PRESENTED BY ARCHANA MALLICK 8 TH SEM CIVIL ENGG.

INTRODUCTION  Green concrete is made with industrial wastes which make it eco-friendly.  The concept of “Green Concrete“ was first originated in Denmark in the year 1998 by Centre for Resource Saving Concrete Structures.  The CO 2 emission related to concrete production, inclusive of cement production, is between 0.1 and 0.2 t per tonne of produced concrete.  From cement and concrete production a total quantity of 6,00,000-1,200,000 t CO 2 per year is emitted.  The solution to this environmental problem is not to substitute concrete for other materials but to reduce the environmental impact of concrete and cement.

HOW TO PRODUCE? This can be divided into two groups:  Concrete mix design:  cement with reduced environmental impact  minimizing cement content  substituting cement with pozzolanic materials such as fly ash and microsilica  Cement and concrete production:

1.CEMENT WITH REDUCED ENVIRONMENTAL IMPACT  The cement industry contributes about 5% to global CO 2 emissions, making the cement industry an important sector for CO 2 -emission mitigation strategies.  CO 2 is emitted from the calcination process of limestone, from combustion of fuels in the kiln, as well as from power generation.  Emission mitigation options include energy efficiency improvement, new processes, a shift to low carbon fuels, application of waste fuels.

2.MINIMIZING CEMENT CONTENT  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 a better environmental profile, due to a smaller amount of cement.

3.SUBSTITUTING CEMENT WITH POZZOLANIC MATERIALS SUCH AS FLY ASH AND MICROSILICA  Another way of minimizing the cement content in concrete is to substitute parts of the cement with other pozzolanic materials.  Both of these materials are residual products and both have a pozzolanic effect.

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. AGGREGATE CONSERVATION  It has been estimated that annually roughly 1 billion tonnes of concrete and masonry rubble is generated.  At present, only small quantities of aggregate derived from recycled concrete and masonry are being used.  Recycled-concrete aggregate, particularly the recycled masonry aggregate, has a higher porosity than natural aggregate.

WATER CONSERVATION  Fresh, clean water is getting more and more scarce every day.  As one of the largest industrial consumers of fresh water, it’s imperative for the concrete industry to use water more efficiently.  Most recycled industrial waters or even brackish natural waters are suitable for making concrete. This is even more true for curing water.  Large savings in curing water can be realized by the application of textile composites.

PRODUCTION OF GREEN CONCRETE  Three different ways to produce green concrete:  concrete with minimal clinker content.  concrete with green types of cements and binders.  concrete with inorganic, residual products.

INORGANIC RESIDUAL PRODUCTS Numerous residual products have been discussed below: 1. Stone dust Stone dust is a residual product from the crushing of aggregates. It is an inert material. Stone dust is expected to substitute part of the sand.

2. Concrete slurry Concrete slurry is a residual product from concrete production, i.e. washing mixers and other equipment. The concrete slurry is can be either a dry or wet substance and can be recycled either as a dry powder or with water. 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.

3. Combustion ash from water-purifying plants  This type of combustion ash has the same particle size and shape as fly ash particles.  The content of heavy metals in the slurry is expected to be approximately at the same level as for fly ash.  The 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.

4. Smoke waste from waste combustion This smoke waste can have some pozzolanic effect. The content of heavy metals is significantly higher than that of ordinary fly ash. 5. Fly ash from sugar production The fly ash from this source is not expected be very different from ordinary fly ash.

RESULTS OF INVESTIGATIONS INTO GREEN CONCRETE  Compressive and Split tensile Strength MIX Average In Compressive N/mm 2 StrengthAverage Strength Split In Tensile N/mm 2 3 Days 7 Days28 Days 3 Days 7 Days 28 Days MIX A MIX B

 Workability MIX Slump in mm Slump flow in mm V-funnel time in sec MIX A MIX B

 Durability studies To investigate the water absorption, permeability and resistance to sulphate attack for both conventional concrete and green concrete. 1.Water Absorption MIX % of water absorption after 28 days MIX A 2.85 MIX B 3.74

2. Permeability MIX Impermeable Pressure(MPa) Description Depth OfPenetration Min(in cm)Max(in cm) MIX A 2.0 No leakage found MIX B 2.0 No leakage found

3.Resistance to sulphate attack

 CO 2 emissions for different designs of concrete columns Design solution Column R Column A Column B Column C Traditional Concrete Traditional Design+ Green concrete Stainless steel reinforcement + green concrete Stainless steel cladding + green concrete kg CO 2 per year

MOTORWAY BRIDGE IN DENMARK

STAINLESS STEEL REINFORCEMENT

ADVANTAGES  30% CO 2 reduction  20% residual products as aggregate  New types of residual products used  No environmental pollution and sustainable development  Good thermal and fire resistant  Permeability is less compared to that of conventional concrete  Durability of concrete is higher than that of conventional concrete  Higher workability

CONCLUSION  During the last few decades society has become aware of the deposit problems connected with residual products.  It may be possible to use residual products from other industries in the concrete production while still maintaining a high concrete quality.  The aggregates required for such type of green concrete is available worldwide yet its utilization is still limited.  Due to the benefits of green type concrete it appears to offer a promising way to sustainable environment in developing countries.  Finally, I would like to close with a quote from the German poet Goethe :“Knowing is not enough, we must practice; willingness is not enough, we must act.”

REFERENCES     ‘ Green’ Concrete in Denmark by M. Glavind and C. Munch-Petersen,Concrete Centre, Danish Technological Institute, Denmark  Utilization of hazardous wastes and by-products as a green concrete material by Smita Badur and Rubina Chaudhary.  Environmentally “Green” Concrete Structures by Dr.-Ing. Carola Edvardsen and M.Sc. Karsten Tølløse

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