Treated Soil Samples Research Articles

Study on the Effect of Magnesium Chloride-Modified Straw Waste Biochar on Acidic Soil Properties.

Soil biochar is a kind of organic matter rich in carbon, which is of great significance in soil fertility improvement, fertilizer type innovation and greenhouse gas emission reduction. In this paper, Mg-modified biochar was prepared by thermal cracking using rice straw and corn straw as raw materials. The Mg-modified biochar and unmodified biochar were fully mixed with prepared soil samples at the addition amounts of 0.5% (w/w), 1% (w/w) and 2% (w/w), respectively, and then simulated indoor soil cultivation experiments were carried out. The effects of magnesium ion-modified biochar and non-modified biochar on soil chemical properties and the effects of different amounts of biochar on soil properties were studied. The results showed that the yield of Mg-modified biochar from rice straw and corn straw, prepared by pyrolysis, was 65%, and the ash content was large. The pH of MG-modified corn stalk biochar (MCBC) is weakly basic (8.55), while the pH of MG-modified rice stalk biochar (MRBC) is basic (10.1), and their internal structures are slightly different. After the application of biochar prepared from rice straw and maize stover, soil indicators were determined. Compared to the control, the chemical properties of the treated soil samples were significantly improved, with an increase in soil pH, an increase in the content of effective nutrients, such as fast-acting potassium, fast-acting phosphorus and alkaline dissolved nitrogen, and an increase in the content of the total phosphorus and total nitrogen, as well as an increase in the content of organic matter. The Mg-modified biochar was generally superior to the unmodified biochar in improving soil fertility, at the same addition level. It was also found that the rice-straw biochar performed better than the corn-stover biochar and had a more obvious effect on soil improvement in terms of fast-acting potassium, ammonium nitrogen, nitrate nitrogen, total phosphorus and total nitrogen contents.

Predictive models for treated clayey soils using waste powdered glass and expanded polystyrene beads using regression analysis and artificial neural network

Waste materials contribute to a wide range of environmental and economic problems. To minimize their effects, a safe strategy for reducing such negative impact is required. Recycling and reusing waste materials have proved to be effective measures in this respect. In this study, an eco-friendly treatment is investigated based on using waste powdered glass (WGP) and EPS beads (EPSb) as mechanical and chemical admixers in soils. For this purpose, Atterberg limit, standard proctor, free swell, and unconfined compression tests are performed on soil samples with different ratios of waste materials at their optimum moisture contents. The obtained test results indicate that adding WGP to cohesive soils increases the unconfined compressive strength (UCS) and reduces free swell (FS). In contrast, using EPSb reduces both FS and UCS of the treated soil samples. An optimum combination of both waste materials is determined for the improvement of the properties of high plasticity clay used in this study. Furthermore, multiple linear regression (MLR) and artificial neural network (ANN) methods are used to predict the FS and UCS of the clayey soils based on the data obtained here and the experimental test results reported in the literature. Once the FS and UCS values of untreated soil and additive percentages are defined as independent variables, both methods are shown to predict the FS and UCS values of the treated soil samples on a satisfactory level with the coefficient of correlation (R2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${R}^{2}$$\\end{document}) values greater than 0.926. Additionally, when only the index properties (liquid limit, plastic limit, and plasticity index) of the soil samples with waste materials are used as dependent variables, the R2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${R}^{2}$$\\end{document} values obtained by the ANN method are 0.968 and 0.974 for FS and UCS, respectively. The results of the untreated soil samples' FS and UCS tests are known, and the linear regression and ANN techniques yield similar results. Lastly, the ANN method is used to predict the FS and UCS of the treated samples in accordance to the limited predictors (e.g., only the Atterberg limits of the soil sample).

