Clay Stabilization Research Articles

Stabilization of Soft Clay with Sustainable Binders for Dry Deep Mixing Design

Abstract Dry deep mixing (DDM) is a soil stabilization method widely used in countries with large soft clay areas, such as in the Nordic countries. In Finland, DDM is performed using a binder material that commonly consists of cement and lime in a 50:50 or 30:70 ratio. However, both lime and cement generate large amounts of emissions of carbon dioxide, which has led to a shift toward alternative materials in recent years. This paper presents the results of an extensive testing program where samples of Finnish sensitive soft clay are stabilized with eight different low emissions binders and tested by means of the uniaxial compression strength test. The alternative binders comprise different by-products and/or pozzolanas in varied percentages, which include lime kiln dust (LKD), biomass-based fly ash from bioenergy production, gypsum, blast furnace slag, as well as lime and cement in reduced amounts. The tests were performed on samples stabilized at different binder densities (60, 70, 100, 120, 140, and 160 kg/m3) and after 28 days of curing to determine the optimum densities for DDM design purposes. The results showed that binders such as blast furnace cement, the cement- quicklime-gypsum (33:33:33), and the LKD-cement (50:50) exhibited higher strength than the traditional lime/cement binders at different binder densities. In addition to these results, a simplified CO2 emissions calculation procedure is proposed for a DDM design supporting a road embankment, and two different emissions factors are obtained for the investigated binders. The results showed that some alternative binders can provide high binding efficiency with low CO2 emissions.

Effects of construction waste clay bricks on growth of pepper and improvement of clay properties

Pot experiment, indoor detection and triaxial experiment were carried out to study the effects of construction waste clay bricks on the growth of pepper and improvement of clay nutrient and strength properties. The clay from southern Shaanxi was rolled and screened by 2mm, and the construction waste clay bricks were ground to 0-2, 2-5 and 5-7 mm. Construction waste with different particle sizes was mixed with clay in a mass ratio of 0:1 (CK), 1:1, 1:2, and 1:3. Construction waste accounted for 0, 50, 33 and 25% in the four mixed matrices, respectively. About 33~50% construction waste clay bricks with particle size of 5~7mm mixed with pure clay showed higher nutrient levels than that of pure clay. The plant height and yield of cultured pepper were the highest in construction waste clay bricks of 33~50%, with particle size of 5~7mm mixed with pure clay and the soil strength 33.2% higher than that of pure clay. This treatment provides sufficient nutrient conditions for plant growth. This not only provides sufficient nutrient conditions for pepper growth, but also meets the corresponding shear strength and suitability for clay area soil improvement, especially for clay slope stability improvement. The application value and prospect of using construction waste in land engineering construction and soil organic reconstruction and identified a new way of utilizing construction waste as a resource were explored. Bangladesh J. Bot. 52(2): 503-514, 2023 (June) Special

Effects of construction waste clay bricks on growth of pepper and improvement of clay properties

Pot experiment, indoor detection and triaxial experiment were carried out to study the effects of construction waste clay bricks on the growth of pepper and improvement of clay nutrient and strength properties. The clay from southern Shaanxi was rolled and screened by 2mm, and the construction waste clay bricks were ground to 0-2, 2-5 and 5-7 mm. Construction waste with different particle sizes was mixed with clay in a mass ratio of 0:1 (CK), 1:1, 1:2, and 1:3. Construction waste accounted for 0, 50, 33 and 25% in the four mixed matrices, respectively. About 33~50% construction waste clay bricks with particle size of 5~7mm mixed with pure clay showed higher nutrient levels than that of pure clay. The plant height and yield of cultured pepper were the highest in construction waste clay bricks of 33~50%, with particle size of 5~7mm mixed with pure clay and the soil strength 33.2% higher than that of pure clay. This treatment provides sufficient nutrient conditions for plant growth. This not only provides sufficient nutrient conditions for pepper growth, but also meets the corresponding shear strength and suitability for clay area soil improvement, especially for clay slope stability improvement. The application value and prospect of using construction waste in land engineering construction and soil organic reconstruction and identified a new way of utilizing construction waste as a resource were explored. Bangladesh J. Bot. 52(2): 503-514, 2023 (June) Special

