1. IntroductionStainless slag is a by-product of stainless steel production. In Japan, approximately 30,000 tons of stainless slag are produced each year. The authors studied the basic physical properties of concrete used with stainless slag as fine aggregates and concluded that stainless slag can be used as fine aggregates in concrete up to 60% in proportion of the mixture without any caution. This study aims to effectively use stainless slag as a structural concrete material. In order to promote stainless slag as fine aggregates for structural purposes, the behavior and performance of simple RC beams using stainless slag were investigated experimentally. In the loading test experiment, the mechanical response behavior due to cracking, deflection and resistance between using stirrups and without stirrups was measured.2. Experimental procedures 2.1 Proportions of material and mixtureTable 2. Description of reinforcementType Elastic modulus Yield strength Area Remark (kN/mm2) (N/mm2)Ø6 120 388 63.67 stirrupD 16 200 350 397.2 tendonTable 1 shows the properties of concrete materials. Ordinary Portland cement with a density of 3.15 g/cm3 was used. The sea sand comes from the Genkain Sea located in Fukuoka Prefecture and has a dry density of 2.57 g/cm3, water absorption of 1.62% and fine modulus of 2.85. Stainless steel slag which is a by-product of stainless steel production, with physical properties, oven dry density of 3.04 g/cm3, surface dry density of 3.08 g/cm3, a water absorption of 1.53% and a fineness modulus of 2.96, including 1.96% fineness material. . The reinforcement consists of a D16 mm deformed bar and a Ø6 mm plain bar as stirrups, as shown in Table 2. Table 3 shows the mixing proportions and fresh properties of the concrete used in this experiment. Both...... middle of paper ...... slight difference between two stainless slag compositions. (2) The deflection of the beams shows that the RC beams contain higher stainless slag than the RC beams without containing stainless slag at the yield point. for beam using stirrups. However, for beams without stirrups, RC beams contain stainless slag slightly similar to RC beams without stainless slag (3). The crack occurs earlier on the beam without stirrups than on the beams with stirrups. On the other hand, the loading pressure of RC beams containing stainless slag is slightly higher than that of RC beams without stainless slag on the loading date, including the amount of crack occurred.5. Reference (1) JSCE Directive for Concrete no. 15 (2007) Standard Specification for Concrete Structures-2007 “design” English version(2) 浦木 大資, 高海 克彦, 松尾 栄治 (2013),基礎物性に関する研究(3) 徳重裕平, 松尾栄治, 高海克彦, 王亮 (2012),