Background: Clay-basedand geosynthetic liners are generally used as hydraulic barrier in solid waste disposal facilities, mining tailing ponds, and soil-based wastewater treatment technologies, avoiding leaching of hazardous compounds to 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. Therefore, evaluate the best ratio for producing waste-based liners for civil engineering applications. Methods: The geotechnical characterization performing –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 rearranging 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 in 15%. Conclusion: The incorporation of WTS can improve or just do not interfere at 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.
Biomass ashes (BA) have been intensively studied as amendments for soil in earthworks. This paper aimed to geotechnically characterize BA from pines and olive trees compared to the soil from Castelo Branco, Portugal. Namely, granulometry, specific gravity, Atterberg limits and optimal compaction values were obtained and analyzed in order to valorize the residue incorporated into soils. This work is part of broader efforts to develop an alternative material that can be used in hydraulic barriers as liners and for soil reinforcement. Thus, BA can contribute to reductions in weight and plasticity, and filling properties. Further studies are needed, particularly mechanical and hydraulic performance tests. Keywords: biomass ashes, geotechnical and mechanical properties, residue valorization, soil reinforcement, liner material
Mineralogical and chemical evaluations are necessary to investigate the background and origins of materials. In terms of residues commonly produced around the world, ashes biomass stands out for its high calorific capacity and use for energy production at thermoelectrical facilities. Given current sustainability issues and new demands from society, ashes and soil from pine biomass in the Castelo Branco region were investigated to research possible anthropogenic contaminations, heavy metals among their composition, and their physic-chemical characteristics. These properties can be used to define possible valorisation methods through residue introduction into the soil for its reinforcement and liner application. The results indicated that ashes biomass could help achieve these objectives and could be introduced into the soil, due to its enrichment with pozzolanic minerals and fine granulometry, while having a low-density, which could reduce final weight; however it was considerably different from the original biomass, and contained anthropogenic contaminations and high concentrations of heavy metals. Keywords: biomass ashes, chemical and mineralogical properties, residue valorisation, soil reinforcement, liner material
A 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.
Direitos para esta edição cedidos à Atena Editora pelos autores. Open access publication by Atena Editora Todo o conteúdo deste livro está licenciado sob uma Licença de Atribuição Creative Commons. Atribuição-Não-Comercial-NãoDerivativos 4.0 Internacional (CC BY-NC-ND 4.0).
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