Performance evaluation and stabilization mechanism of red clay treated with polyurethane

Red clay, a widely distributed soil, weakens significantly when exposed to water. This poses challenges for using it as a foundation for urban infrastructure, as rainwater scouring, infiltration, and external loads can cause uneven settlement and landslides, compromising structural integrity. To address this issue, we propose the use of a green highly permeable water-soluble polyurethane material (PSP) as an alternative to conventional curing agents. We conducted a series of tests to evaluate the efficacy of PSP in improving the mechanical properties of red clay. Acoustic emission tests were used to examine the failure mode of PSP-stabilized red clay, while scanning electron microscopy provided microscopic insights into clay stabilization mechanisms. The triaxial test results establish empirical relationships between strength, stiffness, toughness, and control parameters (PSP content, moisture content, and confining pressure) of the stabilized clay. We found that PSP-stabilized soils exhibit ductile failure and strain hardening, with PSP curing agents effectively enhancing clay strength and stiffness within a 3-day curing period. Univariate analysis reveals positive correlations between peak energy absorption values, peak stress rates, and PSP content, while showing a negative correlation with moisture content. Confining pressure variations have relatively little effect on peak stress ratios of PSP soils, and PSP soil stiffness minimally influences confining pressure as PSP content increases. Importantly, PSP treatment significantly increases ductility compared to untreated clay soils, distinguishing PSP soils from hydric soils.

On the use of one-part geopolymer activated by solid sodium silicate in soft clay stabilization

The application of geopolymers in ground improvement has garnered significant attention in recent years. However, most geopolymer preparations have focused on the two-part method, which not only has negative environmental impacts but also falls short of meeting practical requirements. This study aimed to address these limitations by employing solid sodium silicate (Na2O·nSiO2, n is the molar ratio, NS) to activate binary precursors (fly ash [FA] and ground granulated blast furnace slag [GGBFS]), along with water, to synthesize a one-part geopolymer (OPG) for soft clay stabilization. The primary factors on the properties of the OPG binder were firstly identified through macro- and micro-tests. Subsequently, the optimization of the OPG mixing proportion was achieved by reducing the molar concentration of NS, and was further used for soft clay stabilization. The effects of the FA/GGBFS ratio (0, 0.1, and 0.2), curing period (7, 14, and 28 days), and binder content (0.15, 0.20, and 0.25) on the mechanical properties of the OPG-stabilized soft clay were then evaluated using unconfined compressive strength (UCS) tests. Furthermore, mercury intrusion porosimetry (MIP), scanning electron microscopy with energy dispersive X-ray spectrometry (SEM-EDS), and X-ray diffraction (XRD) techniques were employed to examine the evolution of microstructure, hydrate composition, and mineral/phase of the OPG-stabilized soft clay samples. The experimental results indicated that an appropriate OPG stabilizer proportion was achieved with an FA/GGBFS ratio of 0.1, water/precursor ratio of 0.8, molar ratio of NS of 1.0, and molar concentration of 3 mol/L. The high-early-strength feature of OPG binder contributed to the rapid strength development of the stabilized soft clay at an early age. A noticeable pozzolanic reaction was observed in the OPG-stabilized soft clay sample with an FA/GGBFS ratio of 0.1. Additionally, a binder content of 0.20 was recommended for the stabilization of soft clay due to its optimal balance between economic benefits and meeting the required UCS criteria in soil stabilization. Finally, a reliable nonlinear relationship between UCS and porosity of OPG-stabilized soft clay was established to assess the mechanical properties and stabilization effects of the OPG-stabilized soft clay for practical applications. This study greatly enhances the scientific understanding of geopolymerization in the OPG system by using a combination of the binary precursor of FA and GGBFS and the solid NS activator. It sheds light on the stabilization mechanism of OPG-stabilized soft clay. The outcomes of this study make a valuable contribution to the advancement of environmentally friendly soil stabilizers, promoting green and low-carbon practices in the field of ground improvement.

