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.
However, 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. 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. And as it is known that 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.
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%.
· 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 are
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.