ASTM C1550-20 PDF Download

ASTM C1550-20 is a standard test method that is used to determine the flexural toughness of fiber-reinforced concrete. The test is carried out using a centrally loaded round panel, which is supported on three pivots arranged symmetrically around its circumference. This test configuration allows the panel to experience bi-axial bending and simulate the post-crack behavior of plate-like structural members.

The test measures the energy absorbed by the panel up to a specified central deflection, which represents the ability of the fiber-reinforced concrete to redistribute stress after cracking. The energy absorption is related to the toughness of the material and can vary depending on the intended application. For example, a central deflection of 5 mm may be suitable for situations where the material needs to hold cracks tightly closed, while a central deflection of 40 mm may be more appropriate for situations with severe deformation.

The use of a round panel with three supports has been found to provide within-batch repeatability and consistent failure mode. The round panel configuration eliminates the need for sawing and allows for easier preparation of specimens. The nominal dimensions of the panel are 75 mm in thickness and 800 mm in diameter, although correction factors are provided to account for actual measured dimensions.

It is important to note that the size and characteristics of the aggregate and fibers used in the concrete may influence the post-crack behavior. In particular, larger aggregate particles or longer fibers may result in different performance. The test method acknowledges these influences and accepts that no single test specimen can perfectly represent all structural sizes. The method is more representative of in-situ behavior when applied to specimens produced by spraying (shotcreting) rather than casting concrete.