IAETSD

1. Green concrete
Eco-friendly construction
M.SASIDHAR
Dept. of Civil Enginering
SMVEC
Puducherry, India
sasidharm007@gmail.com
V.SUNDARKISHNAN
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.
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.
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.
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.
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.
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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2. 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 by-
products 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%.
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 by-
products 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
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.
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 by-
product 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.
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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3.  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.
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.
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.
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.
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.
REFERENCES:
[1] www.greenconcrete.info
[2] http://greenglobe.com/
[3] http://flyash.sustainablesources.com
[4] http://www.microsilica-china.com
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