Identification of tensile constitutive parameters of High Performance Fibre Reinforced Cementitious Composites (HPFRCCs) via the Double Edge Wedge Splitting (DEWS) test: conventional vs. Digital Image Correlation measurements

Experimental identification of the tensile constitutive relationship of fibre reinforced cementitious composites is the foremost step in the definition of a design approach for structures made of, or retrofitted with, the aforementioned category of advanced cement based materials. A test has been proposed and validated in the past years for the identification of the tensile behaviour of HPFRCCs and called Double Edge Wedge Splitting test (DEWS), which, though being an indirect test, is deemed to yield straightforward the constitutive tensile behaviour of the material. With classical deformation/displacement measurement and acquisition techniques, the whole set of measuring instruments, besides requiring a multichannel dedicated acquisition system, which is not instrumental to the test ease of execution, may also result excessively cumbersome for the specimen dimensions. Furthermore, because of the unique behaviour of the material, which may be able to keep a not negligible residual load bearing capacity up to quite large crack openings, loss of contacts or attainment of limits of measuring instruments can even occur, thus partially jeopardizing the completeness of the information that the same instrumentation was aimed to garner. In this paper a series of DEWS tests has been performed on square specimens wide different dimensions and made with a High Performance Fibre Reinforced Cementitious Composites. Specimens have been cut from larger slabs. The survey and measurement of the displacements have been made both by LVDTs on either face of each specimen and by DIC of images taken by a camera on one face of the same specimen. The comparison of the measurements obtained by both methodologies together with a “tailored” analysis of the information provided by the processing of DIC results will support the effectiveness of the DIC as a displacement measuring procedure and also contribute towards the development of only-DIC monitored tests in the field of experimental testing of concrete and advanced cement based materials and structures.