CONSTRUCTION AND BUILDING MATERIALS, cilt.228, 2019 (SCI İndekslerine Giren Dergi)
This study investigates the effects of the hybrid use of different types of fibres in terms of their orientations, volume and hybridisation properties on the mechanical and fracture characteristics of self-compacting fibre reinforced concrete (FRC). In the experiments, three different types of macro fibres were used in two different proportions (1 or 2 vol%) to produce monotype or hybrid FRC with the same matrix phase and flowability. The fibre types used include (1) typical steel fibre, which is commonly used in many applications, (2) high-density polyethylene (HDPE) fibre with superior tensile strength, and (3) nylon fibre with characteristic diminishing effects on early and late age shrinkage. The fibre orientation was examined by image analysis and its relationship with post-cracking behaviour, which was determined by three-point flexural tests, was quantitatively evaluated. The study also evaluates and compares the orientations of different types of fibres in both monotype and hybrid FRC and reviews the interaction of fibre orientation. The results indicate that the highest flexural strength was obtained by using the nylon-steel FRC, while the HDPE-steel hybrid FRC series provided the highest fracture energy. The post-cracking residual strengths were found to have increased with increasing effective fibre reinforcement ratio, which is dependent largely on the orientations of fibres. The results of the image analysis indicate that the presence of HDPE or nylon fibres affects the orientation of steel fibres in hybrid FRC and these results were found to be in agreement with the mechanical and fracture properties of concretes. The test results demonstrate how the interactions of different types of fibres in terms of their orientations influence the flexural behaviour of hybrid FRC. (C) 2019 Elsevier Ltd. All rights reserved.