Modified diatomite for soil remediation and its implications for heavy metal absorption in Calendula officinalis

BackgroundAmong different adsorbents, natural and inorganic compounds such as diatomite are important and advantageous in terms of high efficiency and cost-effectiveness, and function in stabilizing heavy metals in the environment. Calendula officinalis, a plant known as a high accumulator of heavy metals, was cultivated in soil treated with varying concentrations of modified diatomite to demonstrate the efficiency of modified diatomite in stabilizating of heavy metals in soils,ResultsThe modification of diatomite aimed to enhance Calendula officinalis adsorptive properties, particularly towards heavy metals such as lead (Pb), Zinc (Zn), Chromium (Cr), Nickle (Ni), and Copper (Cu), common contaminants in industrial soils. The experimental design included both control and treated soil samples, with assessments at regular intervals. Modified diatomite significantly decreased the bioaccumulation of heavy metals in contaminated soils except Zn, evidenced by decreased DTPA extractable heavy metals in soil and also heavy metal concentrations in plant tissues. Using 10% modified diatomite decreased 91% Pb and Cu, 78% Cr, and 79% Ni concentration of plants compared to the control treatment. The highest concentration of Zn in plant tissue was observed in 2.5% modified diatomite treatment. Remarkably, the application of modified diatomite also appeared to improve the nutrient profile of the soil, leading to enhanced uptake of key nutrients like phosphorus (P) 1.18%, and potassium (K) 79.6% in shoots and 82.3% in roots in Calendula officinalis. Consequently, treated plants exhibited improved growth characteristics, including shoots and roots height of 16.98% and 12.8% respectively, and shoots fresh and dry weight of 48.5% and 50.2% respectively., compared to those in untreated, contaminated soil.ConclusionThe findings suggest promising implications for using such amendments in ecological restoration and sustainable agriculture, particularly in areas impacted by industrial pollution.

Assessing the impact of immobilisation on the bioavailability of PFAS to plants in contaminated Australian soils

Per- and polyfluoroalkyl substances (PFAS) have become a key concern to both environmental and human health due to their extreme persistence in the environment and their ability to bioaccumulate in plants, animals, and humans. In this mesocosm study, Australian PFAS-contaminated soil with a mean total concentration of 8.05 mg/kg and a mean combined PFHxS + PFOS concentration of 7.89 mg/kg was treated with an immobilisation sorbent (RemBind®) at different application rates (0.5, 1, 1.5, 2, 3, 4, and 5% w/w). To assess the efficacy of this immobilisation treatment, PFAS leachability, PFAS plant uptake, and ecotoxicity tests were conducted. Leachability testing was performed according to the Australian Standard Leaching Procedure (ASLP) at pH 5 and 7. A grass species (Dactylis glomerata) was used to measure plant uptake of PFAS from untreated and treated contaminated soil. In addition, the Microtox test was used to assess the associated ecotoxicity. The immobilisation treatment resulted in a significant reduction of 88.5–99.8% in the total PFAS leachability and 88.7–99.8% in the combined PFOS and PFHxS leachability at pH 5. Similarly, significant reductions (5–12-fold) were observed in the plant uptake of total PFAS and combined PFOS and PFHxS in all treated soil samples. In addition, although the Microtox test showed relatively low ecotoxicity in all the experimental samples, including the untreated soil, a significant decrease in the ecotoxicity of treated soil samples was observed. The results from this study highlight that this treatment approach has the potential to reduce both PFAS leachability and plant bioavailability with a relatively low associated ecotoxicity. This is likely to reduce the risk of the transfer of PFAS into higher trophic levels. This immobilisation treatment may, therefore, reduce the risk associated with PFAS-contaminated soils and may be an important remediation tool for managing certain PFAS-contaminated soils.Graphical

The Unconfined Compressive Strength of Hy-drated Lime Stabilized Clayey Soil at Different Water Contents and Different Curing Times

