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Suggested Citation:"Introduction ." National Academies of Sciences, Engineering, and Medicine. 2011. Rheological Characterization of Flow Table Reference Material. Washington, DC: The National Academies Press. doi: 10.17226/22870.
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Research Results Digest 360 August 2011 INTRODUCTION The flow table is described in AASHTO Standard Specification M 152, “Flow Table for Use in Tests of Hydraulic Cement,” as an apparatus “. . . used in making flow tests for consistency of mortars in tests of hy- draulic cement.” In brief, a mortar’s flow value, which is an indication of its work- ability, is measured by unmolding a sample of the mortar on the flow table, dropping the table a specified number of times, and mea- suring the increase in diameter of the sam- ple, expressed as a percent of its original diameter. Use of the flow table is referenced in AASHTO T 71, “Effect of Organic Im- purities in Fine Aggregate on Strength of Mortar”; T 106, “Compressive Strength of Hydraulic Cement Mortar Using 50-mm or 2-in. Cube Specimens”; and T 137, “Air Content of Hydraulic Cement Mortar.” Footnote 3 of the 2003 revision of AASHTO M 152 states that a reference material for calibration of a flow table is available from the Cement and Concrete Reference Laboratory (CCRL) at the Na- tional Institute of Standards and Technol- ogy, Washington, DC 20234. This refer- ence material is compounded in batches by CCRL from a white mineral oil and a finely ground silica powder. The oil viscosity is not measured, but the value reported by its manufacturer is recorded. The powder fine- ness is obtained by a permeability method similar to the Blaine method (e.g., ASTM C204, “Fineness of Hydraulic Cement by Air-Permeability Apparatus”), although in recent years the particle size distribution of the powder has also been measured using a laser diffraction particle size analyzer. Each batch of silica powder is ground at CCRL from an Ottawa sand meeting the require- ments of ASTM C778, “Standard Sand,” until its measured fineness matches that of the previous batch. The powder is then mixed with the oil and the flow value of the batch is determined using the flow table at CCRL. This flow table is identical to com- mercially available units. Thus, flow val- ues obtained with the CCRL flow table are considered reference values for use in the calibration of all other flow tables in the United States. Although the CCRL flow table is well maintained and has been successfully used for preparation of all flow table reference RHEOLOGICAL CHARACTERIZATION OF FLOW TABLE REFERENCE MATERIAL This digest summarizes key findings of NCHRP Project 20-07/Task 272, “Rheological Characterization of Flow Table Reference Material,” conducted by the AASHTO Materials Reference Laboratory under the direction of the principal investigator, Haleh Azari. The digest is based on the project final report authored by Haleh Azari and Chiara Ferraris of the National Insti- tute of Standards and Technology. The full text of the project final report is available for download at http://apps.trb.org/cmsfeed/TRBNetProject Display.asp?ProjectID=2600. Responsible Senior Program Officer: E.T. Harrigan NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM

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TRB’s National Cooperative Highway Research Program (NCHRP) 360: Rheological Characterization of Flow Table Reference Material summarizes the key findings of a project that characterized available batches of cement and concrete reference laboratory (CCRL) flow table reference material. The project also explored more efficient, stable, and reproducible methods for future production of the reference material that is independent of the CCRL flow table.

The contractor’s final report, which is summarized by NCHRP RRD 360, is available online.

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