Supplementary material from "Synergistic Alkali Activation of Cement–C&DW Blends for Marine Dredged Clay Stabilization: Microstructural Evolution and Mechanical Performance"

The effects of alkali activators on the stabilization of marine dredged clay using Portland cement and construction and demolition waste (C&DW) have been systematically investigated. Firstly, single-factor tests revealed that sodium silicate (0-8.5%) increased 7-day unconfined compressive strength (UCS) by up to 119% through promoting the formation of calcium silicate hydrate (C–S–H) gel, whereas sodium hydroxide (1.5-2.5%) increased the UCS by up to 32.5%. calcium chloride demonstrated negative effects, decreasing UCS by 30% at a content of 2.0%.

Secondly, ANOVA results from the composite alkali activator tests indicated that SS exerted a statistically significant effect on UCS, particularly at lower moisture content where optimal formulation (8.5% SS, 2% SH, 0.5% CC with 10% Portland cement and 10% C&DW) achieved 926% UCS increase versus reference specimen. Finally, XRD and SEM analyses confirmed that SS plays a dominant role in strength development by promoting C-S-H gel polymerization via silicate ions, while SH sustains alkaline conditions for clay mineral dissolution, and CC regulates C-S-H crystallization.