This research was done to find out how adding hydrated lime and extra water content to clayey soil samples affecting their unconfined compressive strength (UCS). The clayey soil is a locally available soil from the clayey soil area in Cyrene, northeastern of Libya. In the soil samples, hydrated lime (HL) was added at a rate of 5% of the dry weight of the soil. The standard compaction test was conducted on the untreated natural soil sample “NS” so that the optimum water content at the maximum dry density can be determined wop1. Because of the addition of hydrated lime to the soil will affect the dry density-water content relationship, the standard compaction test was conducted again on the treated soil sample “NS+5%HL” to determine another optimum water content wop2. These optimum water values {wop1 =17.8 & wop2=19.5} will be used to prepare unconfined compressive strength specimens. In the experimental work two soil mixtures will be used beside the natural soil mixture. The first mixture "NS+5%HL+wop1" and the second mixture "NS+5%HL+wop2" were prepared in addition to the natural soil mixture "NS+wop1". All unconfined compressive strength specimens for the first and second mixtures were extracted and tested at 7 and 14 days of curing, then comparison were made. The first mixture, "NS+5%HL+wop1" will be compared with the natural soil mixture, "NS+ wop1" in order to understand the impact of HL addition. The effect of the water content changing can be seen when the second mixture, "NS+5%HL+wop2" is compared with the first mixture, NS+5%HL+wop1. According to the findings, Although the first mixture’s specimens have the least dry density value, the UCS values increased by 218.5 and 386.5% at 7 and 14 days of curing, respectively, when compared to the natural soil mixture. This illustrates the result of the added hydrated lime. At curing times of 7 and 14 days, respectively, the UCS values for the second mixture fell by 8.61 and 14.11% when compared to the first mixture. And this illustrates the impact of variations in water content.

Psychrophiles to control ice-water phase changes in frost-susceptible soils

The phase changes of soil water or porous media have a crucial influence on the performance of natural and man-made infrastructures in cold regions. While various methods have been explored to address the impacts of frost-action arising from these phase changes, conventional approaches often rely on chemicals, mechanical techniques, and the reuse of waste materials, which often exhibit certain limitations and environmental concerns. In contrast, certain organisms produce ice-binding proteins (IBPs) or antifreeze proteins (AFPs) to adapt to low temperatures, which can inhibit ice crystal growth by lowering the freezing point and preventing ice crystallization without the need for external intervention. This study explores the potential of three psychrophilic microbes: Sporosarcina psychrophile, Sporosarcina globispora, and Polaromonas hydrogenivorans, to induce non-equilibrium freezing point depression and thermal hysteresis in order to control ice lens growth in frost-susceptible soils. We hypothesize that the AFPs produced by psychrophiles will alter the phase changes of porous media in frost-susceptible soils. The growth profiles of the microbes, the concentration of released proteins in the extracellular solution, and the thermal properties of the protein-mixed soils are monitored at an interval of three days. The controlled soil showed a freezing point of − 4.59 °C and thermal hysteresis of 4.62 °C, whereas protein-treated soil showed a maximum freezing point depression of − 8.54 °C and thermal hysteresis of 7.71 °C. Interestingly, except for the controlled sample, all the protein-treated soil samples were thawed at a negative temperature (minimum recorded at − 0.85 °C). Further analysis showed that the treated soils compared to porous media mixed soil freeze (1.25 °C vs. 0.51 °C) and thaw (2.75 °C vs. 1.72 °C) at extensive temperature gap. This freezing and thawing temperature gap is the temperature difference between the beginning of ice core formation and completed frozen, and the beginning of ice core thawing and completed thawed for the treated soil samples selected from different incubation days. Overall, this study presents a novel bio-mediated approach using psychrophilic microbes to control ice formation in frost-susceptible soils.

