Open Access

ARTICLE

Shape-Effect in the Effective Laws of Plain and Rubberized Concrete

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1 DICAM, Facoltà di Ingegneria, Alma Mater Studiorum, Università di Bologna, Viale Risorgimento 2, 40136 (BO), Italy.

Computers, Materials & Continua 2012, 30(3), 237-284. https://doi.org/10.3970/cmc.2012.030.237

Abstract

The procedure of the effective law outlined in this paper [Ferretti (2001); Ferretti and Di Leo (2003); Ferretti (2004b)] is an experimental procedure for identifying the constitutive law in uniaxial compression of brittle heterogeneous materials, and is based on the physical, analytical and numerical discussions about the existence or otherwise of strain-softening [Ferretti (2004a); Ferretti (2005)]. This procedure allows us to correct several incongruities that characterize the average stress versus average strain diagrams: it produces evidence against strain-softening in uniaxial compression [Ferretti (2004b)], whose existence may be questioned from a physical point of view [Ferretti (2004a); Ferretti (2005)], it provides effective stress versus effective strain laws that are size-effect insensitive [Ferretti (2004b)] and identifies Poisson's ratio and volumetric strain, which are independent of the degree of damage during the compression test [Ferretti (2004c)], as should be the case for all constitutive parameters. The procedure also allows us to explain the gradual change of shape in the average stress versus average strain laws when a confinement pressure is applied to the specimen [Ferretti and Di Leo (2003)]. Moreover, the procedure emphasizes how the final stage in compressed concrete specimens is largely characterized by the propagation of a macro-crack, rather than by crushing. This puts a question mark on the existence of creep, which, according to the identified effective parameters, seems mainly to be a structural effect due to crack propagation [Ferretti and Di Leo (2008)]. In this paper, the identification procedure of the effective law is applied to cubic and cylindrical concrete specimens, in order to verify whether or not the effective law is sensitive to shape-effect. Two different concrete mixtures were used, the one of plain and the other of rubberized concrete. New relationships were also proposed for design purposes, both for plain and rubberized concrete.

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