Research on strength improvement and stabilization mechanism of organic polymer stabilizer for clay soil of subgrade

Soil stabilizer can improve the physical and chemical properties of clay and improve the bearing capacity of subgrade soil. A kind of liquid polymer soil stabilizer of vinyl acetate-ethylene was used in this paper. First of all, the effects of stabilizer content and curing time on the unconfined compressive strength (UCS) and the water stability were studied to clarify the strength evolution of stabilized soil. Furthermore, the pH test, Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDS), X-Ray Diffraction (XRD), and Fourier Transform Infrared Spectroscopy (FTIR) were performed to study mineralogy, morphology, and chemistry of clay minerals and polymer stabilizer, as well as the potential interaction of the both. The results show that the stabilized soil has a quick strength growth before 14d that reaches about 89% of the final strength, then followed by a decreasing growth rate. Extending the curing time and increasing stabilizer content contribute to the dense agglomeration structure and homogenous skeleton structure. When immersed in the water, the strength has the largest reduction amplitude within the first day. The pore-filling effect, physicochemical bonds, and surface wrapping for clay particles are dominating roles of the polymer stabilizer. The formed fine colloidal particles could fill micro-pores distributed in the matrix. In addition, the polar functional group of carbonyl could create a strong electrostatic attraction and hydrogen bond with the clay minerals, further improving the adhesion, while there are no other new function groups generated. The polymers containing hydrophobic groups are recommended in consideration of water stability.

Stabilisation of Soft Clay, Quick Clay and Peat by Industrial By-Products and Biochars

The stabilisation of soft soils using the traditional binders cement and quicklime are known to emit large amounts of carbon dioxide. To reduce this carbon footprint, substitutes such as industrial by-products have been thoroughly tested as viable alternatives for soil stabilisation. However, recent research has also shown that biochar from biomass pyrolysis can in some instances have a positive stabilisation effect and even result in a carbon-negative footprint. This paper presents a laboratory study to investigate the stabilisation effect of five industrial by-products and four types of biochar on three natural Norwegian soils: two clays with low and high water contents and one peat with a very high water content. The soils and binders were characterised by their mineralogical and chemical compositions. The biochars had varying stabilisation effects on the clays when combined with cement, with some negative stabilisation effects, whilst the effect was very beneficial in the peat, with a strength increase of up to 80%. The industrial by-products showed opposite results, with beneficial effects in the clays and a strength increase of up to 150%, but negative stabilisation effects in the peat. Correlating the mineralogical and chemical compositions to stabilisation effects was found to be challenging.

Study on Optimum Selection Method of Additives for Slick-Water Fracturing Fluid

In order to clarify the research idea of fluid system optimization in slick-water fracturing, a scientific and effective single-agent optimization method was selected to study the performance optimization method and performance evaluation method of drag reducer, clay stabilizer and cleanup additive in slick-water fracturing fluid. The specific experimental steps and application examples were investigated. To select the drag reducer, the drag reduction rate rate of the drag reducer at different concentrations should be measured first, the optimal concentration of a single agent should be selected, and then the stability test of temperature, flow rate and shear time should be performed on the optimal concentration of a single agent, and finally the combination formula with high drag reduction rate rate and stable performance can be selected. To optimize the clay stabilizer, the optimal concentration of single agent should be obtained by measuring the anti-swelling rate of different single agent and different concentration, and then the anti-swelling rate of each compound formula should be determined according to the optimal concentration of single agent, and finally the anti-swelling performance of the composite combination should be evaluated according to the core flow experiment. The optimal concentration of a single agent should first be optimized according to the surface tension of the cleanup additive, and then the combined formula should be optimized according to the surface tension of the combined combination, and the cleanup additive ability should be evaluated by core spontaneous imbibition or measuring the increase rate of cleanup additive.