Bioremediation of Engine Oil-Contaminated Soil using Selected Indigenous Moulds

The polycyclic aromatic hydrocarbons (PAHs) utilizing the potential of moulds from engine oil-polluted soils were assessed. These PAHs are known to be toxic, mutagenic and carcinogenic in the environment. Consequently, the study aims to evaluate the potential of indigenous moulds from engine oil in the remediation of contaminated soil. Samples were collected from engine oil-polluted soils from Samonda, Ibadan, Oyo State Nigeria. The ability of four potential indigenous moulds to degrade the PAH fraction of the engine oil-polluted soil sample was assessed using the gas chromatography technique. Four moulds were identified based on their cultural and microscopic characteristics and were confirmed as Aspergillus flavus, Aspergillus parasiticus, Aspergillus oryzae and Aspergillus nidulans. The highest biodegradation potential was observed in treated soil sample containing Aspergillus flavus (55.15%) followed by Aspergillus parasiticus (55.00%), Aspergillus oryzae (44.51%) and the least biodegradation potential was observed in the sample containing Aspergillus nidulans (24.16%) after 60 days of treatment. This study revealed that indigenous mould has the ability to utilize toxic fractions of petroleum products as their sole carbon sources therefore are the major bio-remediating agents in the sampling area.

Influence of anionic polyacrylamide on the freeze–thaw resistance of silty clay

Freeze–thaw (FT) alternation can severely affect the properties of fine–grained soils, often leading to the failure of foundation backfill projects, such as open canals and roads in cold regions. To address these problems, a water–soluble anionic polyacrylamide (APAM) was used to improve the properties of fine–grained soils, particularly silty clay. This study aims to analyze the effects of the APAM polymer on the physico–mechanical and microstructural properties of silty clay under both unfrozen and FT cycles. For this purpose, different addition dosages and FT cycle numbers were determined, and then a series of zeta potential, thermal conductivity, permeability, triaxial compression, and scanning electron microscopy (SEM) tests were conducted on the soil samples. Additionally, a unidirectional freezing test was constructed to investigate the coupled thermo–hydro–mechanical processes of APAM–treated soil samples under subzero temperature conditions. The results showed that the addition of the APAM polymer significantly enhanced the macroscopic engineering properties and microstructural characteristics of silty clay. This improvement was attributed to the charge neutralization, adsorption bridging effect, and hydrophobic interaction provided by the APAM polymer. However, all the soil samples showed a significant deterioration in their engineering properties during FT cycles, especially after the third FT cycle. It was notable that APAM–treated soil samples were superior to the untreated sample in terms of FT resistance. During the unidirectional freezing process, the pore water migrated from the unfrozen zone towards the freezing front due to the temperature gradient. The treated sample's pore water migration volume was considerably lower than that of the untreated sample, resulting in a 55.25% reduction in total frost heave when the APAM dosage was 0.30%. The findings of this paper may be utilized to mitigate the risk of frost damage to foundation backfill projects in cold regions, as well as to get a better understanding of the stabilization mechanism of the eco–friendly APAM polymer.

Dynamic Shear Responses of Combined Contaminated Soil Treated with Nano Zero-Valent Iron (nZVI) under Controlled Moisture

Nano zero-valent iron (nZVI) technologies have gained recognition for the remediation of heavily contaminated sites and reused as backfilling soil. The moisture environment at these sites not only impacts the reactions and reactivity of nZVI but also the dynamic responses of compacted backfilled soils. The research explored the effects of different nZVI dosages (0.2%, 0.5%, 1%, 2%, and 5%) on Lead-Zinc-Nickel ions contaminated soil under a controlled-moisture condition. Cyclic triaxial tests were performed to evaluate the dynamic responses of treated soil samples prepared using a consistent moisture compaction method. Particle size distribution and Atterberg limits tests assessed changes in particle size and plasticity. The study revealed a minor reduction in the particle size, liquid limit, plastic limit, and plasticity index of the contaminated soil. Notably, increasing nZVI dosages in treated soils led to growing Atterberg limits. An increase in the specific sand fraction of treated soils was observed with nZVI, suggesting nanoparticles–soil aggregations favoring existing larger particles. Stepwise loading cyclic triaxial tests indicated an optimal dynamic response of soil treated with 1% nZVI under the controlled-moisture condition, proven by notable enhancements in the maximum shear modulus, maximum shear stress, less shear strain, and higher damping ratio within the small strain range. It should be noted that moisture content in treated soils declined significantly with higher nZVI dosages during preparation, potentially impeding effective aggregation and the formation of a solid soil skeleton. These findings advance the importance of considering the balanced nZVI dosage and moisture content when employing the safety assessment of practical applications in both nano-remediation techniques and soil mechanics.

