Hydraulic Barrier Material Research Articles

Utilization of organoclay amended bentonite for hydraulic barrier applications under adverse electrolyte environment

Inorganic ions such as sodium and calcium are often found in industrial leachates, municipal solid waste leachates and deep geological repositories, which can significantly impact the geotechnical properties of hydraulic barrier materials. Researchers have suggested the utilization of organoclays as landfill liner amendments, especially when the liner is in contact with organic contaminants. This study focuses on the impact of inorganic salts (NaCl and CaCl2) on the geotechnical properties, such as consistency limits, swelling, and hydraulic conductivity of organoclay-amended bentonite (BOC) liners. Different concentrations of salt solutions (0, 0.1 N and 1 N) were selected for the execution of Atterberg limits, free swell tests, and oedometer tests. The surface charge characteristics of bentonite and organoclay were attained with the aid of zeta potential measurements. The variation in the surface topographies of soil samples at different electrolyte conditions was analyzed with the help of scanning electron microscope images. The addition of organoclays significantly reduced bentonite's swelling characteristics and liquid limit due to the unique hydrophobic and organophilic attributes of organoclay but increased the hydraulic conductivity. However, the influence of inorganic salts on the geotechnical parameters of organoclay-amended bentonites showed less variance than that of bentonite. Also, no soil samples exceeded the limiting hydraulic conductivity criteria required for landfill liners, i.e. 1 × 10−9 m/s. Hence, organoclay-amended bentonites could potentially be utilized for hydraulic barrier applications even in an electrolytic environment without compromising the hydraulic conductivity criteria.

Hydraulic conductivity of compacted manufactured sand tailings–bentonite mixtures: a new hydraulic barrier material

Hydraulic conductivity of compacted manufactured sand tailings–bentonite mixtures: a new hydraulic barrier material

Saturated hydraulic conductivity of compacted steel slag-bentonite mixtures——A potential hydraulic barrier material of landfill cover

The feasibility of using steel slag and bentonite mixtures to construct the hydraulic barrier of a landfill cover was explored in the present study. Fine-grained steel slag (SS; particle diameter < 1 mm) and sodium-activated calcium bentonite (SACB) were used to prepare compacted specimens, and the saturated hydraulic conductivity (ks) was measured using a flexible-wall permeameter. Influential factors including SACB content (BC), SS gradation, water-washing treatment of SS and compaction water content (ωcomp) were investigated. The hydraulic conductivity results were interpreted in microscopic scale through mercury intrusion porosimetry (MIP) and scanning electron microscope (SEM). It was found that when BC was below 10%, the ks value of the specimens prepared with well graded SS was about one order of magnitude lower than that of the specimens prepared with poorly graded SS. This was due to less macropores caused by better SS gradation. Yet, the effects of SS gradation on ks diminished as BC further increased to 15%, suggesting the dominant role of BC on ks at high BC. Water-washing treatment of SS helped reduce ks significantly to 1.2 × 10−10 m/s at BC of 10%, owing to less multivalent cations and hence lower osmotic swelling reduction caused by cations. Controlling ωcomp 1–2% wetter than the optimum water content (ωopt) also helped reduce ks significantly, owing to the reduction of macropores. Accordingly, it is suggested to use well-graded SS mixed with 10% SACB and then compact at ωcomp slightly wetter than ωopt to the degree of compaction greater than 90% in engineering practice.

Development of expansive soil geopolymer binders for use in waste containment facility