Efek Penambahan Bahan Aditif Non-Alami terhadap Perilaku Lempung Plastisitas Tinggi yang Distabilisasi dengan Semen

Cement is proven increasing the strength of soft clays. Monmorillonite has a high shrinkage. Another hand, Kaolin has a small shrinkage. Waste material usage for stabilization agent was widely carried out this decade. BAFA (bottom ash fly ash) and POFA (palm oil fuel ash) are rich in Silica and Alumina, so they used to substitute of cement. The study examined the effect of Monmorillonite, Kaolin, BAFA and POFA on stabilization of clay with cement. Bentonite from 4% to 16% (is equated to BAFA and POFA, in ratio of 2:1) and Kaolin by 2.5%, used to reduce clay shrinkage, mixed with cement by 3% and 5%. Soil behavior will be reviewed from laboratory tests on curing-noncuring and soaked-unsoaked conditions. The results show changes in Atterberg Limits and Hydraulic Conductivity (permeability, k). Cement as well as BAFA and POFA reduce Plastic Limit greater than Liquid Limit. So, Plasticity Index decreased. It’s can be seen that cement and ash waste decreasing the permeability value. More Ash and less cement, make more impermeable soil. Addition of 3% and 5% cement increased the UCS values from 14.32 kPa to 81.20 kPa and 589.68 kPa and CBR value from 0.78% to 4.20% and 589.68 42.12% respectively

Determination of the efficiency of clay stabilizer component of fracturing fluid through coreflood experiments with terrigenous clay reservoir rock samples

Determination of the efficiency of clay stabilizer component of fracturing fluid through coreflood experiments with terrigenous clay reservoir rock samples

Exfoliating kaolin to ultrathin nanosheets with high aspect ratio and pore volume: A comparative study of three kaolin clays in China

A revised intercalation-assisted liquid exfoliation method is proposed to exfoliate three typical kaolin clays (Beihai, Longyan and Suzhou) in China. By combining intercalation, ball milling, ultrasound and freeze-drying technologies, the ultrathin kaolin nanosheets with large lamellar size (1–2 μm), low thickness (∼10 nm), high aspect ratio (∼130) and large pore volume (∼0.3 cm3/g) were obtained. A large number of kaolinite monolayer structures were observed in AFM images, indicating high exfoliation efficiency. The morphology, crystal structure and microstructures of kaolin samples during the intercalation and exfoliation processes are studied in detail by high resolution XRD, SEM, BET and AFM analysis. The mechanism for effective intercalation, exfoliation and stabilization of kaolin clays is clarified. The ultrathin kaolinite nanosheets slightly curved after exfoliation process were found to form some porous structures between the kaolin nanolayers, providing plenty of interlayer spacing for functional loading or interfacial binding. These ultrathin kaolin nanosheets might have the advantages to improve the adhesion ability, loading capacity, and mechanical properties of kaolin-based composite materials.

Stabilization of Soft Clays Exposed to Freeze–Thaw Cycles Using Chitosan

Stabilization of Soft Clays Exposed to Freeze–Thaw Cycles Using Chitosan

Sustainable utilization of chemically depolymerized polyethylene terephthalate (PET) waste to enhance sand-bentonite clay liners

Polyethene terephthalate (PET) waste poses major environmental harm which can be minimized by reusing it in clay soil stabilization. In general, various polymers are known to reduce hydraulic conductivity and increase the shear strength of clays. However, the application of the effect of a chemically depolymerized form of PET, i.e., Bis (2-Hydroxyethyl) terephthalate (BHET) has not been performed as an additive in Compacted Clay Liners (CCLs) for landfills. This research focuses on the effect of the air curing period (1 and 28 days) on the hydromechanical behavior of BHET-treated SBM (0, 1, 2, 3, and 4 % by dry weight). Results from One Dimensional Consolidation tests showed that an increase in BHET content reduced both compressibility and hydraulic conductivity of SBM due to pore clogging mechanism of swollen BHET hydrogel, however, hydraulic conductivity reduced over 28 days of curing due to loss in re-swelling availability of the hydrogel, thereby allowing less tortuous paths to flow. Results from Consolidated-Drained Direct Shear tests showed that for 1 and 28-days curing, BHET treatment to SBM increased the cohesion (c’) due to strong polymer interparticle bridging, however, polymer coating over the sand grains causes a reduction in its surface roughness to decrease the frictional angle (ϕ'). SEM (Scanning Electron Microscopy) and EDX (Energy-dispersive X-ray spectroscopy) analysis on BHET-treated specimens support the flocculation of bentonite, polymer bridging of sand and clay-sand polymer links. A significant Pb2+ removal capacity was also observed with BHET-treated SBM from the batch tests. FTIR (Fourier Transform Infrared Spectroscopy) analysis on batch sorption specimens confirms the role of the carbonyl groups (C = O) and hydroxyl groups (OH) present in the BHET structure indicating the possibility to adsorb Pb2+. The findings of the study suggested that a mechanism of interaction exists between sand-bentonite and BHET polymer and it can be adopted in CCLs design.

