Expansion characteristic of steel slag mixed with soft clay

Abstract

The heavyweight characteristic of steel slag gives it the potential to be used in various civil engineering constructions. However, controlling its volume instability is challenging. In this paper, we aim to comprehend the expansion mechanism of steel slag mixed with soft marine clay and determine the maximum steel slag addition needed to achieve a heavyweight geomaterial still in compliance with the allowable expansion. A series of expansion tests on steel slag mixed with soft clay were performed and evaluated. Scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) were conducted to support the tests. Our results showed that the removal of fine content in steel slag is not effective for alleviating expansion. In the steel slag mixed with soft clay, the soft clay provided spaces that absorbed the volumetric change of the steel slag, and 60% was found to be the maximum volumetric addition to the soft clay, exhibiting 0.24%–0.35% of the volumetric expansion. The addition of 60% of steel slag produced 24.3 kN/m3 of unit weight, which is preferable for certain submerged fill purposes. SEM and EDS analysis results showed more microcracks and less existence of the C-S-H phase in 45%–60% of steel slag addition than in 70–100%, which explains the occurrence of less volumetric expansion.