Waste containment facilities require liners and covers for safe waste disposal, which can be efficiently achieved using robust green technologies. In the present study, a systematic approach was adopted towards the development of reliable expansive soil geopolymers suitable for waste containment application. Various factors that influence geopolymerisation were considered including the precursor type (PT), precursor content, liquid alkali hydroxide type (LT), activator-to-precursor ratio (A/P) and method of preparation. Multiresponse optimisation for permeability, volumetric shrinkage and unconfined compressive strength was executed to achieve soil geopolymers that satisfy the regulatory requirement as hydraulic barrier materials. This was done using a robust experimental design and the utility concept to prescribe a framework for achieving reliable soil geopolymers. The results obtained show that significant interactions between the factors (PT × LT) and (PT × A/P) affected the response characteristics and consequently the soil geopolymer performance. The aptness of the multiresponse optimisation was confirmed at 95% confidence interval, which revealed that the developed soil geopolymers can be used in waste containment facility under certain conditions. Evidence of the geopolymerisation process was clarified using microstructural analyses. Scanning electron microscopy and energy-dispersive spectroscopy supported the formation of N–A–S–H and K–A–S–H gels. Moreover, diffraction patterns for new minerals such as muscovite and crystobalite were formed, with the disappearance of clay minerals. The presence of aluminosilicate gel binding systems was revealed by Fourier transform infrared spectroscopy. The participation of clay minerals in the geopolymerisation distinguishes the developed expansive soil geopolymer from the conventional geopolymers developed for concrete applications.

Interaction of Landfill Leachate with Compacted Lateritic Soil Treated with Bacillus coagulans Using Microbial-Induced Calcite Precipitation Approach

AbstractThe performance of lateritic soil treated with Bacillus coagulans (B. Coagulans) was assessed for use as hydraulic barrier material in municipal solid waste (MSW) containment use. The soil ...

GEOTECHNICAL ASSESSMENT OF PALM OIL FUEL ASH (POFA) MIXED WITH GRANITE RESIDUAL SOIL FOR HYDRAULIC BARRIER PURPOSES

This paper assesses the geotechnical properties of granite residual soil treated with palm oil fuel ash (POFA), a waste from the palm oil factory for the purposes of hydraulic barrier in landfills. Granite residual soil treated with up to 40% palm oil fuel ash (by dry weight of the soil) was compacted using standard proctor compactive effort at the optimum moisture content. Index properties, hydraulic conductivity (k), volumetric shrinkage strain (VSS) and unconfined compressive strength (UCS) tests were carried out. Results showed that the index properties of samples met the minimum requirement for it to be used ass a liner. The maximum dry density and optimum moisture content decreased and increased respectively. The influence of POFA treatment on the geotechnical properties generally showed an improvement with up to 15% POFA which gave the acceptable results with regards to its usability as a hydraulic barrier material in landfill.

Strength characteristics of cemented sand–bentonite mixtures with fiber and metakaolin additions

ABSTRACTCompacted sand–bentonite mixtures have been used as a good alternative hydraulic barrier material to compacted clays. This study presents the results of a laboratory investigation on the strength characteristics of cement-stabilized sand–bentonite (CSB) mixtures and the effects of adding small amounts of fibers and metakaolin to the mixture material for strength improvement. The strength characteristics of the mixture materials were examined using unconfined compressive strength (UCS) tests and splitting tensile strength (STS) tests, with emphasis on evaluating the effects of different proportions of bentonite, fibers, and metakaolin within the CSB mixtures with a constant value of cement content. The test results indicated that the maximum improvements in UCS and STS were all attained in the CSB mixture with 10% bentonite content, and the inclusion of fibers and metakaolin of 1% each within the same CSB mixture led to an increase in UCS of about 40 and 70%, respectively. The addition of fibers also increased the ductility of the mixture material and was more effective for the improvement of tensile strength compared to that of metakaolin. The contribution of metakaolin to early-age strength (i.e., 3 and 7 days) of CSB mixture was found to be small due to the relatively low cement content in the mixture.