Determining technological properties of drilling muds

Purpose. To rationalize well washing by considering the influence of the annular channel limitation, granulometric composition of the mud, limitation of the joint movement of mud particles, drill string rotation, shape of the movement channel, and rheological properties of a cleaning agent. Methodology. Applied laboratory studies on the properties of drilling fluids are carried out using modern methods of analytical analysis and experimental studies, in particular, by using general principles of mathematical and physical modelling, methods of processing the results of studies in the EXCEL, MATNSAD environment, control and measuring devices of the laboratory of washing liquids of the Department of Oil-and-Gas Engineering and Drilling of Dnipro University of Technology (hydrometer, viscometer, plastometer, stalagmometer), and materials (technical water, clay bentonite powder, reagents, stabilizers and activators, surfactants as well as equipment and laboratory base of “Ukrnafta” PJSC to carry out certain stages of research. Findings. The properties of surface-active substances and activated washing liquids are analyzed. The main technological properties of drilling fluids are studied. Comprehensive information on the physical and chemical ability of flushing drilling fluids is provided. The main technological measures ensuring the stability of drilling process using activated-surfactant drilling fluids are considered in detail. The main technological principles of determining rational formulations of a selected cleaning agent in the circulation of Newtonian liquids are formulated and substantiated. A detailed description of surfactants, their properties and methods to study the formed solutions is given. Originality. The process of a rock-breaking tool on the well bottom will be stable in the conditions of dynamic equilibrium of the rock-breaking processes and removal of broken products into the annular space. Therefore, for a correct understanding of wellbore washing issues, basic regularities are established of the specified processes and the influence of various factors on these processes. Practical value. It has been proven that in order to give a drilling fluid the necessary properties that, on the one hand, will ensure an increase in the efficiency of rock breaking on the well bottom, and, on the other hand, will create favourable conditions for stable removal of cuttings onto the surface and maintenance of the well walls in a stable condition, it is necessary to apply different methods, in particular chemical activation as well as magnetic, thermal and electrochemical activation, in its different varieties.

Assessment of sustainable expanded glass granules for enhancing shallow soil stabilization and dynamic behaviour of clay through resonant column tests

In geotechnical engineering applications such as artificial slope fills, backfill for retaining walls and embankments are required to be as light as possible, yet more durable and provide drainage. Recently, the use of waste materials in stabilization applications is preferred due to both a more sustainable environment and economic advantages. In this study, expanded glass granules, used in lightweight and stabilization material such as autoclaved aerated concrete, were mixed with clay at various ratios (by mass 1 – 2% and by volume 2.5 – 5 – 7.5 – 10 – 15%) and their dynamic properties such as initial shear modulus, damping ratio and modulus reduction were investigated under various effective pressures comparatively using resonant column/torsional shear test (RCTS). Considering the shear modulus results of the mixtures by mass (1–2%) and by volume (2.5–5 − 7.5%), it is observed that low and medium shear strain amplitude (0.001–0.05%) were observed to be higher in the range of up to 40% and 10% compared to the reference sample. In addition, it was calculated that the density of the mixed specimens (2.5–5 − 7.5%) with high shear modulus were up to 6.2% lower than the reference sample. The study concludes that the use of expanded glass granules (by mass 1–2%, by volume 2.5, 5%) is experimentally satisfactory for shallow soil stabilization in geotechnical applications where the presented boundary conditions are valid.

