Direct Shear Behavior of Carbon Fiber Reinforced Self- Compacting Concrete

Abstract

This paperrepresents an experimental and statistical investigation for the behavior of connectionpoints produced by using self-compacting concrete and subjected to direct shear. The investigation also includes the effect of carbon fiber inclusion as reinforcement on self-compacting concrete (SCC) behavior in direct shear. This study gives results of sixteen push-off or direct shear specimens in four groups. Variations include volume fraction for carbon fiber (V_f= 0.00, 0.50, 0.75 and 1.00) % for every percentage change in the steel reinforcement. The steel reinforcement parameter ρ_vf f_y values are (0.00, 2.66, 5.33 and 7.99) MPa(where ρ_vf varies from 0.00 to 0.0173 and f_y=585.7MPa) . The main material properties studied include compressive strength, splitting tensile strength and modulus of rupture. Measurements of deformations were made throughout testing of shear specimens. The dimension of the shear plane in the push-off specimenswas 170x185 mm. The shear reinforcement was normal to the shear plane. Specimens were cast by using SCC which is a type of high performance concreteand reinforced with carbon fiber. This work aims to investigate the direct shear behavior of SCC with or without carbon fiber at constant water to cementitious materials ratio of 0.3 by weight. It is found that using carbon fiber increased the direct shear strength. However, carbon fiber alone (without reinforcement) leads to brittle failure. In contrast, adding rebars leads to higher strain and more ductile behavior-increased shear capacity is obtained when higher steel quantity is used. The aim of adding carbon fibers was the increase of the horizontal strain (displacement). It was found that the optimum percentage of volume fraction was 0.75 % for fresh and hardened concrete. In addition, the effects of carbon fiber on compressive strength of SCC lead to a drop in compressive strength (f_c^') compared with reference specimens. This drop in f_c^' was 2.39, 8.38 and 13.58% for V_f=0.50, 0.75 and 1.00%, respectively. In contrast, the splitting tensile strength increased by 3.34, 31.2 and 18.2 as compared with the cylinder strength without carbon fibers atV_f equal to0.50, 0.75 and 1.00% respectively. The modulus of rupture increased by [11.9, 21.99 and 13.83%] as compared with SCC without carbon fibers at〖 V〗_f equal to 0.50, 0.75 and 1.00% respectively. Based on push-off tests results for this work and those available in the literature, two statisticalmodels have been established using regression analysis. Four variables f_c^',f_ct,ρ_vf f_y and V_f, were included in these models. Both models showed good representation according to their coefficients of variation (COV)values. Verification of the models were done by using 273 observations from literature and the present work.

Keywords

• direct shear
• self
• compacting concrete
• carbon fiber
• reinforced concrete