2. introduction
The consumption of natural aggregates of all types has
been increasing in recent years in most countries owing to
rapid industrialization.
Due to increased construction activities in India,
availability of natural fine aggregates are depleting by
each passing day. The continued extraction of natural
aggregates leads to serious environmental problem
including landslides.
Using industrial waste products as either cement additives
or alternate fuels, it is possible to reduce the quantity of
raw materials and fossil fuels used to produce cement.
3. The use of industrial by-products diverts the material from
the waste stream, reduce the energy used in processing
virgin materials, use of virgin materials and decreases
pollution.
Besides industrial waste offering environmental
advantages, it also improves the performance (HSC and
HPC) and quality of concrete which is the need of hour for
most problems of 21st century including Earthquake
resistance and Durability.
4. Utilization in concrete – a best alternative since it uses up
Fly ash, Red mud, Silica fume, Rice-husk ash or GGBS for
OPC.
It helps to put off Global Warming but utilizes the waste
materials efficiently thereby reducing the risk of waste
disposal and at same hand, safeguards dwindling natural
resources.
The role of a Civil Engineer is to reduce cement
consumption through the use of supplementary materials.
Hoping this simple initiative will add water to the burning
fire and it will kindle the spirit of young Civil Engineers to
use eco-friendly construction materials in this present
scenario.
5. Materials used
Most common materials that can be used in concrete are
Fly Ash
Ground Granulated Blast furnace Slag (GGBS)
Red Mud
Microsilica
Metakaolin
Rice Hush Ash (RHA)
6. Fly ash - non-combusted by-product of coal-fired power
plants. During combustion, the coal's mineral impurities
such as clay, feldspar, quartz and shale fuse in suspension
and are carried away from the combustion chamber by the
exhaust gases. Such fused material cools and solidifies into
spherical glassy particles called fly ash. Fly ash is a finely
divided powder resembling Portland cement consisting
mostly of SiO2.
Red mud - major industrial waste by Bayer process for
the extraction of alumina. Characterized by strong
alkalinity due to presence of excessive amount of
dissolved NaOH. The red color is by the oxidized Fe
present, which can make up to 60% of mass of the red
mud. In addition to Fe, the other dominant particles
include silica, unleached residual Al, and TiO .
7. Disposal becomes a huge problem due to the presence of
high pH, heavy metals and radioactivity. Hence new
technologies utilizing red mud are gently needed, besides
the use in of GPC.
Kaolinite - clay mineral with the chemical composition
Al2Si2O5(OH)4, which means each particle has one
tetrahedral silica layer and one octahedral alumina layer.
It is a soft mineral produced by the chemical weathering of
aluminum silicate minerals like feldspar. Rocks that
arerich in Kaolinite are also known as china clay, white
clay, or kaolin. Metakaolin is a dehydroxylated form of the
clay mineral Kaolinite in the temperature range of 500-
800°C. It is a highly pozzolanic.
8. Ground-granulated blast-furnace slag (GGBS) - obtained
by quenching molten iron slag from a blast furnace in
water or steam, to produce a glassy, granular product that
is then dried and ground into a fine powder. The main
components of blast furnace slag are CaO (30-50%), SiO2
(28- 38%), Al2O3 (8-24%) and MgO (1-18%). GGBS has
now effectively replaced sulfate-resisting Portland cement
(SRPC) on the market for sulfate resistance because of its
superior performance and greatly reduced cost compared
to SRPC.
9. Silica fume - also known as microsilica, is an amorphous
polymorph of silicon dioxide, silica. It is an ultrafine
powder collected as a by-product of the silicon and
ferrosilicon alloy production. It 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 which
makes it suitable as pozzolanic material for high
performance concrete.
10. Rice husk Ash (RHA) - Rice husk also called rice hull, is
the hard protecting covering of grains of rice, which is a
by-product generally obtained from milling process of rice.
The RHA is generated after burning the rice husk in the
boiler, which is collected from the particulate collection
equipment. It is highly porous, lightweight and contains
silica in high content (90 – 95%). At present, disposal of
RHA is dumping on waste land, creating land dereliction
problems. Since amount of RHA generated is in plenty, an
effective way of disposal of RHA is needed urgently.
11. FLY ASH RED MUD METAKAOLIN
GGBS
MICROSILICA
RHA
12. From the literature reviews it is concluded that,
Micro silica can be added at a rate of 5-15% by weight of
cement
Red Mud can be used up to 30%.
Fly Ash and GGBS can be used upto 100% in GPC
RHA can be replaced upto 20%.
The performance of various by-products in concrete can
be listed as follows
conclusion
13. Material Flyash
Workability Enhanced
Compressive
Strength
Increase with age
Split Tensile
Strength
Increased as fineness of fly ash increased
Modulus of
Elasticity
Higher than conventional concrete
Material Redmud
Workability Improved due to low moisture absorption of Red Mud
Compressive
Strength
Increased upto 30%
Split Tensile
Strength
Similar to that of compressive strength
Modulus of
Elasticity
No effect
14. Material metakaolin
Workability Better
Compressive
Strength
Improved upto 40%
Split Tensile
Strength
Improved upto 40%
Modulus of
Elasticity
Increases with increase in Metakaolin content
Material GGBS
Workability Improved
Compressive
Strength
Reduction at early age
Split Tensile
Strength
Slightly higher
Modulus of
Elasticity
No effect
15. Material microsiica
Workability Increased upto 10%
Compressive
Strength
Increase upto the level of 7.5%
Split Tensile
Strength
Increase upto the level of 7.5%
Modulus of
Elasticity
Increase with increase in Microsiica content
Material RHA
Workability Less than 20% replacement shows decreased Workability
Compressive
Strength
Highest value is expected at 20%
Split Tensile
Strength
Enhanced performance
Modulus of
Elasticity
Decreased as addition of RHA decreased
16. references
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