A Novel Ascorbic Acid Based Natural Deep Eutectic Solvent as a Drilling Mud Additive for Shale Stabilization

During drilling, almost 70% of wellbore instability issues result from the encountering of shale formations. Various additives such as salts, silicates, and polymers are used in water-based mud to enhance its shale-inhibition capability; however, such additives have certain limitations. Lately, ionic liquids and deep eutectic solvents (DES) have been used by various research groups as shale inhibitors in drilling fluid due to their biodegradability and efficacy. However, their popularity faded when a natural derivative of DES, i.e., Natural Deep Eutectic solvent (NADES), came into the picture. This research utilizes the in-house-prepared Ascorbic acid and Glycerine (AA:Gly)-based NADES as a drilling fluid additive for shale inhibition and compares its efficacy with counterpart inhibitors such as KCl, imidazolium-based ionic liquid, and Choline Chloride-based DES. The results show that 3% NADES improved the overall Yield point to Plastic viscosity ratio, with a 39.69% decline in mud cake thickness and a 28% decline in the filtrate volume of drilling mud. Along with improved drilling fluid properties, 3% NADES resulted in 77.77% shale inhibition and 87% shale recovery. Surface tension, d-spacing, zeta potential, and FESEM have been conducted to justify and elucidate the inherent mechanism behind the working of NADES as a drilling fluid additive and clay stabilizer. Thus, Ascorbic acid-based NADES is recommended as a potential non-toxic and cheap drilling fluid additive to improve drilling fluid properties and clay stability.

Structure liming reduces draught requirement on clay soil

Liming with ‘structure lime’, comprising approximately 80–85% ground limestone and 15–20% slaked lime, has been promoted in subsidised environmental schemes in Sweden since 2010 to increase clay aggregate stability and mitigate particulate phosphorus losses to surface waters. To date, approximately 65,000 ha have been structure-limed. Apart from stabilising aggregates, liming may also improve other physical properties, such as soil strength. This study examined the effect of increasing application rate (0–16 t ha-1) of structure lime on soil strength, approximated by horizontal (draught requirement) and vertical (penetrometer resistance) measurements, in eight field soils (clay content 26–38%) to which structure lime had been applied two, three, four or six years previously. Draught requirement when cultivating with a multipurpose cultivator significantly decreased (by 11%) with the highest application rate of structure lime (16 t ha-1) compared with an unlimed control. This reduced the wheel power requirement by 7.1 kW and diesel consumption by 1.2–1.4 L ha-1, and lowered CO2 emissions by 3–4 kg ha-1. To clarify the general effect of structure liming, the mean value of all limed treatments was compared with that of the unlimed control. This showed that structure liming in general significantly reduced the draught requirement (by 7%). However, penetrometer resistance measurements revealed no significant effects of structure liming and no relation between draught requirement and penetrometer resistance measurements. Overall, the results indicate that structure liming can reduce fuel consumption, due to easier soil tillage, and thus lower CO2 emissions.

Rheological studies of high-density fracturing fluid using high-density brine and carboxymethyl hydroxypropyl guar (CMHPG) for high-temperature well condition

This work investigated carboxymethyl hydroxypropyl guar (CMHPG) as a potential base polymer for a fracturing fluid used in deep tight gas wells, synonym to high-temperature reservoirs. Fracturing is a common method to improve oil production by creating fractures in potentially productive reservoirs using fracturing fluids. Fracturing fluids are typically composed of water, sand, proppant, and many different additives to alter the capabilities of the fluid.A stable high-density fracturing fluid (HDFF) was developed to cope with scorching good temperatures up to 350F (177C)as well as to reduce the surface treating pressure. The HDFF consists of NaBr heavy brine, CMHPG, clay stabilizers, and zirconium and borate crosslinkers. A linear gel fluid was prepared by combining NaBr brine with CMHPG before adding the additives. The resulting fluid was then tested using a high-pressure, high-temperature (HPHT) rheometer.The results showed that the performance of the HDFF was optimum in an alkaline environment between pH 10 to 12. The efficiency of zirconium and borate crosslinkers were optimum at 0.7 ppm and 1.5 ppt, respectively. Concentrations higher than these values are not only uneconomical but will cause the fluid to be overly crosslinked, consequently reducing efficiency. In actual field operation, this is disastrous when the fluid does not flow to the fracturing column but instead swirls around the drill string as the drill string rotates. On the other hand, a reduction of concentration below the optimum values can cause fluid instability at high temperature reservoirs.The study was limited to using two different kinds of crosslinkers and various concentrations. Future studies can be conducted using other kinds of crosslinkers, as well as an investigation into the effects of varying temperatures, pressures, and pH on the HDFF using CMHPG.It can be concluded that HDFF using CMHPG as the base polymer can be a potential use in formulating fracturing fluids.Information on the rheological behaviour of HDFF using NaBr and CMHPG can provide a reference point for future scientists in developing a new formulation of fracturing fluid.

