ISBN: 378-26-138420-01
INTERNATIONAL CONFERENCE ON CURRENT TRENDS IN ENGINEERING RESEARCH, ICCTER - 2014
Green concrete Eco-friendly construction M.SASIDHAR
V.SUNDARKISHNAN
Dept. of Civil Enginering SMVEC Puducherry, India sasidharm007@gmail.com
Dept. of Civil Engineering SMVEC Puducherry, India sundarakishnan14@gmail.com
Abstract— This paper explains about CO2 emissions in concrete and it’s remedy as green concrete and the materials used for manufacturing green concrete.
II. REDUCTION OF CO2 EMISSION The potential environmental benefit to society of being able to build with green 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. During the last few decades society has become aware of the deposit problems connected with residual products, and demands, restrictions and taxes have been imposed.
Index Terms— CO2 emission , fly ash , microsilica
I. 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 has nothing to do with colour. 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. Green 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. 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. The CO2 emission related to concrete production, inclusive of cement production, is between 0.1 and 0.2 t per tonne of produced concrete.
III. RAW MATERIALS FOR GREEN CONCRETE Several residual products have properties suited for concrete production, 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. The concrete industry realised at an early stage that it is a good idea to be in front with regard to documenting the actual environmental aspects and working on improving the environment, rather than being forced to deal with environmental aspects due to demands from authorities, customers and economic effects such as imposed taxes. Furthermore, some companies in concrete industry have recognised that reductions in production costs often go hand in hand with reductions in environmental impacts. Thus, environmental aspects are not only interesting from an ideological point of view, but also from an economic aspect.
I. PROBLEMS IN CONVENTIONAL CONCRETE Since the total amount of concrete produced is so vast the absolute figures for the environmental impact are quite significant, due to the large amounts of cement and concrete produced. Since concrete is the second most consumed entity after water it accounts for around 5% of the world‘s total CO2 emission (Ernst Worrell, 2001). The solution to this environmental problem is not to substitute concrete for other materials but to reduce the environmental impact of concrete and cement. Pravin Kumar et al, 2003, used quarry rock dust along with fly ash and micro silica and reported satisfactory properties.all fonts, in particular symbol fonts, as well, for math, etc.
A. RECYCLED MATERIALS IN GREEN CONCRETE: The production of cement used in concrete results in the creation of greenhouse gases, including CO2. The U.S.
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ISBN: 378-26-138420-01
INTERNATIONAL CONFERENCE ON CURRENT TRENDS IN ENGINEERING RESEARCH, ICCTER - 2014
reaches its maximum strength more slowly than concrete made with only portland cement. The techniques for working with this type of concrete are standard for the industry and will not impact the budget of a job. This section also addresses wall-form products. Most of these products have hollow interiors and are stacked or set in place and then filled with steel-reinforced concrete creating a concrete structure for a house. Some wall-form materials are made from EPS (expanded polystyrene) which is a lightweight non-CFC foam material. There are also fiber-cement wall-form products that can contain wood waste. The EPS/concrete systems offer high insulating qualities and easy installation. The fiber-cement blocks offer insulating qualities as well. Some EPS products also have recycled content.
cement industry has reduced CO2 emissions by 30% since 1972 and now accounts for approximately 1.5% of U.S. emissions, well below other sources such as heating and cooling homes and buildings (33%), truck and auto use (27%) and industrial operations (19%). The CO2 embodied in concrete as a finished building product is a very small quantity considering that cement accounts for a small proportion of the finished product. The concrete industry also uses industrial waste byproducts such as fly ash (from coal combustion) and blast furnace slag (created in iron manufacture) to constitute a portion of the cement used in producing concrete. Use of such by-products in concrete prevents 15 million metric tons a year of these waste materials from entering landfills. Utilizing these "supplemental cementitious materials" as a replacement for cement improves the strength and durability of concrete and also further reduces the CO2 embodied in concrete by as much as 70%, with typical values ranging from 15% to 40%.
C. SILICA FUME: Silica fume, also known as microsilica, is an amorphous (non-crystalline) polymorph of silicon dioxide, silica. It is an ultrafine powder collected as a byproduct of the silicon and ferrosilicon alloy production and consists of spherical particles with an average particle diameter of 150 nm. The main field of application is as pozzolanic material for high performance concrete. It is sometimes confused with fumed silica. However, the production process, particle characteristics and fields of application of fumed silica are all different from those of silica fume. Silica fume is an ultrafine material with spherical particles less than 1 μm in diameter, the average being about 0.15 μm. This makes it approximately 100 times smaller than the average cement particle. The bulk density of silica fume depends on the degree of densification in the silo and varies from 130 to 600 kg/m3. The specific gravity of silica fume is generally in the range of 2.2 to 2.3. The specific surface area of silica fume can be measured with the BET method or nitrogen adsorption method. It typically ranges from 15,000 to 30,000 m2/kg.
Finally, when a concrete structure has served its purpose, it can be crushed for use as aggregate in new concrete or as fill or base materials for roads, sidewalks and concrete slabs. Even the reinforcing steel in concrete (which often is made from recycled materials) can be recycled and reused. B. FLY ASH: Fly ash is one of three general types of coal combustion by-products (CCBP’s). The use of these byproducts offers environmental advantages by diverting the material from the wastestream, reducing the energy investment in processing virgin materials, conserving virgin materials, and allaying pollution. Thirteen million tons of coal ash are produced in Texas each year. Eleven percent of this ash is used which is below the national average of 30 %. About 60 – 70% of central Texas suppliers offer fly-ash in ready-mix products. They will substitute fly-ash for 20 – 35% of the portland cement used to make their products. Although fly-ash offers environmental advantages, it also improves the performance and quality of concrete. Fly ash affects the plastic properties of concrete by improving workability, reducing water demand, reducing segregation and bleeding, and lowering heat of hydration. Fly ash increases strength, reduces permeability, reduces corrosion of reinforcing steel, increases sulphate resistance, and reduces alkali-aggregate reaction. Fly ash
ENVIRONMENTAL GOALS: Green Concrete is expected to fulfil 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%.
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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.
There are several other advantages related to green concrete and can be summarized as below: a) Reduced CO2 emissions. b) Low production costs as wastes directly substitute the cement. c) Saves energy, emissions and waste water. d) Helps in recycling industry wastes. e) Reduces the consumption of cement overall. f) Better workability. g) Sustainable development. h) Greater strength and durability than normal concrete. i) Compressive strength and Flexural behaviour is fairly equal to that of the conventional concrete. j) Green concrete might solve some of the societies problems with the use of inorganic, residual products which should otherwise be deposited.
ADVANTAGES OF GREEN CONCRETE: Green 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. Green concrete can be considered elemental to sustainable development since it is eco-friendly itself. Green concrete is being widely used in green building practices.
CONCLUSION: The newer the technologies simultaneously it must be eco-friendly. Using Green concrete in Construction field is a revolution for the eco-friendly civil infrastructural development. Upcoming generation must use the green concrete instead of conventional concrete so that CO2 emission is considerably reduced.
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 green 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.
REFERENCES: [1] [2] [3] [4]
www.greenconcrete.info http://greenglobe.com/ http://flyash.sustainablesources.com http://www.microsilica-china.com
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