Experimental Study on Shear Strength of Synthetic Fiber Reinforced High Strength Concrete Containing Slag Aggregate

Slag aggregate has been used extensively in the concrete mixtures as coarse aggregate due to its economic and environmental benefits, especially in the north of Ohio, where steel factories produce a high amount of it. To improve the mechanical properties of concrete such as flexural, shear, and tensile strength, synthetic fibers have been used for decades. However, there are limited studies regarding the shear performance of slag aggregate concrete reinforced with synthetic fiber. The objective of this study is to evaluate the performance of synthetic fiber reinforced concrete beams under pure shear loading. Fiber contents of 0.25, 0.5, 0.75, and 1.0% with three different lengths, 0.75 in. (19 mm), 1.5 in. (38 mm), and 2.25 in. (57 mm) were used to investigate the effects of fiber length and content on the shear performance of concrete. Concrete prisms with a dimension of 3×3×14 in. (75×75×356 mm) (width×depth×length) were tested. An innovative test method was utilized to apply a pure shear force on the concrete specimens. Results showed that using synthetic fiber improved the shear strength of slag aggregate concrete specimens. This improvement was proportional to the fiber content and length. As the fiber content increases, the post-cracking behavior enhanced due to the increase the number of fiber bridging propagate cracks. It was observed that fiber length has a significant impact on the post-cracking behavior. As the fiber length increases, it was observed that tested specimen sustained load even though the crack width increased. This behavior mainly is attributed to that long fibers have more embedded length compared to the short fiber, resulting in higher bond strength and higher post cracking. Also, it was observed that specimens reinforced with fiber length of 1.5 in. and 2.25 in. (38 and 57 mm) experienced fiber pull out and breakage. On other hand, specimens reinforced with fiber length of 0.75 in. (19 mm) experienced fiber pullout. Therefore, it is recommended using fiber with a concrete mixture containing slag as coarse aggregate due to its high impact on the shear performance.