Error Propagation in the ASTM C1609/C1609M Beam Test for Fiber-Reinforced Concrete

ABSTRACT

The post-crack flexural performance of fiber-reinforced concrete (FRC) is commonly assessed using simple beam specimens such as the ASTM C1609/C1609M, Standard Test Method for Flexural Toughness of Fiber-Reinforced Concrete (Using Beam with Third-Point Loading), third-point-loaded beam test. Like most beam-based test methods for FRC, the performance revealed by this test method exhibits high variability. An investigation based on variance–covariance analysis has been undertaken to examine the sources of variability in this test method and identify the true variability in FRC once extraneous test-related sources of variability have been isolated. This analysis has determined that friction in the supporting rollers and the location of the crack relative to the center of the beam are the main test-related sources of variability in FRC performance assessment using the ASTM C1609/C1609M test method. Given that the apparent magnitude of flexural strength also increases with friction, it is advisable to place limits on the maximum acceptable magnitude and variance in roller friction during a beam test so that the apparent variability in the output can be moderated. Control of the location of the crack in a third-point-loaded beam is more difficult and may not be desirable when seeking a representative estimate of mean flexural performance.