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- Geotechnical Characterization of Water Treatment Sludge for Liner Material Production and Soft Soil ReinforcementPublication . Marchiori, Leonardo; Studart, André; Albuquerque, Antonio; Cavaleiro, Victor; Silva, AbilioA water treatment sludge (WTS) was characterized in order to evaluate if its properties would be suitable for use as liner of earthworks or for strengthening a clay soil. A WTS and a clayey soil was characterized in terms of granulometry, cumulative volumes, specific surface, density, plastic limit, liquid limit, water content, hydraulic conductivity, and characteristics of compaction (optimal water content and dry density). This study aimed to exhibit and evaluate these investigated parameters of WTS, soft soil and mixed proportions between the materials for liners’ material production while evaluating soft soils’ reinforcement feasibility. The results have shown WTS’s contribution with its fine granulometry and compaction characteristics, indicating filling properties and possible feasibility as soft soils additions for liners’ material production while being applicable for soils‘ reinforcements, corroborating with existing literature on the subject. Thus, the currently developed investigation has exposed WTS as a potential addition for these applications while also attending society’s new demands towards a more sustainable future.
- Environmental-chemical compatibility of granitic-mining waste for liner materialPublication . Marchiori, Leonardo; Studart, André; Morais, Maria Vitoria; Albuquerque, Antonio; Andrade Pais, Luís; Cavaleiro, VictorMining waste is generated from extracting mineral resources and, without proper disposal, can lead to negative environmental impacts because it can contain pollutants. Emerging studies of alternatives valorizing and reusing the residue through sustainable practices. Therefore, this research investigated the potential of granitic mining waste for waterproof liner materials, considering that most used liners, clays and geosynthetics, are increasingly scarce and costly solutions, respectively. This paper aims to analyze chemical compatibility, and microscopic structure of a granitic-mining mud to produce alternative material for liner construction. It was mixed in a clay at 25% and 50% ratio to develop a waste-based geocomposites. European limits for pollutants were respected for all mixtures, and the permeability remained less than 10-9m/s, which appears to be feasible for liners production. Thus, the valorization of mining waste as liner material arises as solution for creating new waste-based added-value product in the scope of circular economy.
- Mechanical and Chemical Behaviour of Water Treatment Sludge and Soft Soil Mixtures for Liner ProductionPublication . Marchiori, Leonardo; Studart, André; Albuquerque, Antonio; Andrade Pais, Luís; Boscov, Maria Eugenia Gimenez; Cavaleiro, VictorBackground: Clay-based and geosynthetic liners are generally used as hydraulic barriers in solid waste disposal facilities, mining tailing ponds, and soil-based wastewater treatment technologies, avoiding the leaching of hazardous compounds into subsoil and groundwater. Water treatment sludge (WTS) is a water treatment plant (WTP) residue which due to hydraulic properties seems to decrease the permeability in WTS:soil mixtures and may become an alternative material to produce sustainable waste-based liners. Objectives: This research aims to characterize and analyse physical, chemical and mechanical parameters of a WTS, a soft soil and four mixtures WTS:soil following 05:95%, 10:90%, 15:85%, 20:80% ratios, Thereby, evaluating the best ratio for producing waste-based liners for civil engineering applications. Methods: The geotechnical characterization was performed for particle size distribution, specific surface, specific gravity, Atterberg limits, and Normal Proctor compaction; chemical composition due to oxides analyses through X-ray fluorescence (XRF), mineralogical description by X-ray diffraction (XRD) and scanning electron microscope (SEM) with energy dispersive spectrometer (EDS) coupled for imaging; and mechanical behavior performing - –oedometric consolidation, consolidated undrained (CU) triaxial, and falling head permeability. Tests were conducted for all mixtures, the soil, and WTS, with pointed-out exceptions. Results and Discussion: The results showed that the fine-grained WTS filled the soil voids but rearranged soil particles, thus, compacted dry unit weight decreased with WTS addition, probably due to its chemical composition with high amounts of aluminium and silica. The compressibility of the compacted mixtures did not differ significantly compared to the soil, while the shear strength analysis demonstrated a reduction in cohesion and an increase in the effective internal friction angle proportional to WTS addition. Hydraulic conductivity increased with WTS until 10% of residue introduction, decreased for 15%, and continued to decrease for 20%, reaching optimum permeability at 15%. Conclusion: The incorporation of WTS can improve or just not interfere with soil’s properties to be used as liner material in solid wastes storage facilities, mining ponds and soil-based wastewater treatment technologies. Furthermore, 15% of WTS (15:85% mixture) incorporation provided the best results meeting the hydraulic conductivity requirement for liner materials, i.e., equal, or lower than 10-9 m/s. The reuse of WTS for this purpose would allow producing a new added-value material in the scope of circular economy.