Effects of metakaolin and sodium silicate treatment on highwater content dredged clay for improved construction fill performance

This study experimentally investigated the strength characteristics of metakaolin (MK) and sodium silicate (SS) treated dredged clay at high water content for use as construction fills. A series of laboratory tests including direct shear tests, unconfined compression tests, SEM and XRD tests were carried out to systematically evaluate the effects of water content, sodium silicate modulus, curing agent content, and curing time on the strength behavior of MK and SS treated dredged clay samples. The direct shear test results showed that the shear strength at a given vertical stress consistently increases with the increase of curing agent content and curing time while decreasing with the modulus of SS. Both cohesion and friction angle increase with increasing curing agent content and curing time, while reducing with the increasing modulus of SS. Unconfined compression test results showed that all samples tested exhibit a strain-softening behavior. The value of unconfined compressive strength increases with the increase of curing agent content and curing time but decreases with the increase of water content and modulus of SS. The optimal dosage combination is a sodium silicate modulus of 0.9, curing agent content of 12%, and curing time of 28d. SEM test confirmed the formation of gels in the treated soil sample, the dredged clay showed a more uniform and denser microstructure after treatment. Through XRD analysis, it is not easy to generate direct chemical reactions with no new mineral components generated in the sample. For high-water content dredged clay, it is recommended to use an optimum dosage combination of MK and SS to achieve a better treatment effect for use as construction fills.

Strength characteristics of marine clay mixed with coal ash and cement with microstructural verification

This study uses coal ash obtained from the Tanjung Bin coal power plant consisting of a mixture of fly ash and bottom ash at different ratios. Such mixtures will be used with the minimum amount of Ordinary Portland Cement to stabilise marine clay. Compaction data corresponding to a mixture of coal ash and OPC mixed with marine clay soil provides 1535 and 1600 kg/ m 3 MDD and 18–22.2% OMC ranges, as additive percentages are increased. The unconfined compressive strength test indicated the highest increase at 50BA:50FA ratio with a value of 536 kPa at 15% of additive. The strength of the treated soil sample would also increase with increasing additive percentage and curing period. The XRD of untreated soil sample indicates composition intensity for minerals like quartz, mica, kaolinite, calcite, montmorillonite, and muscovite generally decreased with curing time; on the other hand, halloysite composition reduced. However, a new mineral is formed: calcium aluminium silicate hydroxide hydrate. Moreover, the FESEM results show that the treated marine clay surface particles looked denser with time. Structural voids were also reduced. In line with the XRD and FESEM test outcomes, the EDX results indicated that the formed cementitious products comprised calcium aluminate silicate hydrate.

Degradation, altered microbial community composition, and protein expression in bacterial consortium/fungus inoculated crude oil contaminated loamy soil

Accidental discharge of crude oil due to rupturing of old oil pipelines and blasts in oil refineries leads to contamination of agricultural land/adjacent areas and changes in microbial community and protein expression in the contaminated soil. Our previous study identified a bacterial consortium (Bacillus amyloliquefaciens MW532755+ Pseudomonas sp. MW444887) and a fungus (Aspergillus sydowii KY614299) with crude oil degrading ability. These microorganisms were used in the present investigation to degrade total petroleum hydrocarbon in naturally contaminated loamy soil (25% w/w) collected from the Assam region of India. The half-life of crude oil in uninoculated (T1), bacterial consortium (T2), and fungus-inoculated (T3) soils were 135.9, 47.5, and 58.2 days, respectively. The bacterial consortium and the fungus treatments altered the soil bacterial community and metabolic pathways, evidently from the analyses using metagenomics and predicted functional proteomics. The sequencing analysis using Ion Torrent showed the presence of 287 genera in the oil-polluted and treated soil samples. At the Genus level, abundances of Pseudomonas and Bacilli were observed, and the reads representing those of the Domain Bacteria for uninoculated (T1), bacterial consortium (T2), and fungus (T3) treated soils were 214525, 584054 and 489423, respectively. The predicted functional proteomics analysis for the protein-regulating genes, functional pathways, and protein families showed the presence of diversified pathways responsible for higher metabolic activities (q < 0.05). The quantitative polymerase chain reaction (qPCR) analysis showed that, compared to fungus treatment, bacterial consortium increased the abundance of 16S rRNA gene copies of Archaea, Alphaproteobacteria, and Bacteroidetes and also the gene copies of nitrogen cycling such as nifH (106 to 108) were highest, followed by nirK (104 to 108), amoA (104 to 105), and nirS (104 to 106)The present study suggested that the bacterial consortium as the hydrocarbon degraders was better than fungus and can be used in the future for oil remediation purposes.

