Effect Of Hybrid Fibers Research Articles

Tension Stiffening and Cracking of Hybrid Fiber-Reinforced Concrete

An experimental program has been carried out to study the effect of hybrid fibers on the tension stiffening and cracking characteristics of high-performance concrete (HPC). A total of 24 axially reinforced concrete tension members were cast and tested under uniaxial tension. The main variables considered were the volume fraction of: 1) crimped steel fibers (0.5 and 1.0%); and 2) polypropylene fibers (0.1, 0.15, and 0.2%). Load-deformation response was recorded and analyzed. Crack width and crack spacing were also measured at all stages of loading. Test results indicate that the addition of fibers in hybrid form significantly improves the tension stiffening effect and resistance to cracking. The combination of 1% steel fiber and 0.1% polypropylene fiber showed better performance than the other combinations considered in this study. A method is proposed to predict the crack width of hybrid fiber-reinforced, high-performance concrete tension members, and the computed values compared satisfactorily with the test results.

The effect of hybrid fibers and expansive agent on the shrinkage and permeability of high-performance concrete

In this paper, high-performance concrete (HPC) incorporated with expansive agent and hybrid fibers, i.e., steel fibers, polyvinyl alcohol fiber (PVA fiber), and polypropylene fiber (PP fiber), was produced. The properties measured included shrinkage and water permeation of the concrete. The effect of hybrid fibers and/or expansive agent on the shrinkage and water permeation properties was investigated. Test results indicated that the hybrid fibers of different types and sizes could reduce the size and amount of crack source at different scales; hybrid fibers combined with expansive agent provided better enhancement for shrinkage resistance and impermeability of HPC than monoincorporation of hybrid fibers or expansive agent; the improvement of the shrinkage resistance and the impermeability of the concrete resulted from the combined use of expansive agent and hybrid fibers, which was dependent on the amount of expansive agent, types and sizes of hybrid fibers, total volume fraction of fibers, proportions of hybrid fibers, and so on. The relevant mechanisms were also discussed based on the analysis of the test results of pore structure of the concrete.

Fracture properties of concrete reinforced with steel–polypropylene hybrid fibres

This research discusses polypropylene fibres and three sizes of steel fibres reinforced concrete. The total fibre content ranges from 0% to 0.95% by volume of concrete. A four-point bending test is adopted on the notched prisms with the size of 100×100×500 mm 3 to investigate the effect of hybrid fibres on crack arresting. The research results show that there is a positive synergy effect between large steel fibres and polypropylene fibres on the load-bearing capacity and fracture toughness in the small displacement range. But this synergy effect disappears in the large displacement range. The large and strong steel fibre is better than soft polypropylene fibre and small steel fibre in the aspect of energy absorption capacity in the large displacement range. The static service limitation for the hybrid fibres concrete, with “a wide peak” or “multi-peaks” load–CMOD patterns, should be carefully selected. The ultimate load bearing capacity and the crack width or CMOD at this load level should be jointly considered in this case. The K IC and fracture toughness of proper hybrid fibre system can be higher than that of mono-fibre system.