ASTM WK72347

    Revision of C39 / C39M - 20 Standard Test Method for Compressive Strength of Cylindrical Concrete Specimens

    (What is a Work Item?)

    Active Standard: C39 / C39M - 20

    Developed by Subcommittee: C09.61 | Committee C09 | Contact Staff Manager



    WK72347


    Keywords

    concrete core; concrete cylinder; concrete specimen; concrete strength; compressive strength; core; cylinder; drilled core; strength;;

    Rationale

    ASTM C 39 is the only concrete strength testing procedure under C09.61 that does not currently have a required reporting item related to curing conditions, history, or adherence to the standard used for obtaining the specimens. This omission has been called into question by multiple users of the standard, inspectors, and officials asking for clarity from the subcommittee why C39 does not include this provision. ASTM C39 should be updated to both provide reviewers of strength reports a complete summary of the recorded measures and steps taken to develop those documents and match other strength and compression reporting standards established under C09.61. Other C09.61 reporting requirements for example: ASTM C78 10.1.7 Curing history and apparent moisture condition of the specimens at the time of test, ASTM C293 9.1.7 Record of curing and apparent moisture condition of the specimens at the time of test, ASTM C469 8.1.3 Curing and environmental histories of the specimen, ASTM C496 9.1.7 Curing history, ASTM C512 10.1.4 Storage conditions prior to and subsequent to loading, ASTM C873 9.1.9 Curing method used, 9.1.11 Maximum and minimum temperature information obtained at job site to define curing conditions of specimens in place, 9.1.13 Other information pertaining to job conditions that could affect the results. In previous ballot versions, most recently in 2016, information was presented regarding ACI Building Code 318 Section 26.12.3.1a, ACI 301-16 Section 1.6.3.2e, and ACI 311.6-09 Section 2.5.1 require that acceptance cylinders to be cast and standard cured in accordance with Test Method C31. Test Method C31 requires reporting the following information to the laboratory that will test the specimens: 12.1.4 Slump, or slump flow, air content, and concrete temperature. 12.1.5 Curing method. For standard curing method, report the initial curing method with maximum and minimum temperatures and final curing method... Contractors, specifiers, and, concrete producers receive only the C39 report, not the C31 report. The C39 report does not report the maximum and minimum temperatures during initial curing; so there is no way to ensure Code compliance in the area of satisfactory initial curing from the reported strength performance. An ongoing program conducted by the Colorado Ready Mixed Concrete Association showed that initial curing is not in accordance with ASTM C31 in about half of the projects. Requiring the reporting of maximum and minimum temperatures during initial curing in the C39 report will ensure that proper initial curing practices are adopted in the field in compliance with Code provisions. Initial curing that is not in accordance with ASTM C31 can result in up to 30% reduction in compressive strength (Kane et al. 2015; Obla et al. 2005; New Mexico study 1995; Meininger 1983; Bloem 1954). Inconsistent initial curing will also result in higher variation in compressive strengths. Concrete producers compensate for both effects by targeting a higher compressive strength. Proper reporting of the recorded initial curing at the job site can offer the following benefits: 1.Concrete mixtures can be designed to target lower strengths which will help lower cementitious contents and paste volumes. This in turn can improve performance through better resistance to Alkali silica reaction and reduced cracking due to temperature and shrinkage. Mixtures will also be more sustainable with a lower carbon footprint and cost effective. 2.There will be reduced occurrences of low strength investigations. This can reduce time and costs in the project and foster a partnering environment. Better performance, improved sustainability, reduced time and costs will increase confidence in concrete construction and thus benefit all stakeholders. Slump (C143), air content (231), and temperature (C1064) standards require the reporting of the test results. Requiring the reporting of initial curing as part of the C39 report will make this consistent with the other fresh concrete tests. It will also make it consistent with ACI 311.6-09 Section 3.3.12 reporting section which states that the maximum and minimum temperatures during initial curing shall be reported. ACI 311.6 is the specification for testing ready mixed concrete. A previous ballot required the reporting of both the maximum and minimum temperature and the curing method during the initial curing. That ballot received several negatives from test labs. Some of the negatives pointed out the difficulty in reporting curing method as it was subjective and may require extensive description. The curing method is required to be reported to the laboratory in C31 12.1.5 or the moisture condition history is required in C42 7.10.6; so that information is already available in some form prior to the scope of work for C39.

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    Work Item Status

    Date Initiated:
    03-20-2020

    Technical Contact:
    Lee Thrasher

    Status:
    Draft Under Development