DEVELOPMENT IN AGGRESSIVE ENVIRONMENT

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10

20

30

40

50

60

70

ControlAV1AV2AV3AV4AV5

Time (h)

Com

pres

sive

Str

engt

h (M

Pa)

INFERENCES 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 development is still too slow. As regards the concrete in the aggressive environmental class, the strength development is similar for all concrete types. However, preliminary testing indicates that the high-volume fly ash concrete might have problems with frost resistance.

LIMITATIONS OF GREEN CONCRETE

The cardinal concern is its durability.

By using stainless steel, cost of reinforcement increases.

Split tension of green concrete is less than that of conventional concrete.

Susceptible to frost action.

The other important concern is the quantification of green concrete emissions.

SCOPE IN INDIA

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.

India would be facing an exponential growth in the concrete demand by 2011.

Cement Demand (Mt/annum)

Year GDPtotal GDPindustry GDPconstruction GDPaverage

2001 103.0 107.6 106.2 105.6

2006 139.5 148.7 150.8 146.3

2011 186.9 204.2 210.4 200.5

THE NET CO2 EMISSIONS FROM THE CONSTRUCTION AGENCY ARE GREATER THAN ANY OTHER INDUSTRY.

Other Indus-tries,

62.70%Production of materials for construction;

10.90%

Transportation for construc-tion; 5.00%

Construction work; 1.30%

Operation of building, 10.20%

Operation of business facilit-

ies, 9.90%

India being a developing country produces concrete in gargantuan quantities which result in huge volumes of CO2 being emitted into the atmosphere each year.

In order to act in a responsible manner towards a sustainable development of the nation, Green concrete is the need of the hour.

The total energy consumption (a rough estimate of the net CO2 emissions) during the manufacture of cement in India is tabulated as below:

Fuel Units 1991-92 1992-93 1993-94Electricity GWh 4800.52 6420.97 6754.60

Coal Mt 10.8 11.7 11.1Petroleum Products

Mt 0.293 0.296 0.291

Total Cement

ProductionMt 53.6 54.1 58.0

The other advantageous factor is 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.

The above facts clearly state a wide and promising scope of Green Concrete in the near future in our country.

CONCLUSIONS

The presentation has given us an overview of the green concrete.

The urgency in the environmental matters have forced us to resort to the resource saving and eco-friendly practices. Green concrete fulfills both the criteria.

It is realistic to assume that the technology can be developed, which can halve the CO2 emission related to concrete production, and with the large energy consumption of concrete and the following large emission of CO2 this will mean a potential reduction of total CO2 emission by 2%.

The net emission from a typical ton of concrete emits 0.1 to 0.2 ton of CO2 .

So whatever way one looks at it focusing on just the production of concrete accounts for a very small percent of overall CO2 emissions.

However one should keep in mind that whatever CO2 emission reductions that are possible will still account for at best a 2% global CO2 reduction (assuming a challenging 21% reduction in global CO2 emissions).

Thank You