*Designs, P.W.D., Madras-5.
**Concrete and Soil Engineering Research Laboratory, Madras-5.
The Nation’s programme of vast industrialisation and construction of multi-purpose and other projects under the Plans has resulted in shortage of cement. The suitability of fly-ash as a puzzolana and as a part replacement to cement is therefore a welcome piece of information. Results of a detailed study conducted in the Madras Laboratories on Basin Bridge fly-ash and the preliminary study under way with the Neyveli fly-ash are given in the paper.
The results of the tests conducted with Basin Bridge fly-ash indicate it as a good puzzolana which can be safely used as part replacement or addition to cement for construction works, up to 15 per cent. The preliminary tests with Neyveli fly-ash have also yielded some encouraging results. The CaO content (25.3 per cent), however, is much higher as compared to fly-ash from Basin Bridge (1.67 per cent). The effect of high CaO content on the strength, etc., remains to be studied. It is felt that fly-ash of low sulphur content (below 3 per cent) can be used in reinforced concrete jobs after due testing without any harm to reinforcement. With regard to presence of free carbon content it has been contended that coal-ash which has 12 per cent free combustible carbon (as against permissible 10 per cent) can be used only after further investigations about strength and durability and may not be generally suitable for construction works.
In the light of the present studies and the results of studies conducted abroad, the authors advocate the use of fly-ash, wherever it is economically available, particularly in view of the laboratory studies undertaken all over the country to test its different properties and assessing its suitability.
