Synergistic reutilization of industrial by-product GGBS and high-water-content dredged clay waste for sustainable backfilling materials

Abstract

The extensive accumulation of dredged material waste and industrial by-product ground granulated blast-furnace slag (GGBS) has emerged as a critical environmental concern, necessitating the development of safe and sustainable management strategies for these wastes. This paper presents an experimental investigation on the evaluation of strength performance of high-water-content dredged clay treated with ground granulated blast-furnace slag (GGBS) for use as backfilling materials. A series of laboratory tests, including unconfined compressive strength (UCS) tests, direct shear (DS) tests, and scanning electron microscopy (SEM) analysis, were conducted to systematically evaluate the effects of GGBS dosage and curing time on the strength behavior of GGBS-treated dredged clay samples at varying water contents. The UCS test results indicate that all samples exhibited strain-softening behavior, with the unconfined compressive strength initially increasing and then decreasing as the GGBS content increased, peaking at an optimal dosage of 30 %. Additionally, the unconfined compressive strength consistently increased with curing time. A quantitative equation was developed to estimate the unconfined compressive strength of GGBS-stabilized dredged clay, at different curing times and water contents when the GGBS dosage is below 30 %. The DS test results demonstrate that, under a given vertical stress, the shear strength of the samples increases with both GGBS content within 30 % and curing time within 28d. The shear strength parameters, including cohesion and internal friction angle, also increased as the GGBS dosage ranged from 10 % to 30 % and the curing time extended from 3 h to 28d. Two quantitative equations were formulated to respectively estimate the cohesion and internal friction angle of GGBS-stabilized dredged clay samples at various GGBS contents from 10 % to 30 % and curing times 3 h to 28d. SEM analysis confirmed the formation of cementitious gels at higher values of GGBS dosage and longer curing time, resulting in a more uniform and denser microstructure in the treated dredged clay.