Seawater effects on ground granulated blast furnace slag (GGBS)-stabilized marine deposits in land reclamation

Abstract

<p>Lime-activated ground granulated blast furnace slag (GGBS) is an eco-friendly alternative to cement for soil stabilization, with significant potential for land reclamation applications. However, the effects of seawater on the strength and durability of lime-GGBS-stabilized soil are limitedly studied. This study aims to find the optimal formula of GGBS and lime for land reclamation, incorporating seawater curing to examine its impact on the strength and durability of lime-GGBS-stabilized soil. Unconfined compression tests were performed on soil specimens with varying GGBS and lime contents under different curing conditions. The results show that specimens with higher amounts of lime exhibit higher early strength due to accelerated reactions caused by the hydration heat. However, excessive lime when curing in the curing box causes carbonation, in which the atmospheric CO₂ is absorbed into the pore solution, neutralizing the alkaline environment, thus slowing further strength development. This behavior is consistent with X-ray diffraction (XRD) results, in which more calcite is observed in specimens with higher lime content. The strength of specimens with GGBS content of 10% reduces by around 40% from 28 to 90 days in the seawater, which can be attributed to the chemical reactions with Cl⁻ and SO₄²⁻. These reactions transform previous hydration products into soft or expansive minerals, resulting in cracks, mass loss, and poor sample quality. To maintain good durability in the seawater, equal to or over 20% GGBS is recommended since the binders could bond the particles, making sample structures denser, thus more resistant to chemical attack.<br></p>