Effect of sugarcane bagasse ash and plantain leaf ash on geotechnical properties of clay soil from Efab Estate, Awka, Anambra State

This study investigated the feasibility of using agricultural wastes: sugarcane bagasse ash and plantain leaves ash for clay soil stabilization. The sample was mixed using five trial mixes: 0%BA:10%PLA, 3%BA:7%PLA, 5%BA:5%PLA, 7%BA :3%PLA, 10%BA:0%PLA and a control mix. Characterization of these ashes was done using the X-ray fluorescence testing method. Specific gravity, sieve analysis, Atterberg limits, compaction and California bearing ratio tests were also assessed. The clay soil was described as A-7-6 (AASHTO). After X-ray characterization, BA and PLA possessed 61.97% and 28.27% pozzolanic content respectively. From the liquid limit results, on addition of 3%BA :7%PLA, a significant decrease in values of 47.0%, 32.0% and 15.0% to 36.0%, 26.0% and 10.0% for LL, PL and PI was documented. Also, the addition of plantain leaves alone significantly decreases atterberg limit values. For compaction, 3%BA and 7%PLA recorded the least MDD value of 18.44kN/ m3 and peak value of 19.42kN/m3 at 0%BA: 10%PLA. 10%PLA and 10%BA recorded CBR soaked values of 57.8% and 62.1% whilst 7%BA:3%PLA yielded best results of 51.3% CBR soaked values. These findings reveal significant improvements in strength and index properties of the clay soil. In conclusion, bagasse ash and plantain leaves ash produce an eco-friendly stabilizer that can be utilized as subbase material in the stabilization of clay soils

Hybrid process of adsorption and electrochemically based green regeneration of bentonite clay for ofloxacin and ciprofloxacin removal.

Removal of emerging contaminants, such as antibiotics, from wastewater by adsorption is a simple, low-cost, and high-performance process; however, regeneration and reuse of the exhausted adsorbent are necessary to make the process economically viable. This study aimed to investigate the possibility of electrochemical-based regeneration of clay-type materials. For this, the calcined Verde-lodo (CVL) clay was saturated with the antibiotics ofloxacin (OFL) and ciprofloxacin (CIP) in one-component systems by an adsorption process and then subjected to photo-assisted electrochemical oxidation (0.45 A, 0.05 mol/L NaCl, UV-254 nm, and 60 min), which promotes both pollutant degradation and adsorbent regeneration. The external surface of the CVL clay was investigated by X-ray photoelectron spectroscopy before and after the adsorption process. The influence of regeneration time was evaluated for the CVL clay/OFL and CVL clay/CIP systems, and the results demonstrate high regeneration efficiencies after 1 h of photo-assisted electrochemical oxidation. Clay stability during regeneration was investigated by four successive cycles in different aqueous matrices (ultrapure water, synthetic urine, and river water). The results indicated that the CVL clay is relatively stable under the photo-assisted electrochemical regeneration process. Furthermore, CVL clay was able to remove antibiotics even in the presence of natural interfering agents. The hybrid adsorption/oxidation process applied here demonstrated the electrochemical-based regeneration potential of CVL clay for the treatment of emerging contaminants, since it can be operated quickly (1h of treatment) and with lower consumption of energy (3.93 kWh kg-1) than the traditional method of thermal regeneration (10 kWh kg-1).