Use Of 1200 Mm Diameter Round Panels For Quality Control Testing Of Sfrc Used In Pre-Cast Tunnel Lining Segments
An earlier paper  examined the variability of test results obtained for beam tests performed on steel-fibre reinforced concrete used in the manufacture of precast segmental tunnel lining units as part of a commercial supply contract. It confirmed the existence of a commercially unacceptably high coefficient of variation (COV) in the order of 28% for results obtained by the ASTM C1609/C1609M beam test method . This paper continues the investigation of high variability of test results for SFRC beams tested to ASTM C1609/C1609M method and presents an arguably superior alternative test for determining residual flexural strength using 1200mm diameter panels that provides substantially reduced variability. A robust analysis of the results obtained from numerous tests on sets of panels and beams has demonstrated a correlation between the two test methods within a 2.5% error margin. This margin can be considered negligible as well as conservative. It can therefore be accepted that a design residual strength at 3mm determined using ASTM C1609/C1609M beams is equivalent to an identical design residual strength at 10 mm determined using the 1200mm diameter panels tested in a manner similar to ASTM C1550. Based on this correlation, the equivalent minimum characteristic residual strength obtained using the panel tests has been determined and this equivalent minimum characteristic value can be satisfactorily used for acceptance criteria during production quality control testing.
Keywords- Testing, panel, correlation, residual flexural strength, steel fibre reinforced concrete, variability.