With rapid industrialisation, increasing quantities of pollutants are being spewed into the atmosphere and water sources in solid, liquid and gaseous form. These pose a major health hazard in most urban and semi-urban areas. There is an urgent need to find a solution to this problem.

Amount preventive measures adopted by industries, one under examination involves ways in which the wastes, specially those in the solid form, can be used as ingredients in building materials. This is all the more important considering that these are in short supply. Here we examine some of the wastes and their potential use in construction. The various applications possible with these wastes have also been summarised in the table below.

Flyash is a powderous bye-product of coal incineration in thermal power plants. As the country has a large number of such plants huge quantities of flyash are produced in tandem with the generation of electricity. This is uniformly graded compound of silica, alumina and unburnt carbon. The flyash exhibits pozzolonic (brick dust/surkhi is a pozzolonic material) qualities, a property which enables it to form strong mortars in combination with other materials like lime. It has also been successfully used as a part substitute for cement in cement sand mortars, enabling substantial savings in cost. Other applications of flyash include its use as additives in pozzolonic cements, in flyash sintered (burning at high temperature) bricks and in flyash concrete blocks.

Various institutions like the Central Building and Research Institute, Roorkee have done pioneering research in finding means to utilise flyash. Some of them have been enumerated to emphasise the ease with which these can easily be adapted into normal construction practice.

Potential uses of Wastes as Building Materials

Industrial waste	Application
Blast furnace slag	In Portland slag cement, super sulphated and metallurgical cements: cements with special properties, oil well, expanding masonry in refractory and in ceramics; aggregate in concrete as a metallurgical slag structural fill
Ferroalloys and other metallurgical slags	As additives for pozzolona metallurgical cement, structural fill.
Bye-product gypsum	As gypsum plaster, plaster boards, slotted tiles; as set controller in manufacture of expansive and other special cements; cement pozzolana-gypsum walling blocks and sheets as mineralizer.
Lime sludge (phospo-chalk, paper and sugar sludge, carbide sludge)	In building lime, as raw material for cement manufacture, manufacture of masonry cement.
Redmud	As a corrective material. In making construction blocks, as cellular concrete additive, in the making of heavy products and red mud bricks; in aggregate making wall and floor tiles.
	(From Building materials: Perceptions and Projects by S.K. Chopra)

Cement concrete consists of cement, stone aggregates and sand mixed at optimum moisture levels. The substitution of flyash in this mixture catalyses the cement reaction and adds to the ultimate strength of the cement. The addition of lime further enhances the strength. This can be readily mixed on site to produce flyash concrete.

The concrete prepared by the above procedure may be used to manufacture solid or hollow concrete blocks much in the same way as the normal concrete blocks are made. A major saving can be effected by 25-30 percent flyash substitution, without hampering the performance characteristics of the concrete block i.e. the masonry unit.

Flyash substitution in mortars for brick masonry walls of the order of 1:3:6 or 1:4:8, cement: flyash: sand in place of the conventionally used 1:6 or 1:4 respectively can cut costs without compromising on properties. Upto 15 percent saving may be affected by the use of the 1:3:6 mortar in place of the conventional cement-sand-mortar of the order of 1:6.

A lot of wastage on site is due to the rapid hardening of cement resulting on the one hand, in wastage of materials; on the other hand, time is wasted when small quantities are mixed. Flyash is found to retard the setting time of cement making it possible to use the mixed mortar for longer durations.

Development Alternatives has experimented with using flyash as a stabiliser in the manufacture of compressed earth block. These blocks are obtained by a process of manual compaction of means of mechanical presses like the Balram, Astram, Auram etc. It has been observed at the laboratories of Development Alternatives that flyash reaction is accelerated with the addition of lime. However, the flyash component is limited to about 20 percent in volume. Moreover clayey or silty soil if found to obtain better reaction which binds stronger with the flyash and improves water resistance. A block with 20 percent flyash and 5 percent lime has been found to achieve 35-40 kg/sq cm strength and can easily replace cement (used as a stabilizer), provided the soil is suitable.

Pressmud is another industrial waste produced in huge quantities by sugar factories. Sugar is clarified using either the sulphatation or the carbonation processes. The pressmud form the sulphatation process is being actively used in the manufacture of fertilizer. Pressmud from the carbonation process contains carbonates of aluminium, iron and magnesium and cannot be used as fertiliser.

