Why is EN 14651 a notch beam test?
The RILEM and MC2010 design methods are based on notched beams because of the perceived benefits of notched samples. These are that the notch will provide a slower cracking process, thereby reducing the risk of a sudden drop in load. Also, notch allows the test to be controlled on the basis of the rate of increase of CMOD and the rate of increase of deflection. Furthermore, the test do not introduce structural effect. We focus on the FRC material properties.
With this issue in mind, it is essential that the design method and test method are consistent. This shows that results from different tests cannot be compared directly in some cases and especially considering hardening post crack behavior.
What is the difference between an ASTM beam test and an notch EN 14 651 beam test?
The ASTM 1609 test is performed on a beam (350mm x 100mm x 100mm or 500mm x 150mm x 150mm), without any notch, on a four-point loading configuration and it requires a servo-controlled closed-loop machine. This test is used widely in North America.
While the crack is free to occur anywhere between the third-points ( weak point), experience has shown that it tends to occur near the centre. For a centrally located crack, the maximum crack width for a deflection of 0.75mm is 1.0mm. For a centrally located crack, the maximum crack width at 3.0mm central deflection is 3.5mm.
The EN14651 is a test developed specifically to characterise FRC and derive design parameters. EN 14651 is the reference standard for the European Union CE label for steel and polymer fibres and has been adopted by a number of fibre manufacturers and designers, primarily in Europe, Asia and the Middle East. The great advantage of this test is that it relates the strength to specific CMODs (Crack Mouth Opening Displacement) and the strength indices can be used directly in design for the appropriate Limit State. This test procedure has been adopted by Model Code 2010 and its implementation is relatively straightforward and independent of the type of fibre.