Abstract
In the present study, an experiment was conducted to investigate the mechanical properties such as fluidity, compressive strength and flexural performance (flexural strength and toughness) of a single fiber-reinforced mortar (FRM) using only macro steel fiber (SF) or micro carbon fiber (CF) with different material properties and SF-CF hybrid FRM using a mixture of macro SF and micro CF. The specimens incorporated macro SF and micro CF in the mix proportions of 100-0%, 75-25%, 50-50%, 25-75% and 0-100% by volume at a total fiber volume fraction of 1.0%. Their mechanical properties were further compared and reviewed with the plain mortar at 28 days of age. The experimental results of fresh mortar showed that the table flow of mortar using only macro SF was slightly reduced compared to plain mortar, whereas the table flow of mortar using only micro CF and SF-CF hybrid mortar decreased significantly with increase of micro CF. It was revealed from the test of the hardened mortar that the SF-CF=75-25% (M3) specimen showed the highest compressive and flexural strength, and the SF-CF=50-50% (M6) specimen obtained the highest flexural toughness. Therefore, it was possible to confirm the synergistic reinforcement effect of that enhanced the strength and improved the flexural performance by hybrid of macro SF and micro CF. Based on the results of this experiment, the optimal mix proportion of SF-CF hybrid FRM is proposed in this paper to improve the compressive strength, flexural strength and flexural toughness.
Highlights
Cement-based composite materials have been used worldwide as major construction materials for buildings and civil engineering structures till due to their excellent compressive strength [1,2,3]
fiber-reinforced mortar (FRM) using only macro steel fiber (SF) or micro carbon fiber (CF) and an SF-CF hybrid FRM using a mixture of macro SF and micro CF at a total fiber volume fraction of 1.0% were experimentally reviewed
The mixture ratio showing the lowest fluidity in the SF-CF hybrid mortar proportion was SF-CF=25-75%, revealing that micro CF, unlike macro SF, was found to cause a large decrease in fluidity compared to other mortar mixtures because it has a high fiber aspect ratio and absorbs part of the mixing water
Summary
Cement-based composite materials have been used worldwide as major construction materials for buildings and civil engineering structures till due to their excellent compressive strength [1,2,3]. Cement-based composite materials have two well-known disadvantages that they are vulnerable to flexural·tensile strength, and have brittle properties including low ductility and lack of strain capacity. This is why studies have been continuously conducted on fiber-reinforced cement composites (FRCC) in which discontinuous and short fibers are irregularly dispersed in the cement composite in order to improve the disadvantages of such brittle properties [4,5,6]. Only single fibers have been limitedly used for FRCC in general, various studies are being conducted on hybrid fiber-reinforced cement composites (HyFRCC) that can maximize the effects which single fibers cannot exert by mixture of two or more types of fibers having different material properties in an appropriate ratio. In case of HyFRCC with different material properties, effects which are
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