This study proposed a new method to confine concrete cylinders or reinforced concrete columns using martensite shape-memory-alloy wires. The prestrained martensite SMA wire wrapped a concrete cylinder and, then, was heated by a heating jacket. In the process, the confining stress around the cylinder was developed in the SMA wire due to shape memory effect, which can increase the strength and ductility of the cylinder under axial compressive load. In this study, 1mm diameter of martensite SMA wire was used for confinement. The transform temperature of Mf and Af of the SMA were 37℃ and 84℃, respectively. The cylinders had the length of 300 mm and the diameter of 150 mm. The space between wrapping wires was 2 mm. The unconfined concrete cylinders were tested and their results were compared to those of the confined cylinders with SMA wires. The SMA wire increased the compressive strength and the ductility of the cylinders due to confining effect. After the compressive load, the cylinder was bulged and the SMA wire was strained. At the state, the wrapped cylinder was heated by the heating jacket. Then, a portion of the bulge of the cylinder was recovered and the cylinder showed good strength and ductility in the second compressive test. The study showed the potential of the proposed method to retrofit reinforced concrete columns using SMA wires to protect themselves from an earthquake. KEY WORDS: shape memory alloy, martensite, shape memory effect, concrete, retrofit

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