Investigation of rheological, mechanical, fracture parameters and optimum design of steel fiber reinforced self compacting concretes

The effects of steel fiber content, fiber aspect ratio and fine to coarse aggregate ratio on the rheological, mechanical and fracture properties of steel fiber reinforced self compacting concrete (SFRSCC) has been the topic of this experimental study. Also, optimization and performance based design of SFRSCC mixtures were investigated within the scope of this research.The rheological characteristics of plain and steel fiber reinforced self compacting concrete mixtures were investigated by slump-flow, J-ring, V-box and L-box test methods. The mechanical properties such as compressive strength, modulus of elasticity, splitting tensile and flexural strength and some of the fracture parameters such as fracture energy have been determined for all plain and SFRSCC mixtures.Fracture energy of all mixtures was measured by a closed-loop bending test device on notched samples under three-point loading system. Also the effect of fiber orientation on fracture parameters was investigated by a computer-aided image analysis technique.An optimization technique, ?Response Surface Methodology, RSM? which is widely used in optimum design of chemical products, has been adopted for use in the optimization of SFRSCC mixtures. Mechanical properties, cost and workability of SFRSCC mixtures were the main parameters in the optimization process. Furthermore, optimum fiber content and fine to coarse aggregate ratio for various SFRSCC mixtures corresponding to a certain amount of fracture energy has been determined by a performance based design considering rheological properties besides mechanical and fracture parameters.Experimental studies showed that, fine to coarse aggregate ratio is a significant property in the design of SFRSCC mixtures. Test results also indicated that in order to obtain the best rheological, mechanical and fracture properties, optimum fine to coarse aggregate ratio depends on the fiber aspect ratio.