The “pulverized fuel ash” (PFA) or the so-called fly ash
(FA), used as a mineral admixture in cement and concrete, is a product of the
pulverized coal firing system, through conventional boilers, mostly used in the
thermal power plants. While carbon burns in oxidizing surroundings, the inorganic
mineral matter gets sintered and liquefied at high temperature. The melt flows
down the walls of the furnace and about 25% gets collected as “bottom ash”
(BA). It is crushed before disposal. The rest, PFA or FA, gets entrained in the
up-flowing hot gas in the form of fine particles, which get trapped in the
economizer, air-preheater, mechanical separator, and, finally, battery of
electrostatic precipitators (ESP).
As a general practice in many countries, PFA and BA are
mixed with water and transported to ash ponds/lagoons. The ash thus deposited
in lagoons is called “lagoon ash” (LA) or “pond ash.” It causes problems besides
occupying huge stretches of agricultural land. Notwithstanding the greater
utilization of PFA (and BA) in recent times in cement and concrete, in bricks,
and for land filling, a large quantity of ash still lies unutilized. It is now well established that replacing cement with fly ash improves long term strength and durability.
As per several estimates, the cement industry
contributes about 5% of the global generation of carbon dioxide. The cement
industry’s sustainable program developed by the World Business Council for
Sustainable Development (WBCSD) prepared an “Agenda for Action” for a 5 year
period from 2002 to 2007, endorsed by the leading cement manufacturers of the
world. The agenda addressed the issues of (a) climate protection, (b) fuels and
raw materials use, and (c) emission reduction besides other issues.
Written
for engineers, book focuses on making more workable and durable concrete using
mineral admixtures. For each mineral admixture, book looks at manufacturing and
processing, physical characteristics, chemical and mineralogical composition,
quality control, and reported experiences. It also examines the provisions of
national standards.It encourages engineers to more effectively use these and
other wastes in cement and concrete to support more sustainable growth of
industry. Buy
this book online to obtain 20 % discount and free shipping. Download details:
http://bit.ly/online_purchase
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