STP205

    A Physical Method for Determining The Composition of Hardened Concrete

    Published: Jan 1958


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    Abstract

    Determination of the proportions of materials in hardened concrete in structures becomes desirable when question arises as to the quality of the concrete actually placed. Existing methods of chemical analysis depend heavily on knowledge of the chemical composition of the aggregates, which is seldom available.

    This paper describes a “point-count” method of determining the cement content of hardened portland-cement concrete by analysis of a cut section with a traveling microscope. The voids and aggregate content are estimated by direct observation; the cement content is then determined by difference, with correction for non-evaporable water in the cement paste. Sand-aggregate ratio is also computed.

    Results of microscope analysis of various laboratory-mixed concretes are compared with original mix proportions. Comparisons are also made with results of chemical analysis according to ASTM Method C 85-54 and two other chemical methods developed during the investigation.

    The precision of each method is estimated, and the advantages and limitations are discussed. It is concluded that the microscope analysis is at least as precise as the chemical methods, and that it requires less time and equipment. With further study and refinement, it offers promise of providing a reliable estimate of the cement content of hardened concrete within the precision of construction and sampling.


    Author Information:

    Polivka, M
    Assistant Professor of Civil Engineering, Professor of Civil Engineering, and Graduate Student in Engineering Science, University of California, Berkeley, Calif.

    Kelly, JW
    Assistant Professor of Civil Engineering, Professor of Civil Engineering, and Graduate Student in Engineering Science, University of California, Berkeley, Calif.

    Best, CH
    Assistant Professor of Civil Engineering, Professor of Civil Engineering, and Graduate Student in Engineering Science, University of California, Berkeley, Calif.


    Paper ID: STP39465S

    Committee/Subcommittee: C09.61

    DOI: 10.1520/STP39465S


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