The American Concrete Institute (ACI) sub-committee 236A, Workability of Fresh Concrete, upon its creation in fall 1999, immediately faced the task of determining appropriate methods to measure concrete workability. Using a material science-based approach, workability should be defined using rheological methods. The instrument most used for determining rheological parameters is a rheometer. There are several concrete rheometers used around the world that have significant design differences, but no standard method with which to compare their results. ACI 236A members determined that, as no reference material was available, one method to compare the rheometers would be to test them under the same conditions using the same concrete mixtures. A tentative analysis comparing two rheometers was performed but did not involve most of the available rheometer designs. A first set of round-robin testing was organized in 2000, allowing the direct comparison of five types of rheometers. This first comparison test was sponsored by the Concrete Research Council (CRC) of ACI and by industry. It was held at the Laboratoire Central des Ponts et Chauss es (LCPC) facility in Nantes, France, on October 23-27, 2000. The rheometers selected included commercially available concrete rheometers (four), and one coaxial concrete rheometer developed for research. After the test and subsequent report it was apparent that some issues were still unresolved; therefore ACI 236A committee requested an extension grant from CRC and more industrial support to conduct a second set of round-robin testing. The second test was performed on May 19-23, 2003, in the laboratory of Masters Builders, a Degussa Construction Chemical company, in Cleveland OH, (USA). The authors of this report are principal investigators who participated in this second test and contributed to the report. This report describes the tests performed and the results obtained. Following the same procedure as in the first comparison test, this report was not published as an ACI document and therefore was not submitted to the Technical Activities Committee (TAC) for approval. There are two reasons that this is not an ACI document: 1) ACI documents are guidelines and practice recommendations, not research reports; 2) all ACI reports are consensus documents balloted and approved by the members of a committee, while this report only reflects the views and opinions of the authors. All members of ACI 236A were invited to review the document prior to publication (as shown in the acknowledgements). It was also discussed during the regular meetings of ACI 236A during Fall 2003 and Spring 2004.
Citation: NIST Interagency/Internal Report (NISTIR) -
NIST Pub Series: NIST Interagency/Internal Report (NISTIR)
Pub Type: NIST Pubs
concrete, rheology, rheometer