Performance Evaluation of Steel–Polypropylene Hybrid Fiber Reinforced Concrete

This paper is an experimental study on the effect of steel fibers as such, polypropylene fibers as such and when combined in hybrids on fresh and hardened properties of M40 grade concrete. The main aim is to test the workability, compressive strength, split tensile strength and flexural behaviour of concrete to the different types of fibres and volume fractions of the fibres. An equal mixture of crimped steel fibers and polypropylene fibers were used together and separately to prepare concrete mixtures at different proportions. The fresh concrete properties were also evaluated using slump and compaction factor tests, the results of which showed that workability decreased with fiber content especially the steel fiber-dominant mixes. The hardened concrete properties were tested at the following curing times namely, 7 days, 14 days and 28 days. The experimental evidence showed that there were significant differences in compressive and split tensile strengths of all fiber-reinforced mixes in comparison to conventional concrete with hybrid fiber-reinforced concrete showing the highest increase in strength. Flexural tests on beam specimens have shown improved resistance to cracks, increased ultimate load capacity and improved deflection control particularly in fiber hybrids. The interaction between steel and polypropylene fibers was found to enhance the distribution of stresses, the introduction of cracks, and ductility. On the whole, the results prove that a hybrid type of fiber reinforcement has a substantial positive effect on the mechanical performance and structural behavior of concrete and can be used in the context of better durability, strength, and crack resistance