Effects of rates of consolidation on low-carbon solidification of marine deposits with recycled ISSA and GGBS

The solidification of dredged marine sediments with high water content is important for maintenance dredging and reclamations. To reduce the carbon emission of solidification, low-carbon recycled wastes such as incinerated sewage sludge ash (ISSA) and ground granulated blast-furnace slag (GGBS) have been recently adopted as binding materials to replace conventional Portland cement. For soil slurry with ultra-high water content, using the consolidation-solidification combined method is an effective way to reduce the volume and improve the final mechanical properties. However, it is unclear how the consolidation interacts with solidification using the binding materials. In this study, a series of laboratory tests were conducted on dredged Hong Kong marine deposit slurry mixed with ISSA and GGBS with alkali activation by lime. The elemental consolidation tests controlled with different constant rates of strain and multistage loadings demonstrate that the rate of consolidation has significant effects on volume reduction and yielding stress development during consolidation-solidification treatment. Consolidation-solidification achieves higher volume reduction and yielding stress than pure solidification. As the rate of consolidation decreases, there is a smaller volume reduction at the same effective stress and less yielding stress enhancement at the same curing time. A scanning electron microscope with energy dispersive spectrometer was used to investigate hydration products and soil fabric after treatment. The slower rate of consolidation causes the looser structure and finer needle-shaped products with the same curing period, which can explain the mechanical properties observed from the element tests. • A pilot study on rate effects in consolidation-solidification of dredged sediments • Sustainable binders from recycled wastes were used for solidifications • Strain rates significantly affect the cementation and volume reduction • Microstructures in treated slurry were affected by rates of consolidation