Engineering Characteristics of Rubber-Added Lightweight Soil as a Flowable Backfill Material

This study investigated the engineering characteristics of rubber-added lightweight soil (RLS), which consists of dredged soil, crumb rubber, and bottom ash. RLS is considered to be environmentally friendly because it provides a means to recycle dredged soil, rubber, and bottom ash. It can be characterized as a flowable backfill material with a light unit weight, resulting from the slurried mixture with rubber. In this study, several kinds of specimens were prepared with seven different water contents (140–200% at 10% intervals) and five different rubber contents (0–100% at 25% intervals by dredged soil weight) and subjected to flow testing to investigate the flowability of the slurried mixtures. Unconfined compression tests were also carried out to evaluate the mechanical properties of RLS, including bulk unit weight, strength, and secant modulus. Test results revealed that the unconfined compressive strength and unit weight of RLS decreased as rubber content increased, but axial strain at peak increased. Additionally, the stress-strain relationship of RLS exhibited ductile rather than brittle behavior owing to the inclusion of the rubber.