Effect of graded fibers on stress strain behaviour of Glass Fiber Reinforced Concrete in tension

Effective blending of short length and long length fibers in concrete is termed as Graded fiber reinforced concrete. Earlier research shows that short length fibers primarily control the propagation of micro cracks, and improve the ultimate strength whereas, long length fibers arrest the macro cracks and improve the post crack deformation of concrete. Thus different combinations of short and long length fibers would help in arresting the micro and as well as macro cracks to improve both pre and post crack performances of concrete. An attempt has been made to study the effect of addition of Graded Glass Fibers with different fiber length and volume fraction in Glass Fiber Reinforced Concrete. The experimental work was carried out under uni-axial tension for M30 grade of concrete with the 0.1%, 0.2%, 0.3%, 0.4% & 0.50% fiber volume of Mono Glass Fibers (3 mm, 6 mm, 12 mm and 20 mm length fiber). In 0.3% fiber volume, different fiber volume combination of Glass fibers in Short Graded form (3 mm + 6 mm length fiber), combination of Glass fibers in Long Graded form (12 mm + 20 mm length fiber) and combination of Short Graded + Long Graded fibers to form Combined Graded fibers (3 mm + 6 mm + 12 mm + 20 mm length fiber) were studied. The results shows that the strength, deformation capacity and energy absorption capacity is higher for Graded Glass Fiber Reinforced concrete than Mono Glass Fiber Reinforced Concrete. Graded fibers improved the workability. Fiber efficiency characteristics (Fiber length, Fiber dispersion, fiber orientation) were quantified to investigate their effect on the tensile strength of Glass Fiber Reinforced Concrete (GFRC). For this purpose, optical microscopic study and an image analysis technique is used to examine the failed specimens of GFRC. The results of image analysis shows that the strength of fiber reinforced composite are dependent on the fiber efficiency characteristics.