Effectiveness of Polypropylene Fibre on Subgrade Sand of Flexible Pavement.
Authors :- Shukla, M., Shah, J.
Publication :- Innovation in Smart and Sustainable Infrastructure, Volume 2. ISSI 2022. Lecture Notes in Civil Engineering, vol 485. Springer, 2024
The functions and properties of subgrade soil are critical for sustainable pavement infrastructure. The present study represents the performance of effectiveness of polypropylene fibre (PPF) on subgrade of flexible pavement. PPF is a kind of linear polymer synthetic fibre which is hydrophobic, non-corrosive and resistant to alkalis, chemicals and chlorides and obtained from propylene’s polymerization. In cases when the subgrade soil is poorly graded sand (SP), problems are happened related to low values of internal friction (ɸ), shear stress (τ) and California bearing ratio (CBR) if soil is not satisfied limiting criteria. The functions and properties of subgrade soil are critical for sustainable pavement infrastructure. The present study represents the performance of effectiveness of polypropylene fibre (PPF) on subgrade of flexible pavement. PPF is a kind of linear polymer synthetic fibre which is hydrophobic, non-corrosive and resistant to alkalis, chemicals, chlorides and obtained from propylene’s polymerization. In cases when the subgrade soil is poorly graded sand (SP), problems are happened related to low values of internal friction (ɸ), shear stress (τ) and California bearing ratio (CBR) if soil is not satisfied limiting criteria. This paper presents one of the studies to overcome the issues related to lose cohesionless subgrade soil by adding ppf. Randomly distributed ppf in concentration of 0.5, 1.0, 1.5 and 2.0% are mixed with sand (cohesion less soil) to obtain optimum ppf content. Effectiveness of ppf on compaction properties, shear properties and CBR of ppf reinforced sand are compared with virgin sand. Microstructure images revealed that addition of ppf beyond optimum percentage resulted in pockets of fibre and segregation of sand from the composite soil. Beyond the optimum content of ppf results fibre pockets and lumps in sand according to microstructure analysis of ppf reinforced sand. Further, flexible pavement is designed on virgin and improved soil by IRC: 37-2018 and checked by IITPAVE software. It is observed that angle of internal friction, soaked CBR and optimum moisture content (OMC) were increased by 28.74%, 40.05% and 77.26%, respectively, at optimum ppf content. While Maximum dry density (MDD) was decreased by 1.46% at optimum ppf content. The thickness of flexible pavement has been decreased by 1.51% due to addition of optimum ppf content. The shear strength is enhanced with increasing the ductility due to development of bond in between the sand particles and fibres in ppf reinforced subgrade sand. This shear strength of subgrade is useful to protect the pavement against shear failure.