Abstract

Panel and beam tests are widely used to assess the flexural performance of fiber-reinforced concrete (FRC). The performance data obtained in these tests is used for applications ranging from materials research to structural design and quality control. Designers that specify minimum levels of flexural performance for FRC when used in structural applications do this on the assumption that the results obtained from flexural performance tests represent the actual flexural performance of an FRC mixture. In reality, a considerable proportion of the apparent postcrack performance is attributable to friction at the supports. The result is that the postcrack flexural performance measured in tests may be considerably greater than the actual flexural performance of a given FRC mixture. The current research examines how friction at the supports under ASTM C1550, Standard Test Method for Flexural Toughness of Fiber Reinforced Concrete (Using Centrally Loaded Round Panel), round panel tests affects the apparent performance and variability in performance of FRC mixtures. The effect of friction was investigated by comparing results obtained using steel support plates of the type described in ASTM C1550 with results obtained using low-friction support plates. Twelve FRC mixtures were used containing a wide variety of dosages and types of fibers, thus resulting in a wide range of postcrack flexural performances. The results indicate that friction is responsible for about 12.5 % of the energy absorption or residual flexural strength obtained, but has a negligible influence on within-batch variability of test results.

Issue Section:
Technical Papers
Keywords:
fiber-reinforced concrete, friction, variability, postcrack performance, testing

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