Performance comparison of polypropylene and elastic fibers in enhancing the flexural behavior of lime-stabilized kaolinite clay

Abstract

The use of fiber reinforcement to improve soil characteristics is widely accepted in geotechnical engineering. Current research introduces a novel elastic fiber (E fiber) aimed at enhancing the flexural characteristics of untreated and stabilized kaolinite clay, comparing its performance with that of the more well-known polypropylene fiber (PP fiber). The E fiber features a composite structure consisting of a core made of a larger spandex fiber, known for its high elasticity, surrounded by numerous finer polyester fibers. As a byproduct of the textile industry, E fiber is cost-effective, environmentally sustainable, and its larger dimensions facilitate mixing with soil compared to PP fibers. Kaolinite samples were treated with 1 %, 3 %, and 5 % lime (L) and reinforced with 0.15 %, 0.25 %, and 0.35 % PP fibers or 1.5 %, 2.5 %, and 3.5 % E fibers, with consistent lengths of 6 mm and 12 mm. All samples were cured at 20–25 °C for 7 and 28 days. For quantitative and qualitative assessment of fiber performance, three-point bending (TPB) tests and Scanning Electron Microscopy (SEM) analyses were conducted. Results indicated that reinforcement and stabilization, whether independently or concurrently applied, significantly increased the peak force (P) and deflection at peak load (Δ) of the samples. A direct relationship between P and Δ with the fiber content, fiber length, lime dosage, and curing duration was observed. Importantly, at the same lime content and curing periods, both E and PP fibers exhibited similar ranges and averages for load (α) and ductility (β) improvement coefficients. Thus, it is concluded that the performance of PP and E fibers is approximately similar in enhancing flexural strength and ductility. Consequently, E fiber can be considered a promising candidate for reinforcing untreated and lime-treated clay. However, it is recommended that before using E fiber in field projects, its performance in reinforcing other soils stabilized with different binders and subjected to varying environmental and loading conditions be investigated.