The Influence of Compactive Effort on Compacted Lateritic Soil Treated with Cement Kiln Dust as Hydraulic Barrier Material

The paper evaluates the suitability of lateritic soil treated with up to 10 % cement kiln dust (CKD) by dry weight of soil for the construction of waste containment facilities compacted at three energy levels. Laboratory tests were carried out on specimens prepared at molding water contents −2, 0, +2 and +4 % of the optimum moisture content and compacted with British standard light, West African standard or ‘Intermediate’ and British standard heavy (BSH) energies. Index, hydraulic conductivity, volumetric shrinkage and unconfined compression tests were carried out. Results obtained show improvement in index properties with CKD treatment. Regulatory criteria of maximum hydraulic conductivity value of 1 × 10−9 m/s, minimum unconfined compressive strength of 200 kN/m2 and maximum volumetric shrinkage strain (VSS) of 4 % were satisfied with a minimum 7.5 % CKD treatment when specimens were compacted at BSH energy level. The overall acceptable zone for the treated soil was achieved with 10 % CKD treatment for specimens prepared at molding water content range of 13.5–21.3 % and compacted with BSH energy.

The Use of Compacted Tropical Clay Treated With Rice Husk Ash as a Suitable Hydraulic Barrier Material in Waste Containment Applications

Protection of our environment from pollutants emanating from wastes generated by man made activities and disposal systems in less developed countries is now a matter of growing concern. Laboratory tests were conducted on compacted tropical clay treated with up to 16 % rice husk ash (RHA) an agro-industrial waste to access its suitability in waste containment barrier application. Soil–RHA mixtures was compacted using standard Proctor, West African Standard and modified Proctor efforts at −2, 0, 2 and 4 % of optimum moisture content. Index properties, volumetric shrinkage, hydraulic conductivity, and unconfined compressive strength tests were performed. Overall acceptable zones under which the material was suitable (low hydraulic conductivity 200 kN/m2) were obtained. Results suggest the suitability of this material in waste containment barrier application for up to 8 % RHA treatment,which will ameliorate the environmental problems created by this agro-industrial waste.

Compacted black cotton soil treated with cement kiln dust as hydraulic barrier material

Compacted black cotton soil treated with cement kiln dust as hydraulic barrier material

Paper Sludge Layer as Low Permeability Barrier on Waste Landfills

The use of paper sludge as a hydraulic barrier material in landfills is a technology that has gained some attention since the early 1990s and is an innovative way to recycle paper mill residuals. The geotechnical properties of paper sludge are similar to those of compacted clays. A laboratory test has been performed to evaluate the suitability of Slovenian waste paper sludge as landfill covering or sealing material. The sludges obtained from Slovene paper mills were examined for their geomechanical, chemical and sealing properties, as well as for their microbiological stability. The results of preliminary geotechnical studies of paper sludges indicate the expected relatively low strength properties (14 kPa < σ c < 81 kPa), high compressibility and a low coefficient of permeability 5.0* 10−10 < k < 7.8* 10−11. The pH values of the eluates are within the permissible limits 6.6–7.0. The strength properties of paper sludges and various composites of paper sludge can be improved by additives (fly ash, bentonite, cement) and various composites of different types of paper sludges. We improved the strength properties (273 kPa < σ c < 1064 kPa) of these paper sludges, but the coefficient of permeability k also increased slightly. This paper also aims to evaluate the suitability of paper mill sludge collected from various Slovene paper mills for use as hydraulic barrier in landfill covers.

Assessment of Some Hydraulic Properties of Slime Slurries from Sand Mining Pits Using a Modified Triaxial Cell

The generation of massive volume of slimes from sand mining industry ascertains the need for effective waste treatment. The application of slimes in landfill barrier construction works has been identified as one of the processes that can be used to reduce their volume, enabling in this way the rehabilitation of dangerous sites. This article presents a modified triaxial cell specially built to investigate high water content soils and discusses the results obtained from the investigation of the hydraulic properties of two slimes. The results of laboratory filter cake tests show that the slimes have reasonably good sealing capacities due to the formation of a cake layer on other porous materials upon draining. A relatively low hydraulic conductivity (1.5–3 × 10−9 m/s) was achieved, once the cake layer was formed. This is close to the prescribed 1 × 10−9 m/s required by the local environmental governmental authority for a landfill hydraulic barrier material, indicating their potential suitability as landfill barrier.

