Issue 31

A. Abrishambaf et alii, Frattura ed Integrità Strutturale, 31 (2015) 38-53; DOI: 10.3221/IGF-ESIS.31.04 39 In this research, the effect of fibre distribution and orientation on the tensile behaviour of a SFRSCC panel is investigated. For this purpose, a total number of 46 cores were extracted from various locations of two panels. These cores were subjected to indirect (splitting) and direct (uniaxial) tensile tests. In order to assess the influence of fibre distribution/orientation on the tensile post-cracking parameters, specimens were notched either parallel or perpendicular to the expected concrete flow direction. Furthermore, fibre distribution parameters were evaluated through an image analysis procedure. Finally, the local stress-crack opening relationship ( σ – w ) was obtained by modelling the splitting tensile test under the finite element framework and by performing an Inverse Analysis (IA) procedure. Afterwards the σ-w law obtained from IA is then compared with the one ascertained directly from the uniaxial tensile tests. E XPERIMENTAL PROGRAM Concrete mixture steel fibre reinforced self-compacting concrete was design with 60 kg/m 3 of hooked-end steel fibres (length, l f , of 33 mm; diameter, d f , of 0.55 mm; aspect ratio, l f /d f , of 60 and a yield stress of 1100 MPa).The mixture constituents are: cement (C), water (w), limestone filler (F), fine sand (FS), coarse sand (CS), coarse aggregate (CA) and superplasticizer (SP). Tab. 1 includes the adopted concrete mix composition. In order to evaluate the flowability of the concrete, the slump test was performed according to the EFNARC recommendations [10]. The total spread achieved on the slump test was about 670 mm. The Young’s modulus and compressive strength were assessed on cylinders with a diameter of 150 mm and height of 300 mm. The average compressive strength ( f cm ) and the average value of the Young’s modulus ( E cm ) were 47.77 MPa (7.45%) and 34.15 GPa (0.21%), respectively, in which the values in parentheses represent the coefficient of variation. C [kg] W [kg] SP [kg] F [kg] FS [kg] CS [kg] CA [kg] Fibre [kg] 413 140 7.83 353 237 710 590 60 Table 1 : Mix composition of steel fibre reinforced self-compacting concrete per m 3 . 1600 (mm) 1000 (mm) 1600 (mm) 1000 (mm) (a) (b) Figure 1 : Core extracting plan: (a) panel A, (b) panel B. Specimens According to Barnett et al. [11] casting panels from its centre point can improve the mechanical behaviour, when comparing to other casting methods. Thus this method was selected for the production of two panels. The dimensions of the panels were 1600×1000×60 mm 3 . In order to evaluate the influence of fibre dispersion and orientation on the tensile properties of the SFRSCC, twenty three cores were extracted from each panel, and submitted to either indirect (splitting) or direct (uniaxial) tensile tests. The specimens were extracted according to the scheme represented in Fig. 1. In this figure the pale dash lines with arrows represent the supposed concrete flow directions. The hatched cores were used in the splitting tensile tests and the remaining was used in the uniaxial tensile tests. For the execution of the splitting tensile tests, two notches were executed on the cores’ opposite sides with the depth of 5 mm. In order to evaluate the influence of crack orientation towards the concrete flow, specimens were notched either parallel or perpendicular toward the expected A