Research on Chloride Penetration Resistance of Hybrid Fiber Reinforced Self-Compacting Concrete
The properties of chloride penetration of hybrid fiber reinforced self-compacting concrete (SCC) were investigated in this study. The results show that the chloride penetration resistance of concrete can be improved by single incorporation either carbon or cellulose fibers. The concrete chloride diffusion coefficient DRCM of 12-cm length carbon SCC with fiber content of 1.7, 2.72, and 3.4 kg/m3 decreases by 10.3, 25.5, and 18.2% compared to reference concrete without any fibers, respectively. Moreover, the concrete chloride diffusion coefficient DRCM of cellulose SCC with fiber content of 1.2, 1.6, and 2.0 kg/m3 decreases by 18.8, 22.4, and 26.7% compared to reference concrete, respectively. Based on the results of orthogonal experimental design, the chloride diffusion coefficients DRCM of hybrid fiber reinforced SCC are listed in order of importance, as follows: length of carbon fiber > content of carbon fiber > content of cellulose fiber; furthermore, the hybrid of 2.72-kg/m3 carbon fiber with length of 12 mm and 2.0-kg/m3 cellulose fiber exhibits the most significant effect on chloride diffusion coefficients DRCM of SCC.
Flexural behavior of self-compacting concrete reinforced with different types of steel fibers
The aim of the present work is to investigate the flexural behavior of self-compacting concrete reinforced with straight and hooked end steel fibers at levels of 0.5%, 1.0% and 1.5% and compare it to normally vibrated concrete (NVC). The laboratory tests were determined according to RILEM TC 162-TDF recommendation. The flexural behavior of SCC appeared to be comparable to NCV, where the increase of fibers volume ratio cause the increase in prepeak and post-peak parameters of SCC. Nevertheless, the type of steel fibers influences much this dependency. Based on the performed analysis, the flexural tensile strength of SFR-SCC can be described with the formulas used for SFRC. The equation proposed to predict the deflection-CMOD relationship of SCC fits into the coefficient of variation of the formula for NVC. However, the SCC achieves the maximum crack mouth displacement for lower deflections than NVC. The article contains also the analysis of the fracture energy of SCC with a formula to describe it.
Quality and mechanical properties of engineered steel fibres used as reinforcement for concrete
Engineered steel fibre is becoming a more and more important type of concrete reinforcement. Some applications of Steel Fibre Reinforced Concrete (SFRC) are very common in civil and structural engineering. All over the world there is a significant research effort contributing to theoretical and technological knowledge about properties and behaviour of SFRC. Nevertheless there is lack of research interest in fibres themselves. Mechanical properties and quality of fibres influence quality and performance of SFRC. Growing number of fibre producers and associated with it possible variations of quality and mechanical properties of steel fibre constituted the foundation of this research study. The most popular types of steel fibre, commercially available on the European market were chosen and tested for ductility and other properties.