Response of High Swelling Montmorillonite Clays with Aqueous Polymer

Expansive clays containing mineral montmorillonite exhibit swelling and shrinkage due to variations in the moisture content, leading to significant distresses. There has been a growing interest in chemical and polymer additives treated for high swelling montmorillonite clays in recent years. However, limited attention has been paid to the effect of polyacrylamide on the soil’s swelling behavior. Moreover, nontraditional methods of the soil treatment are applied for the rapid stabilization of soil. In this article, polyacrylamide polymer is used as an additive to expansive clays to control the swelling phenomenon. Three different percentages—2.5%, 5%, and 7.5%—of polymer are blended with oven-dried soil to determine Atterberg limits, compaction features, and swelling characteristics. Additionally, electrical impedance measurement is conducted on treated soil samples with different moisture contents. The electrical resistance of soils and polymer-treated soils is measured based on the electrical resistivity correlation of soils. Tests results for soils stabilized with polyacrylamide show that swelling is significantly reduced with increasing the additive content. Moreover, the addition of polymer improves resistivity of soil. Aqueous polyacrylamide can be utilized as an effective stabilization additive to enhance properties of expansive clays.

Effect of Grain Size Distribution of Soil on Immobilization of Cadmium and Nickel in Contaminated Soil Using Nano Zerovalent Iron: A Factorial Design and Response Surface Methodology Approach

Urban soils get contaminated due to the unscientific disposal of industrial effluents and solid waste, contaminating the soil with heavy metals. Contaminated soils need to be remediated to avoid the ingestion of toxic heavy metals. The immobilization of heavy metals is one of the methods to remediate contaminated soils. The primary purpose of this study was to explore the effect of grain size distribution (GSD) of soil on the efficiency of immobilization of toxic heavy metals in soil when nano zerovalent iron (nZVI) is used to immobilize the metals. Preliminary studies conducted with the 23 factorial design method confirmed that GSD is a significant factor along with the level of contamination and nZVI dosage in the immobilization of heavy metals in soil. Experiments were conducted with cadmium (Cd) and nickel (Ni), the toxic heavy metals, and three soils with different finer particles than 75 µm. Immobilization efficiency was obtained by comparing the leachability of contaminated and treated soil samples using the toxicity characteristic leaching procedure. Reduction in available fraction and variation in the speciation of heavy metals was observed through the sequential extraction procedure. The response surface methodology was adopted for analysis with three levels of GSD, contamination, and nZVI dosage. For Cd, a reduced cubic model was the best fit with a coefficient of determination (R-square) of 0.93, and for Ni, a quadratic model was the best fit with an R-square of 0.92. Both these models were validated experimentally. The efficiency variation followed an optimum curve concerning GSD, contamination level, and the nZVI dosage. For multimetal contamination, the immobilization efficiency gradually decreased from 10% finer to 90% finer soil, both in the case of Cd and Ni. It was observed that for both single metal and multimetal contamination, the interaction between soil and the nZVI plays a vital role in immobilization along with the factors considered.

