Title: Experimental Investigation of Thin-Wall Synthetic Fiber- Reinforced Concrete Pipes
Author(s): Fouad T. Al Rikabi, Shad M. Sargand, John Kurdziel, and Husam H. Hussein
Publication: Structural Journal
Appears on pages(s): 1671-1681
Keywords: composite materials; concrete pipes; fiber-reinforced concrete; sewers; synthetic fiber
Synthetic fibers have been recently used to enhance the ductility, durability, flexural strength, and shear strength of concrete pipes while reducing the steel reinforcement. However, using the same pipe wall thickness specified by ASTM standards did not result in a significant enhancement in the flexibility of fiber-reinforced concrete pipe. This research investigates the effect on the flexibility, strength, stiffness, and strain capacity of using minimal steel reinforcement with the polypropylene fiber-reinforced concrete pipe with reduced wall thickness. Concrete pipes with diameters of 1200 and 1500 mm (48 and 60 in.) with respective wall thicknesses of 50 and 63 mm (2 and 2.5 in.) were tested under a three-edge bearing load. To assure maximum fiber contribution to pipe strength, a 9 kg/m3 (15 lb/yd3) fiber dosage was used with different amounts of steel reinforcement. Results showed that all tested pipes surpassed 5% deflection of their inside diameter with high load capacity. The tested pipes exhibited flexural failure, and at higher loading levels, radial and shear failure modes were also observed. Concrete pipe with a diameter of 1200 mm (48 in.) reinforced with steel area of 10.2 cm2/m (0.48 in.2/ft) fulfilled the ultimate strength requirements of ASTM for Classes I, II, and III. Also, concrete pipe with a diameter of 1500 mm (60 in.) reinforced with a steel area of 8.9 cm2/m (0.42 in.2/ft) did not fulfill the ultimate strength requirements of ASTM for Classes I and II. These pipes exhibited stiffnesses as high as 7.8 and 10.2 times that of high-density polyethylene pipe at 5% deflection for diameters of 1200 and 1500 mm (48 and 60 in.), respectively.
Increasing steel area also increased the strain capacity of the pipes. Also, comparing with past research, increasing fiber dosage from 4.75 to 9 kg/m3 (8 to 15 lb/yd3) increased the stiffness by 95%.