Stress-Strain Characteristics of Fiber-Reinforced Rice Husk Ash: Fid-Bau Portal

Stress-Strain Characteristics of Fiber-Reinforced Rice Husk Ash

Jha, J.N. / Gill, K.S. / Choudhary, A.K. / Shukla, S.K.

The availability of traditional materials such as soils and rocks for geotechnical applications is becoming increasingly scarce and there is a need to search for economically viable substitutes for these traditional materials. Rice husk ash is a waste produced from the burning of rice husk and it can be one of the substitutes for traditional materials. Moreover, the utilization of rice husk ash is one of the possible ways to solve the environmental and disposal problems being created by the ash. Rice husk ash, if reinforced with certain kind of discrete fibre reinforcing material, may provide an economically viable and environment-friendly alternative to many other geotechnical problems. Since the discrete fibres can be easily added randomly to the soil as other additives such as cement and lime, they offer strength isotropy and limit potential planes of weakness that can develop parallel to the oriented reinforcement as included in systematically reinforced soil. However, very limited information has been reported on randomly distributed fiber-reinforced rice husk ash (RHA) in the literature. This paper presents the relative efficiency of reinforcement used in improving the shear strength of RHA. A series of tri-axial tests were conducted with specimens of both unreinforced RHA as well as RHA reinforced with fibres.Two different types of fibers, namely: commercially available polyethylene fibers and fibers of waste geogrid (obtained after cutting the used geogrid available in the laboratory generally discarded as the waste) having different fiber contents (0.25- 1.50% of dry weight of RHA) were used in the presenr investigation. The results have been analyzed, and it is observed that inclusion of reinforcement in general increases the shear strength of RHA but the reinforcing efficiency of these fibers depends mainly on the fiber type,fiber content and the confining pressure. Based on the result and discussion presented, the following general conclusions can be drawn: (1) Mixing of synthetic fibers can increase the strength of rice husk ash (RHA), but there exists an optimum fiber content at which reinforcement benefits are maximum. In the present study the optimum fiber content is 1.25%. (2) The stress-strain behaviour of RHA improves considerably due to an increase in fiber content. Elastic moduli increase with an increase in fiber content. (3) Secant modulus of reinforced RHA increases with an increase in fiber content up to 1.25% and thereafter it decreases. (4) Shear strength parameters (cohesion and angle of internal friction) also increase with an increase in fiber content up to 1.25% and thereafter they decrease. (5) Although polyethylene fibers have greater reinforcing efficiency, but the use of waste geogrid fibers may be economical for low-cost civil engineering projects.