Please use this identifier to cite or link to this item: http://localhost:8081/xmlui/handle/123456789/3711
Title: SELECTION AND SPECIFICATION OF AGGREGATES FOR BIG DAMS
Authors: Mukund, K. R.
Keywords: WATER RESOURCES DEVELOPMENT AND MANAGEMENT;AGGREGATES BIG DAMS;AGGREGATES MASS CONCRETE;MASS CONCRETE
Issue Date: 1972
Abstract: A systematic study of the properties and characteristics of aggregates will enable production of suitable concrete, which besides conforming to. the design and specification requirements of strength and durability, will also equally ensure economy, especially in mass concrete for big dams. These aspects of selection of aggregates for mass concrete have been reviewed and discussed in this study. Specifically, the properties of aggregates and their effects on the proper-ties of mass concrete, Geological and related characteristics of aggregates and aggregate deposits, specifications and tests for quality of aggregate, selection of aggregates, aggregate processing and safeguarding of quality during processing, and finally the several controlling measures adopted for a proper selection of aggregates on some important projects in India have been covered in the eight chapters of the dissertation. The important properties of aggregates studied have been grouped into (a) physical properties (b) chemical properties; and (c) gradation characteristics, and the effect of these properties on the properties of concrete has been discussed. Topography and geology often limit the choice of aggregates to a particular source. The aggregate sources should be thoroughly investigated to ensure that. only such rocks or such natural gravel and sand, as are of the desirable shape and size, geologically sound, hard and durable, free from deleterious coatings and not contaminated by reactive minerals are selected for mass concrete. In this direction, several geological characteristics of rocks which are suitable as aggregates have been dealt with. The several provisions made in the specifications, which have been standardized by the Indian Standards Institute, for aggregates used in mass concrete have been examined with particular reference to quality and gradation. The tests on aggregates which have been designated by the ISI, ASTM, USBR, U.S. Army Corps of Engineers, and the British Standards Institute have also been briefly described, indicating the significance of such tests to ensure adherence to standard specifications, and structural as well as environmental requirement s. Selection of suitable aggregates is a very significant factor in concrete mix design for mass concrete works. This requires a critical appraisal of the important characteristics of aggregates which have been studied critically and presented in the dissertation. Aggregate gradation studies have been dealth with in detail, since a properly graded aggregate exerts vast controlling influence on the workability and economy of concrete, besides resulting in lesser cement and water consumption. The desirability of selecting natural aggregates has been high lighted. Certain practical aspects in processing and handling of aggregate, which cause increase of undersizes and thereby alter the gradation of aggregates have been dis.. cussed. Remedial measures normally adopted in avoiding such breakages of aggregate causing disruption of the gradings have been discussed. Regarding processing and handling of fine aggregate, it is desirable to correct the gradings to conform to the specified limits by suitable processing. As a follow up action, a brief survey of the several controlling measures, by way of a systematic and scientific investigation for aggregate sources, selection of aggregates, processing and handling, laboratory tests etc. as were adopted for the mass concrete of Bhakra and Rihand dams has been made. It may be noted that in both these projects, aggregates have been selected on the basis of detailed laboratory and field tests on several aggregate properties and also continuous gradings for coarse aggregates upto a maximum size of 7" for Bhakra and 6" for Rihand have been adopted. One important difference between the two projects. is that for the Bhakra Dam mass concrete, natural gravel and sand have been used, while crushed coarse and fine aggregates have been used for the Rihand Dam. In both the projects, aggregate processing and handling were highly mechanized. In general, it has been concluded that it is always desirable to ensure that aggregates used for mass concrete conform to spefications, in spite of additional expenditure in aggregate processing and handling. This expenditure is more than compensated by way of reduced cement and water requirements for concrete, improve, workability, reduced heat of hydration and drying shrinkage characteristic of concrete.
URI: http://hdl.handle.net/123456789/3711
Other Identifiers: M.Tech
Research Supervisor/ Guide: Verma, Mahesh
Aminbhavi, L. T.
metadata.dc.type: M.Tech Dessertation
Appears in Collections:MASTERS' THESES (WRDM)

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