19-09-2012, 01:26 PM
FLY ASH BRICKS
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INTRODUCTION :
Pulverized fuel ash commonly known as fly ash is a useful by-product from thermal power stations using pulverized coal as fuel and has considerable pozzolonic activity. This national resource has been gainfully utilized for manufacture of pulverized fuel ash-lime bricks as a supplement to common burnt clay buildings bricks leading to conservation of natural resources and improvement in environment quality.
Pulverized fuel ash-lime bricks are obtained from materials consisting of pulverized fuel ash in major quantity, lime and an accelerator acting as a catalyst. Pulverized fuel ash-lime bricks are generally manufactured by intergrading blending various raw materials are then moulded into bricks and subjected to curing cycles at different temperatures and pressures. On occasion as and when required, crushed bottom fuel ash or sand is also used in the composition of the raw material. Crushed bottom fuel ash or sand is also used in the composition as a coarser material to control water absorption in the final product. Pulverized fuel ash reacts with lime in presence of moisture from a calcium hydrate which is a binder material. Thus pulverized fuel ash – lime in presence of moisture form a calcium – silicate hydrate which is binder material. Thus pulverized fuel ash – lime brick is a chemically ended bricks.
MARKET DEMAND:
180 billion tones of common burnt clay bricks are consumed annually approximately 340 billion tones of clay- about 5000 acres of top layer of soil dug out for bricks manufacture, soil erosion, emission from coal burning or fire woods which causes deforestation are the serious problems posed by brick industry. The above problems can be reduced some extent by using fly ash bricks in dwelling units.
Demand for dwelling units likely to raise to 80 million units by year 2015 for lower middle and low income groups, involving an estimated investment 0f $670 billion, according to the Associated chamber of commerce and industry. Demand for dwelling units will further grow to 90 million by 2020,which would requires a minimum investment of $890billion. The Indian housing sector at present faces a shortage of 20million dwelling units for its lower middle and low income groups which will witness a spurt of about 22.5million dwelling units by the end of Tenth plan period. There is ample scope for fly ash brick and block units.
In Chennai alone 1 crore bricks are required for constructional activities in every day. But good quality of bricks as well as required quantity are not available moreover during the rainey seasons supply of clay bricks are very difficult. Therefore, in order to fulfill the required demand there will be a great chance to start more units in the field of fly ash bricks.
RAW MATERIALS
Fly Ash s the inorganic mineral residue obtained after burning of coal/lignite in the boilers. Fly Ash is that portion of ash which is collected from the hoppers of ESP’s and pond ash is collected from the ash ponds. Bottom ash is that portion of ash which can be collected fro the bottom portion of the boilers. The characteristics of fly ash depend upon the quality of lignite/coal and the efficiency of boilers.
India depends upon primarily on coal for the requirement of power and her power generation is likely to go up from 60,000MW in the year 2010. While generation of power from bituminous sources is on increase. The generation of fly ash is also likely to increase. The fly ash generation in India Thermal Stations is likely to shoot up to 170 million tones in 2010 from the present level of 100 million tones. The disposal of fly ash in the present method will be a big challenge to environment, especially when the quantum increases from the present level.