A case study of waste management at the Northern Finnish pulp and paper mill complex of Stora Enso Veitsiluoto Mills

This work presents the current waste management system at the pulp and paper mill complex of Stora Enso Oyj Veitsiluoto Mills at Kemi, Northern Finland. This paper covers examples of case studies carried out at the mill and describes how the wastes and by-products are utilized as a neutralizing agent for acidic wastewaters (i.e., green liquor dregs from the causticizing process), as a hardener in filling mine cavities (i.e., ash from the fluidized bed boiler), as a landscaping agent (i.e., ash as well as the fibre clay from chemical wastewater treatment plant), as a hydraulic barrier material for landfills (i.e., fibre clay), and as a soil enrichment agent (i.e., calcium carbonate from the precipitated calcium carbonate plant). In addition, the wood waste from the wood-handling plant, sawmill, packaging pallet plant and from the groundwood mill, as well as the biosludge from the biological wastewater treatment plant, are all incinerated in the fluidized bed boiler for energy production. Due to effective utilization of the solid wastes generated at the mills, the annual amount of waste to be disposed of in the landfill has decreased between 1994 and 2004 from 42,990 to 6083 tonn (expressed as wet weight). The paper also gives an overview of the relevant European Union legislation on the forest industry and on waste management, as well as of the pulping process and of the generation of major solid wastes in the pulp and paper mills.

Foundry Green Sands as Hydraulic Barriers: Field Study

A field study was conducted to determine if the field hydraulic conductivity of barrier layers constructed with foundry green sand is comparable to the hydraulic conductivity measured in the laboratory on laboratory-compacted specimens normally used for testing during design. Three test pads were constructed with foundry green sand. Their field hydraulic conductivity was measured using sealed double ring infiltrometers, two-stage borehole permeameters, and on large block specimens. Additional field hydraulic conductivity tests were conducted on the test pads after exposure to winter weather causing freeze-thaw cycling and summer weather causing desiccation. The field hydraulic conductivity data followed the same trends with bentonite content and liquid limit observed in the laboratory. When the bentonite content is greater than 6% (by weight), the plasticity index is greater than 3, or the liquid limit is greater than 20, the hydraulic conductivity is less than 10\U-7\N cm/s. Testing after winter exposure showed that the field hydraulic conductivity was unaffected by winter weather, even though the test pads underwent up to six freeze-thaw cycles (depending on depth). Similarly, exposing the test pads to summer weather had no measurable effect on the field hydraulic conductivity. The field study validated that foundry sand is a useful industrial by-product that can be beneficially used as a hydraulic barrier material.

Foundry Green Sands as Hydraulic Barriers: Laboratory Study

A laboratory testing program was conducted to assess the use of foundry sands from gray iron foundries, typically called green sands, as hydraulic barrier materials. Foundry green sands are mixtures of fine uniform sand, bentonite, and other additives. Specimens of foundry sand were compacted in the laboratory at a variety of water contents and compactive efforts and then permeated in rigid-wall and flexible-wall permeameters to define relationships between hydraulic conductivity, compaction water content, and dry unit weight. Additional tests were conducted to assess how hydraulic conductivity of compacted foundry sand is affected by environmental stresses such as desiccation, freeze-thaw, and chemical permeation. Results of the tests show that the hydraulic conductivity of foundry sand is sensitive to the same variables that affect hydraulic conductivity of compacted clays (i.e., compaction water content, and compactive effort). However, hydraulic conductivities <10−7 cm/s can be obtained for many foundry sands using a broad range of water contents and compactive efforts, including water contents dry of optimum and at lower compactive effort. The hydraulic conductivity of foundry sand was generally unaffected by freeze-thaw, desiccation, or permeation with 0.1 N salt solution or municipal solid waste leachate, but was incompatible with acetic acid (pH = 3.5). Hydraulic conductivity of foundry sands correlates well with bentonite content and liquid limit, with hydraulic conductivity less than 10−7 cm/s being achieved for bentonite content ≥6% and/or liquid limit >20.