This study investigates the sustainable use of seabed dredged sediments and water treatment sludges as construction materials using combined dewatering and cement stabilization techniques. Dredged sediments and water treatment sludges, typically considered waste, were evaluated for their suitability in construction through a series of dewatering and stabilization processes. Dewatering significantly reduced the initial moisture content, while cement stabilization improved the mechanical properties, including strength and stiffness. The unconfined compressive strength (UCS), shear modulus, and microstructural changes were evaluated using various analytical techniques, including unconfined compression testing, free-free resonance testing, X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX). The results show a direct correlation between reduced w/c ratios and increased UCS, confirming the potential of treated sludge as a subbase layer for roads and landfill liners. A chemical analysis revealed the formation of calcium silicate hydrate (CSH) and ettringite, which are critical for strength enhancement. This approach not only mitigates the environmental issues associated with sludge disposal but also supports sustainable construction practices by reusing waste materials. This study concludes that cement-stabilized dredged sediments and water treatment sludges provide an environmentally friendly and effective alternative for use in civil engineering projects.

Damage to the soil environment caused by petroleum hydrocarbon pollution has become increasingly evident. However, the chemical adsorption reaction between petroleum hydrocarbon pollutants and medium particles in unsaturated soil at actual sites remains unclear. To explore the reaction process and mechanism, a series of unsaturated experiments under sterile conditions were performed to simulate the soil state of site with n-hexadecane as a characteristic pollutant. Soil samples were collected regularly, and environmental factors, including oxidation-reduction potential (ORP) and pH, were monitored online. Through microscopic characterization and qualitative and semi-quantitative analysis methods, the morphological changes in medium particles before and after reaction were systematically analyzed. The characteristics of reaction products were determined using gas chromatography-mass spectrometry. The results showed that the consumption of oxygen (O2) and production of hexadecanoic acid [CH3(CH2)14COOH] were fundamental reasons for the decrease of ORP and pH. A hydroxyl radical (& sdot;OH) in medium particles might extract a methyl hydrogen (H) atom from n-hexadecane and turn it into an alkyl radical. The alkyl radical might eventually be oxidized by O2 in soil to 1-hexadecanol and CH3(CH2)14COOH. This study systematically explains the chemical adsorption reactions and mechanisms of petroleum hydrocarbon pollutants in unsaturated soils. In addition, it provides a theoretical basis for revealing the migration and transformation mechanisms of petroleum hydrocarbon pollutants in soil under hydrological conditions such as rainfall and water level fluctuations.