Comparison on the Behaviour of Bamboo and Polypropylene Fibre in Soil Stabilization

Abstract: In the practice of geotechnical engineering, soil improvement is regarded as one of the most significant solutions, particularly in the case of weak soil conditions. Expansive soil exposed to climatic changes and moisture content, experiences a significant volume shift. Building foundations, paving structures, irrigation systems, and other geotechnical engineering projects are just a few examples. To prevent swelling and shrinkage characteristics, stabilizing the expansive soil is crucial. For considerations of sustainability and economy, stabilizing material selection is crucial. In this project, the soil stabilization is accomplished using reasonably priced and easily accessible materials like bamboo fiber and polypropylene fibre. Soil is replaced by NaOH treated bamboo fibre from 0.2 to 1% at the interval of 0.2% and the same is repeated by replacing the soil with 1% to 3% at the interval of 0.5%. It was observed that, there is marginal increase in dry density of the treated soil samples and reduction compressibility. The maximum Unconfined Compressive Strength (UCS) was obtained for optimum 0.4% of bamboo fibre and 1.5% of polypropylene fibre with replacement of soil. The performance of bamboo fibre was compared with that of polypropylene fibre. The bamboo fibre showed better results than polypropylene fibre.

Using a blend of cement and waste glass powder to improve the properties of clayey soil

Adopting an appropriate soil stabilization technique is necessary since weak soil can lead to foundation instability and reduce a structure's life. Selecting the appropriate admixtures is very frequent among the various soil stabilization methods. This study scrutinized the feasibility of employing a blend of cement and waste glass powder (WGP) to improve the properties of clayey soil, which was classified as clay with intermediate plasticity according to the Indian Standard Soil Classification System (ISSCS). Using WGP in soil stabilization is a promising way to prevent its disposal in landfills, which may pose a severe environmental threat. In addition, using WGP can reduce the need for conventional binders like lime and cement. As a result, reducing carbon emissions will lead to sustainable development. For this purpose, crushed waste glass from waste glass production was used. A blend of 5% fixed proportion of cement and 2.5, 5, 7.5, and 10% of WGP was mixed with the soil sample. Atterberg limits, Proctor's compaction, and California bearing ratio (CBR.) tests were executed on untreated and treated soil samples. According to the test results, incorporating a blend of cement and WGP in clayey soil reduced its liquid limit and plasticity index. The plasticity index of the soil sample was decreased by 50% when a blend of 5% cement and 5% WGP was added to the soil sample. In other words, as per the ISSCS, clay with intermediate plasticity (CI) was changed to clay with low plasticity (CL) after using a combination of 5% cement and 5% WGP. Maximum dry density increased, whereas optimum moisture content decreased as the soil sample was modified using a cement blend and WGP. After adding 5% cement and 10% WGP, the maximum dry density of the soil sample was increased by 6%, and the optimum moisture content was reduced by 3%. The improvement in CBR. was significant after the soil treatment with a blend of cement and WGP. The CBR. of the treated soil was increased by 260% when a combination of 5% cement and 5% WGP was used.

Influence of Wetting-Drying Cycles on Strength Behaviour of Cured Lime Treated Soil Contaminated with Monovalent and Divalent Sulphatic Solutions

Exposure of lime treated expansive soil to sulphatic compounds are known to develop distresses due to the formation of ettringite or thaumasite, causing excess swell and alteration in strength behaviour. However, effect of wetting–drying (W-D) cycles caused due to seasonal variations on the behavior of lime treated soil exposed to sulphate contamination has not been addressed properly. Hence, present work investigates the impact of varying W-D cycles (0–4) on unconfined compressive strength (UCS) behaviour of lime treated soil in presence of two different sulphatic [i.e., monovalent sodium sulphate (Na2SO4) and divalent gypsum (CaSO4·2H2O)] contaminations. Lime treated soil samples are, firstly, cured for 7, 14 and 28 days and then used for further process of W-D cycles after completion of each curing periods. Varying sulphate concentrations (i.e., 3000, 10000, 16000, 20,000 and 30000 ppm) as prepared by using Na2SO4 and CaSO4·2H2O using distilled water have been used as contaminating solutions in W-D cycles process for lime treated soil. Strength behaviour of samples subjected to W-D cycles are determined at both wet and dry sides of each cycle. The results revealed that strength of lime treated soil is influenced highly by sulphatic concentration, types of sulphatic compound (monovalent or, divalent cations), curing periods as well as number of W-D cycles. Adverse impacts on strength are pronounced with an increase in sulphate concentration and number of W-D cycles. However, significant adverse effect on strength and durability are pronounced in the samples subjected to sulphate concentration more than 16000 ppm. Further, study is extended to elucidate the experimental results with physicochemical behaviour and microanalyses [XRD, FESEM, EDAX, FTIR and TGA-DTA]. It is confirmed that progression of number of W-D cycles with the increase in sulphatic concentration has influenced significantly to the microstructure of lime treated soil.

