Relationship between residual flexural strength and compression strength in steel-fiber reinforced concrete within the new Eurocode 2 regulatory framework

Abstract

Annex L of the next Eurocode 2 establishes a classification of the steel-fiber reinforced concrete (SFRC) by means of classes of residual flexural strength for two values of crack mouth opening displacement, 0.5 mm and 2.5 mm. Nevertheless, this indexing does not completely describe the resistance behavior of the SFRC since it does not include the residual compression strength of the material, defined as the stress resisted when the deformation is three times that reached under the maximum load [Hormigón y Acero 69:S1 (2018) 75–80], the value of which is not negligible when steel fiber is included in the concrete. The principal objective of this research consists of determining the relationship that exists between compressive and flexural residual strengths by applying the Response Surface Methodology (RSM) as an instrument of analysis. It has been performed on a combination of experimental data collected in two databases, one with compression tests and the other with flexural tests, with 484 and 197 pieces of data respectively. The classification of SFRC could be completed when the value of residual compression strength corresponding to each class of concrete given by the RSM analysis is included, thereby completely characterizing the material for the practical effects of analysis and structural design. In addition, the RSM analysis provides numerous insights on the relations of the residual strengths with the parameters of the base concrete and the fiber. The paper also provides a new cylinder/cube conversion formula based in the results of Viso, Carmona and Ruiz [Cement and Concrete Research 38 (2008) 386–395] and in the Bažant’s size-effect law, which can be used for cubes of any edge length and of any strength grade.