“ Optimization of Fly Ash Bricks for Sustainable
Construction ”
, FLY ASH: AN OVERVIEW
Fly ash is the by-product of coal combustion collected by the
mechanical or electrostatic precipitator (ESP) before the flue
gases reach the chimneys of thermal power stations in very large
volumes. All fly ash contain significant amounts of silicon
dioxide (SiO2), aluminium oxide (Al2O3), iron oxide (Fe2O3),
calcium oxide (CaO), and magnesium oxide (MgO) however, the
actual composition varies from plant to plant depending on the
coal burned and the type of burner employed. Fly ash also
contains trace elements such as mercury, arsenic, antimony,
chromium, selenium, lead, cadmium, nickel, and zinc.
These particles solidify as microscopic, glassy spheres (fig.1) that
are collected from the power plant’s exhaust before they can
―fly ۅaway — hence the product’s name: Fly Ash. Chemically,
fly ash is a pozzolan. When mixed with lime (calcium hydroxide),
pozzolans combine to form cementitious compounds.
The power requirement of the country is rapidly increasing with
increase in growth of the industrial sectors. India depends on
Thermal power as its main source (around 65% of power
produced is thermal power), as a result the quantity of Ash
produced shall also increase.
Indian coal on an average has 30% to 40% Ash and this is one of
the prime factors which shall lead to increased ash production and
hence, Ash utilization problems for the country.
Fly ash is one of the numerous substances that cause air, water
and soil pollution, disrupt ecological cycles and set off
environmental hazards. It’s also contains trace amounts of toxic
metals which may have negative effect on human health and on
plants and the land where the fly ash decomposed not gets reused.
, The disposal of this waste material is a matter of great concern
from the environmental and ecological point of view. The safest
and gainful utilization of this material has been one of the topics
of research over the last few decades.
The advantages of fly ash utilization are:
• Saving of space for disposal and natural resources.
• Energy saving and Protection of environment.