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Nature reflects our nature
Green Concrete
Concrete is the second most consumed
material in this world. Concrete consists of fine
aggregates (sand) and coarse aggregates (rocks,
gravels) bonded together by cement which hard-
ens over time giving strength to the composite
structure. It was first used around 700 BC by
Nabatean traders who discovered the properties
of hydraulic lime with self-cementing properties.
After that, it wasn’t used much until the 18th cen-
tury when British Engineer John Smeaton built
Smeaton Tower using concrete. Since then, its
use skyrocketed up to the point that it became
the second most consumed material after water
in this world.
It is used practically in every structure mainly
because of properties like workability, high com-
pressive strength and tensile strength (only when
coupled with steel reinforcements), fire
resistance which makes it useful in making hous-
es, buildings, dams, monuments, etc. It is esti-
mated that around 10 billion tons of concrete is
produced annually.
Although concrete is vital to physical infrastruc-
ture and overall development of human beings,
it has also harmful effects on the environment
that need to be addressed. Concrete needs ce-
ment and it is estimated that the cement industry
ALONE contributes to a whopping 8% all world-
wide C0 2 emissions. Nearly 900 kg of CO 2 are
emitted for every 1000 kg of Portland cement
produced. Besides this, cement industries also
emit heavy metals into the air which can cause
severe health problems and air pollution.
Besides cement, concrete damages the most fer-
tile layer of the earth, the topsoil by creating hard
surfaces which leads to surface runoff, soil ero-
sion, water pollution and flooding. It also causes
urban heat island effect, which is the case when
urban areas become warmer compared to
surrounding rural areas.
When it comes to producing environmentally
friendly concrete, the major aims are to reduce
CO 2 emissions, usage of fossil fuels during pro-
duction, usage of harmful mixtures in the con-
crete, savings in use of cement through substi-
tution by other materials, and recycling concrete/
cement.
Green Concrete is environment friendly concrete
which improves three pillars of sustainability: en-
vironmental, economic and social. The key fac-
tors that are used to identify if concrete is green
are amount of portland cement replacement
materials, manufacturing process and methods,
performance and life cycle sustainability impacts.
This can be done with the help of nanoengineer-
ing.
For example, concrete’s strength and durability
lies in the organization of spherical nanoparti-
cles, calcium silicate, which when stacked in
pyramids reaches a high density. If we can find
particles other than calcium silicate hydrates that
will pack in high densities without the burning,
that’s quite the invention. Some have identified
that magnesium could be an alternative to calci-
um silicate hydrates.
Reduction of energy during cement production is
one of the ways to make concrete greener. For
example, Utilization of inorganic polymers (geo-
polymers) in sustainable concrete is one method
which has smaller CO 2 emissions compared to
Portland Cement. Similarly, Urban waste (munic-
ipal solid waste) can be used for the manufac-
ture of concrete. They relate to the utilization of
waste in a sustainable manner and can reduce
CO 2 emissions.
Despite different methods developed in the field
of green concrete usage, green concrete faces
barriers like construction business practice, un-
willingness of consumers, building codes, lack of
a holistic approach in engineering education and
research, etc. However, if our resources are to
be conserved and used sustainably, convention-
al concrete should be considerably reduced and
use of green concrete should be strived towards
for.
Sushant Dahal
B.E Civil,
3rd Year( Batch-2016)
Nature and Social Concern Society
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