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This paper presents an experimental investigation of how varying the volume fraction of chopped basalt fibers affects the mechanical properties of fiber‐reinforced concrete (FRC). The fiber content is varied in the range of 0–2%. The main parameters investigated are workability, compressive strength, splitting tensile strength, flexural strength, and flexural toughness. Test results showed that the compression strength of concrete decreased marginally with the addition of basalt fibers in comparison with plain concrete. However, the mode of failure of FRC under compression is changed from the brittle to ductile. The splitting tensile strength of concrete is improved by 15% when basalt fibers with 2% volume fraction are added to the concrete mix. A significant increase of up to 75% is noticed in the flexural tensile strength of basalt FRC, with better post‐peak residual strength compared with the plain concrete. Furthermore, the flexural toughness of basalt FRC is increased by nearly three times that of the plain concrete based on the round panel tests.

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SUMMARYSteel caging technique is commonly used for the seismic strengthening of reinforced concrete (RC) columns of rectangular cross-section. The steel cage consists of angle sections placed at corners and held together by battens at intervals along the height. In the present study, a rational design method is developed to proportion the steel cage considering its confinement effect on the column concrete. An experimental study was carried out to verify the effectiveness of the proposed design method and detailing of steel cage battens within potential plastic hinge regions. One ordinary RC column and two strengthened columns were investigated experimentally under constant axial compressive load and gradually increasing reversed cyclic lateral displacements. Both strengthened columns showed excellent behavior in terms of flexural strength, lateral stiffness, energy dissipation and ductility due to the external confinement of the column concrete. The proposed model for confinement effect due to steel cage reasonably predicted moment capacities of the strengthened sections, which matched with the observed experimental values.

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