This study evaluates the size effect of shear strength in reinforced concrete (RC) beams with various replacement ratios of recycled coarse aggregate. A total of 15 simply supported specimens with recycled aggregates were cast and tested in shear. The test variables were designed to be the width and effective depth of the beam and the replacement ratio of recycled coarse aggregate. The width of the specimens was varied from 200 mm to 400 mm, and the effective depth was changed from 300 mm to 600 mm. To estimate the size effect of shear strength in recycled aggregate concrete beams, the specimens had no shear reinforcement. The experimental results showed that the shear strength of the specimens made of recycled aggregate decreased with a higher effective depth irrespective of the replacement ratio, whereas the beam width exhibited no size effect. Furthermore, the strength reduction and crack patterns of the specimens with recycled aggregates were similar to those of the specimens with natural aggregates.

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This study estimates the flexural performance of reinforced concrete (RC) beams with electric arc furnace (EAF) oxidizing slag aggregates. EAF oxidizing slag is a byproduct of steel production. It is composed mainly of CaO and SiO 2 , which are similar to the chemical properties of natural aggregates. Simply supported RC beams having various types of aggregates were tested to evaluate the applicability of EAF oxidizing slag as a concrete aggregate. The moment-curvature relationship and crack patterns up to peak load as well as the effective moment of inertia and deflection of the specimens under service load were analyzed and compared with the experimental results of natural aggregate specimens. The experimental results showed that the specimens with EAF oxidizing slag aggregates exhibited similar flexural performance to that of the specimens with natural aggregates.Keywords: flexural behavior; bending moment; reinforced concrete beams; electric arc furnace slag aggregate IntroductionT h e g r o w t h o f t h e s t e e l i n d u s t r y h a s b e e n progressing steadily as civilization progresses. The steel industry has also generated innumerable varieties of byproducts and waste with the mass consumption of energy and raw materials. In particular, the amount of slag, the most dominant byproduct of steel and iron smelting operations, is increasing each year, thus heightening the need for devising effective recycling methods.

This study evaluated the pure confinement effect of steel spirals embedded in concrete with varying compressive strengths. The experimental variables in the study were the compressive strength of concrete and the yield strength and volumetric ratio of the steel spirals. To estimate the pure confinement effect of the steel spirals, all the specimens were designed to exclude concrete cover and longitudinal reinforcement. The experimental results showed that the confinement effect of spirals increased with yield strength and volumetric ratio of the spirals, but greatly decreased as the concrete compressive strength increased. Using the relationship between axial and lateral strains at peak stress of spirally confined concrete, an analytical model was developed to predict the stress–strain relationship of confined concrete. The proposed model can be successfully used to predict the structural behaviour of concrete confined by normal-, high- and ultra-high-strength steel spirals, regardless of the compressive strength of concrete.

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