Abstract
The ASTM C1550 round panel test is now used widely to assess the post-crack performance of fiber-reinforced concrete (FRC) and fiber-reinforced shotcrete (FRS) and is firmly established as the most repeatable means of post-crack performance assessment available for these materials. However, the 75-mm standard specimen thickness for this test method has limited its application to relatively thin-walled structures such as FRS linings in mines and tunnels. The performance characteristics of FRC in bending depend on the thickness of a member, and thus a specimen with a thickness close to that in the intended application should be used for representative performance assessment. For this reason, tests such as ASTM C1609/C1609M, based on a 150-mm-deep beam, are typically used for thick-walled applications such as FRC tunnel linings and pre-cast elements. Unfortunately, the high single-operator variability characteristic of performance parameters obtained using beam tests has burdened the construction industry with unnecessarily expensive FRC designs, because the resulting margin between target performance and design requirements becomes excessively large. In response to this, demand has arisen for an enlarged version of the 75-mm-thick ASTM C1550 panel that can be used as a quality assurance tool for thick-walled FRC applications. The present paper describes the development of a version of the ASTM C1550 round panel 150 mm thick and 1200 mm in diameter with specific emphasis on developing thickness correction factors and characterizing the single-operator variability for these large test specimens. It also establishes a correlation between residual strengths measured using ASTM C1609/C1609M beams and using 1200-mm-diameter round panels at comparable crack widths.
