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Home > Publications > International Concrete Abstracts Portal
The International Concrete Abstracts Portal is an ACI led collaboration with leading technical organizations from within the international concrete industry and offers the most comprehensive collection of published concrete abstracts.
Showing 1-5 of 18 Abstracts search results
Document:
SP223-12
Date:
October 1, 2004
Author(s):
Katharine Mather
Publication:
Symposium Papers
Volume:
223
Abstract:
The applications of light microscopy in concrete research are outgrowths of its applications in petrology, mineralogy, and chemistry, but there is more quantitative emphasis in its use in concrete research than is common in petrology. Metallographic and combined petrographic and metallographic techniques are used to study portland cement. Normal petrographic methods are used to study aggregates and cement-aggregate reactions. Air content and bubble spacing in concrete are investigated by linear traverse and point-count techniques. The use of light microscopy in making comparative studies of the microstructure of concrete is described.
DOI:
10.14359/13504
SP223-11
Katharine Mather and Bryant Mather
A detailed description of the method for petrographic examination of aggregates for concrete as it has been developed for use by the Concrete Laboratories of the Corps of Engineers is presented. The differences in procedure which depend upon the nature of the sample submitted and the purposes of the examination are described. Suggestions are made concerning the features to be delineated, the amount of material to be examined, and the organization and presentation of the results of the examination. It is hoped that the information presented will serve to clarify the concept of what is meant by petrographic examination of aggregates and, perhaps, ultimately, contribute to greater uniformity in the making of such examinations.
10.14359/13503
SP223-06
Bryant Mather
Crystals are found in some entrained-air voids of all concrete that has been "left out in the rain" or stored while damp. These crystals can be observed through petrographic examination of thin or ground concrete sections at normal magnification. If the concrete was made using a cement with a high tricalcium aluminate (C3A) content (over 8%), it is likely that areas in it will be covered with ettringite crystals - secondary ettringite.
10.14359/13498
SP223-13
This lecture is about concrete - specifically, hydraulic-cement concrete. If one starts with the dry powder that is hydraulic cement - usually the particular class of hydraulic cement known as portland cement - and adds water, what results, depending on the amount of water added, is cement paste or grout. Grout can be poured like gravy. If fine aggregate is added, the result is mortar or sanded grout. If both fine aggregate and coarse aggregate are added, the result is concrete. As the Supreme Court of Pennsylvania once wrote in a decision dealing with cement-manufacturing plants, "cement is to concrete as flour is to fruitcake." My first point is, to get proper concrete, get the terminology right. There is no such thing as a cement mixer. And sand is not a synonym for fine aggregate; sand is a class of fine aggregate produced by nature rather than by rock crushers and grinding mills.
10.14359/13505
SP223-15
For two centuries the U. S. Army Corps of Engineers (CE) has been developing high-performance concretes. In the 1840s, various Corps of Engineers’ officers, including Robert E. Lee, developed concretes that could be placed underwater for construction of coastal defense facilities. General Q.A. Gillmore, whose device for measuring time of setting of cement paste is still used, published a book in 1863 on hydraulic cement and mortar. In 1871, he published a book on concrete, which introduced concrete technology from France that was significantly higher-performance than that then used in the United States. Contemporary development of high-performance concrete began in 1935 at the CE Concrete Laboratory at Eastport, Maine, in support of the Passamaquoddy Tidal Power project. The objective was to develop concrete able to resist twice daily immersion in sea water and freezing in the winter when the tide went out. That objective was achieved. In 1970, when confronted with the problem of severe abrasion-erosion damage in stilling basins below dams, a solution was found in the development of concretes having strengths greater than 100 MPa. This was done using silica fume and high-range water-reducing admixtures. Similar and higher-strength high-performance concretes have also been developed for defense purposes as part of the protective-structures portion of the U.S. military research and development (R&D) program. When stronger concrete or concrete that must resist a more severe exposure is needed, the Corps of Engineers’ concrete R&D capability has been able to develop it, and I expect it will continue to be able to do so.
10.14359/13507
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