Improved Specifications for Hydraulic Cement Concrete
Improved Specifications for Hydraulic Cement Concrete

Author: Woodrow J. Halstead

Publisher:

Published: 1983

Total Pages: 128

ISBN-13:

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This is the final report of a study of the application of statistical concepts to specifications for hydraulic cement concrete as used in highway facilities. It reviews the general problems associated with the application of statistical techniques to hydraulic cement concrete, and discusses the potential advantages and disadvantages to applying such techniques to concrete used in the construction of transportation facilities. During the course of the research reported here, it was found that for the Virginia Department of Highways and Transportation, contracts for concrete structures generally involved small volumes of concrete, and that the usual frequency of sampling and testing did not provide sufficient test results for establishing specifications based on usually recommended risks to both the contractor and the state. Increases in the frequency of testing to provide the recommended risks would result in excessive increases in costs. Accordingly, procedures for acceptance of concrete on the basis of small-to-medium sample sizes at increased statistical risks, but based on sound engineering judgment, were developed and are included in the report. Also included are complete recommendations for a revised specification for hydraulic cement concrete and a discussion of the statistical significance of the recommended changes. Recommended revisions to the Virginia Test Manual and the Instructions to concrete inspectors that would be needed should the revised specification be accepted are included in the appendices. Also included as an appendix is a resume of practices and requirements in other states using statistical concepts in their specifications for hydraulic cement concrete.

Pilot Study of Proposed Revisions to Specifications for Hydraulic Cement Concrete
Pilot Study of Proposed Revisions to Specifications for Hydraulic Cement Concrete

Author: Woodrow J. Halstead

Publisher:

Published: 1985

Total Pages: 74

ISBN-13:

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This report summarizes the results of a pilot study of the statistical acceptance procedures proposed for adoption by the Virginia Department of Highways and Transportation. The proposed procedures were recommended in the report titled "Improved Specifications for Hydraulic Cement Concrete" and issued in 1983. This study revealed that practical difficulties would likely be encountered if the initially proposed revisions were adopted. Major problems were noted with the proposed system of random sampling based on a predetermined truckload of material, the definition of the total concrete placed on the contract as a single lot, the initially proposed requirement for average entrained air content, and the present practice of accepting concrete on the basis of its having 85% of the required 28-day strength at 14 days. After study of the findings, a revised proposal has been made for introducing such concepts into the Department's specifications for hydraulic cement concrete. The proposal is that a day's production of hydraulic cement concrete be considered a lot and that three samples per lot normally be taken for judging acceptability. The proper parameters for judging acceptance are based on a computerized statistical program (non-central-t) developed by the New Jersey Department of Transportation. These are discussed in the report and are recommended for adoption by the Virginia Department of Highways and Transportation. Where conditions warrant, a larger number of samples per day may be required with consequent reductions in the risks of accepting poor concrete.

Improving Concrete Quality
Improving Concrete Quality

Author: Karthikeyan H Obla

Publisher: CRC Press

Published: 2014-06-25

Total Pages: 218

ISBN-13: 1466592125

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Improve the Quality of Concrete, Improve the Quality of Construction Quality measurement is not prevalent in the concrete industry and quality investment is not seen as potentially generating a positive return. Improving Concrete Quality examines how and why concrete quality should be measured, and includes instruction on developing specifications with the aim of improving concrete quality. Reduce Concrete Variability: Reduce Costs and Increase Volume The first part of the book considers the tangible and intangible benefits of improved quality. The later chapters explore concrete strength variability in detail. It provides a greater grasp of the variation in concrete, as well as a deeper understanding of how material variability affects concrete performance. The author discusses the components of variability (material, manufacturing, testing) and provides steps to measuring and reducing variability to improve the quality of concrete. The text also contains a chapter on data analysis for quality monitoring and test results. Come Away with Practices and Tools That Can Be Applied Immediately: Provides techniques and how specifications can improve concrete quality Offers a clear understanding of the link between the materials (cement, SCM, aggregate, water, air), manufacturing, testing variability, and concrete quality Includes information on analyzing test data to improve quality Improving Concrete Quality quantifies the benefits of improved quality, and introduces novel ways of measuring concrete quality. This text is an ideal resource for quality personnel in the concrete industry. It also benefits architects, engineers, contractors, and researchers.