Double edge wedge splitting (DEWS): an indirect tension test to identify post-cracking behaviour of fibre reinforced cementitious composites

Experimental identification of the tensile constitutive behaviour of fibre reinforced cementitious composites represents a foremost step in design approaches for structural elements made with this kind of advanced construction materials. To this purpose, international standards and guidelines recommend either direct tension or/and bending tests, coupled with an inverse analysis procedure, both featuring pros and cons which have been exhaustively highlighted and discussed in these last years. The tremendous developments of self compacting fibre reinforced concretes have furthermore highlighted the need of duly taking into account, within the aforementioned identification procedure, the likely flow-induced alignment of fibres with the applied tensile stress. In this paper a novel experimental testing technique, called double edge wedge splitting test, has been presented and validated, also by means of nonlinear finite element analysis. The test, as it will be shown, is able to yield directly, i.e. with no need for back analysis, the tensile stress versus crack opening "constitutive relationship" of the material, though performing an "indirect" test, i.e. by applying a compressive load to the specimen. Both the simplicity of the indirect tensile testing technique and the straightforwardness of the identification procedure surely represent a distinctive and extremely attractive characteristic of the proposed test. Furthermore, the test features a compact specimen geometry, which can be even easily "cored" from existing structures, and a "notch preordained" fracture plane, which can be aligned to any desired angle with respect to the expected flow-induced fibre orientation. This makes the proposed test suitable for a thorough characterization of the influence of fibre orientation on the material constitutive behaviour, as it may be required by a casting process tailored to the intended applications.