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Policy
perspective on Fly ash utilization in clay
brick making Fly ash is a waste material obtained during the burning of pulverized coal in thermal power plants. It is a potential raw material for use in heavy clay structural processes and products. The potential utility of fly ash as a building material has received wide attention for the manufacture of burnt clay based bricks, cement concrete, light weight aggregates, fly ash lime bricks and so forth. The utilization of fly ash in land filling, brick making, road making and use as pozzolana are some of the major avenues available for the use of fly ash in India. Ministry notification The Ministry of Environment and Forests through its notification published in the Gazette of India, Part II, Section 3, sub section (ii) vide S.O. 763(E) dated 14 September, 1999 issued directives for proper utilization of fly ash discharged from coal or lignite based thermal power plants. Recognizing the importance for restricting the excavation of top soil for manufacture of bricks and promoting the utilization of fly ash in the manufacture of building materials and in construction activity, it was notified to compulsory utilize 25% by weight of fly ash in burnt clay fired brick making within a radius of 100 km from a coal or lignite based thermal power plant. Fly ash characteristics Fly ash is a waste / by product of coal burning thermal power plants. Fly ash is composed of loose fine-grained material that is mostly amorphous in nature with a small percentage of crystalline matter. The chemical composition of fly ash depends on the coal source and the material. Indian fly ash is generally high in silica and alumina and low in calcia. The nature of fly ash also varies with the point of collection in the power plant. Amorphous opaque and non-opaque particles with angular geometry are obtained at low temperatures, angular particles with rounded vesicular structures are obtained at intermediate temperature and at the highest temperatures, spherically shaped solid, cenospheric and pleospheric particles are obtained. Scientific work conducted Utilization of fly ash as a resource has been studied for decades in many areas such as in valuable element extraction, in environmental engineering, in ceramic products, in agriculture, in paint and plastic industry, in building products (brick, cement, aggregate, concrete). Still, the utilization amount is very low. A major factor preventing utilization is the difficulty of producing quality – controlled fly ash materials that can meet market specifications. Present status
The present demand of
burnt clay bricks in India is assessed to be 140 billion per year. With
increased emphasis and need of Use of ash (specifically bottom ash) within the bricks will also reduce the specific energy consumption to the tune of approximately 20%. This will not only reduce the external coal consumption, but also save precious energy. Besides the energy scenario, the negative impact of the brick industry includes the loss of topsoil. According to one estimate 80,000 to 1, 00,000 acres of good agricultural land is wasted per year in India for providing clay for brick making. Use of fly ash can reduce this topsoil use again to the tune of 20% - 30%. Advantage of soil substitution by fly ash is that the red colour of the bricks is preserved whereas the quality is improved. At present the main obstacles towards usage of pond ash are the lack of willingness and change in mindset of both the producers and the users. The producers do not take any initiative in solving the hurdles for efficient transportation and loading logistics. The users are locked in the battle of defining the material as waste generated by other people. Improved process
Towards its effort of providing a clean and healthy working environment, Development Alternatives has replaced this manual mixing process by a mechanized one. It not only improves the mixing quality of the two components but also produces a superior quality of fired product. This type of mixing process also takes care of the working conditions of the moulders and even increases their output by providing a congenial atmosphere. Practical demonstrations at entrepreneur’s site have also demonstrated that this mechanized mixing process improves profitability for the entrepreneurs in the form of uniform quality, reduced breakage and higher productivity per person. Thus introduction of a cost effective mechanization is slated to be a win-win situation for all. Policy Issues The fixation of fly ash quantity of 25% by weight is one of the hurdles for its wide acceptance. Fly ash is a non plastic material by nature. Addition of it reduces the plasticity of the soil. Typically soils in India are varied in nature. In the Indo Gangetic plains of North and Eastern India, soils with higher clay content and plastic in nature are available. Some reported plastic soils are also found in Kerala and the coastal belt of Southern India. The rest of India comprising the whole of Central and Western part and Orissa, Chattisgarh and Jharkhand contains non plastic silty to sandy soils. High concentrations of non plastic materials will reduce the plasticity of the soils and result in very high breakage. In some cases even the workability of the soils will be reduced. Thus the legislation of 25% addition by weight of fly ash is a questionable proposition judging from the varied quality of clay. Even in clayey soils the fly ash addition can exceed the specified limits without any deterioration in the fired quality.
One of the burning
issues at the moment is transportation of fly ash from within 100 km
radius and the associated cost implications which will result in
increased production cost of the fired bricks. The legislation of
Government of India has put the entire cost of fly ash transportation on
the users. The brick entrepreneurs have to arrange and pay for their
transportation. If this increased cost is shared between the both the
stakeholders then it will create a congenial atmosphere for its use.
Marginal increase of production costs can be absorbed by the producers.
The cost of transportation of fly ash by thermal power plants can be
absorbed within their power tariffs which will not pinch the consumers.
Thus if both the parties are willing to create space for additional cost
absorption, then utilization of this waste material will not affect our
future generation and will set a precedence of user-producer joining
hands in improving the environment of our country.
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shelter for all, this demand is slated to increase exponentially in the
future years. If 30% of the total brick production is substituted by fly
ash to the tune of 20% - 30% by weight of each brick then only burnt
clay brick production can take care of the total amount of fly ash
produced in India, which is remarkable.
Commonly
in India, green bricks are moulded manually. The soil is dug by hand and
mixed with water to produce the green bricks. Since fly ash is a lower
density material than the soil being used, manual mixing of it is
practically impossible. There are reported instances of fly being mixed
manually in the states of Maharashtra, Madhya Pradesh but quality of the
fired bricks is not being consistent. High concentrations of unmixed fly
ash present in the bricks adversely affect the strength of the bricks.