Pressmud is locally burnt by making heaps and the result is a low-grade lime which besides being used as whitewash by the Public Works Department for pavements, is used as an adulterant in lime. Development Alternatives has conducted feasibility studies to utilise this material as a compacted block. Various additives like coarse sand and clay were added restricting stabilisation only to physical levels which basically means to engineer the blocks only by altering the grading of the components. No chemical reaction of the components is initiated.

Though improvements in strength, water resistance etc were achieved, these blocks were found to be poor in impact resistance. Research is still in progress to overcome these problems. A test wall has also been constructed to evaluate the mortar combinations and to subject the blocks to aging tests.

With the fast depleting resource base it is quite obvious that construction technologies should be linked to the effective utilisation of industrial wastes, thereby achieving two objectives with the same effort, prevention of pollution through waste utilisation and the production of building materials. q

Manibeli Satyagraha

A dharna is being staged since June 7 by NGOs and citizens at Shramshakti Bhawan on Rafi Marg, New Delhi to protest against the government’s decision not to stop the construction of the Sardar Sarovar Dam.

“We will continue the dharna as long as Medha is on a fast”, says Ratna Mathur of Alternative Communications Forum who along with K.P. Sasi made the documentary film on Narmada entitled “The Valley Refuses to Die”.

The protesters are demanding a “comprehensive review” of the project. So far the government agencies, the World Bank and other bodies have studied one or the other aspect. But such a sectoral approach does not go to the heart of the problem; hence the piecemeal solutions suggested have understandably not had the desired impact. Stepping up the re-habilitation of the oustees, for example, will not address the main issues regarding sustainable development raised by such mega-projects.

In fact, the concerned state governments can ask for a comprehensive review by the Centre under the constitution of the Narmada Water Disputes Tribunal. An independent team approved by the government and Narmada Bachao Andolan (NBA), can undertake the review once the green signal is given by the government.

In the meanwhile, conflicting reports have been appearing: one stated that the NBA will not do samparpan now that the police have withdrawn from Manibeli and evictions halted. Whether the police will be kept at bay by the state government remains to be seen. But if past record is anything to go by, the authorities will not keep their word. In fact, says Ms. Mathur each party in the state in Madhya Pradesh, whether Congress or BJP, agreed with the NBA during meetings to ask for a comprehensive review, but never did so when in power.

Inspite of overwhelming evidence - the Morse Committee report, the World Bank’s withdrawal of financial support - the government has remained adamant and gone ahead with the construction of the dam. As a consequence, hundreds of families are facing the threat of submergence in the coming monsoon; many of these families haven’t been given land, or even shown it.

But the people have resolved that they would rather drown than leave their homes and villages. They firmly believe that the dam (and the submergence) is illegal and unjust and have decided to oppose it.

Since the last two years, when the government has been claiming that there was a possibility of submergence, the people of the valley had clearly indicated that they would not leave their homes by staging a satyagraha at Manibeli, the first of the villages that will be submerged. The people had formed their Samarpit Dals - the “Save or Drown” squads: these had pledged that, if any submergence took place, they would go under with the huts. Last year the government stopped the construction at 33 m and thanks to deficient rainfall the submergence did not occur.

This year, however, is different study. The government is planning to raise the height of the dam to 61 metres by the time monsoon starts. The lowest huts are at 51 to 55 metres. There are about 350 families that face submergence.

This year too, the people of the valley and the activists have formed the Samarpit Dal. If there is any submergence then there will be samarpan. But whether the samarpan will lead to justice being done will depend critically upon how the nation responds, how all of us respond. The Samarpit Dal is staging a dharna along with its supporters from the valley and outside in solidarity. The NBA has appealed to all the organisations working on social, developmental, environmental, human rights issues, as well as concerned individuals to come forward to support and strengthen the satyagraha. The struggle against the destructive development symbolised by the Sardar Sarovar project has entered a critical even decisive phase. It is your participation (or otherwise) that will help decide what finally happens.

Narmada Bachao Andolan
C/o Parivartan Nimbalkar Chamber
Nandia Bazar, Baroda - 390 001

Tel: 0265-554979

Fax: C/o 0265-45163