Engineering & Technology Review Article – 2
ECO-FRIENDLY
CONCRETE WITH HIGH VOLUME OF LAGOON ASH (Bapat J. D., Sabnis S.S.,
Hazaree C.V., Deshchaugule A. D., ASCE J. Materials in
Civil Engineering, Vol. 18, No. 3, 2006, pp 453-461)
*Principal,
AISSMS College of Engineering, Pune, email: jdbapat@yahoo.co.in
The majority of
the power production in India
and many developing countries comes from the thermal power plants,
using
pulverized coal as fuel. The non-combustible constituents of pulverized
coal
form the combustion residue or ash. The finer fraction of ash,
entrained in the
flue gas, which gets collected in the electrostatic precipitator, is
referred
as fly ash (FA). The part of the ash that falls at the bottom of the
boiler in
the form of hot clinker is known as bottom ash. As a general practice
in India and many
other countries, FA and bottom ash are mixed with water and transported
to ash
ponds/lagoons. The ash deposited in lagoons is called lagoon ash or
pond ash. The
ash lying in these lagoons occupies huge cultivable land besides posing
a
serious environmental threat. In India, for example, the ash lagoons
cover more than 40,000 ha. of land. The ash lying in lagoons contains
significant amount of moisture, carbon particles and shows a large
variation in
the particle size, chemical and mineralogical composition and hence not
used in
concrete.
The research
investigation reported in the paper was conducted to develop a concrete
with
high volume of lagoon ash, with a view to finding a possible approach
to
mitigate this environmental problem.
The test
specimens were prepared with 55 and 65 % lagoon ash and compared with
concrete
containing 55 and 65 % fly ash of good quality, collected from the
electrostatic precipitators. The lagoon ash used in the experiment did
not
satisfy the requirements of national standard for its use in concrete.
The authors
propose the use of lagoon ash in dry lean concrete (DLC) below pavement
quality
concrete in case of concrete roads. The mixture proportion of DLC made
in the
laboratory using 55 % lagoon ash passed the Indian Road Congress
criteria of
average 10 MPa strength at 7 days. The quantity of lagoon ash required
will be
about 319 t/km for a 4/6 lane highway, considering 150 mm thickness of
DLC. The
large-scale use of lagoon ash in concrete shall contribute towards
solving the
problem of environmental pollution and help the sustainable development
of both
thermal power generation and concrete construction. The Ministry of
Road
Transport and Highways, Government of India, has undertaken
construction of
National Highways on a massive scale. The Portland cement concrete will
be
extensively used for the construction.