Enhancement of Clay Compressibility and Strength Using Nano Magnesium Oxide

In order to satisfy the requirements of environmentally friendly construction projects and minimize greenhouse gas emissions, it was necessary to focus on utilizing nanomaterials instead of conventional materials to enhance clay soils; nano Magnesium Oxide was suggested for this study. The compression and unconfined compressive strength tests were achieved to assess the compressibility behavior and strength of silty clay treated using nano magnesium oxide. Additionally, an investigation into the alteration of the clay microstructure was conducted using field emission scanning electron microscopy (FE-SEM) tests. The silty clay utilized in this research is characterized by a compression index 0.23 and an undrained shear strength of 53 kPa. The soil was treated by adding different percentages of nano-MgO (0.4%, 0.5%, 0.6%, and 0.8%), and the curing period was seven days. The treated soil samples were prepared based on the optimal water content and maximal dry density of the natural soil. The results indicate that utilization of nano Magnesium Oxide leads to a reduction in both values of the index of compression (Cc) and recompression index (Cr), in addition to a decrease in the value of the coefficient of compressibility (av). Also, the test finding for unconfined compressive strength demonstrates a noticeable increase in strength as the percentage of nano-MgO increases, accompanied by a reduction in failure strain. Adding 0.6% (the optimum percentage) of nano Magnesium oxide enhances the strength by about 114% and decreases the value of the compression index by about 36% compared with natural soil.

Improving Engineering Properties of Soil for Highways Purposes by Halloysite Nanotubes

This study investigates the stabilizing effects of Halloysite nanotubes on the geotechnical features of gypseous soil as a subgrade. The soil that was utilized for this study was collected from Ayn al-Tamr in Karbala City, southwest of Iraq, having an average gypsum of 30% and was designated as (SP) by (USCS). As a percentage of the dry unit weight of the soil, the gypseous soil was mixed with a small amount of nanomaterial (Halloysite nanotubes). A set of physical and chemical identification tests have been conducted on the original soil, as well as additive, direct shear, collapsibility, and California bearing ratio (CBR) testing on both untreated and treated soil samples using Halloysite nanotubes. Three different additive proportions (2.5, 5, and 7.5) % by dry unit weight of soil were added to soil samples. The results of the conducted tests revealed that the geotechnical properties of the soil sample were considerably modified. As the amount of utilized nanomaterials increases, the collapse potential instantly decreases. In addition, soil strength and stability were increased by increasing CBR values, and the collapse severity was changed from moderate trouble to no problem. Thus, the value of 2.5% of Halloysite nanotubes can be considered as an optimum percentage based on the results of the mentioned tests.

Consolidated Drained Triaxial Test on Treated Coastal Soil and Finite Element Analysis Using PLAXIS 2D

Coastal areas are susceptible to erosion and accretion; therefore, coastal soil mechanical properties and ability to withstand loads are important factors to consider. Coastal erosion is inevitable as the sand and silt particles move inexorably from place to place. This study investigates the primary consolidation behaviour of treated coastal soil by comparing the empirical data obtained from triaxial tests based on analytical calculations and FEM software, PLAXIS 2D. The aim is to propose an optimum mixture to improve coastal soil’s geotechnical properties, especially in shear strength and stiffness. Two different material models, including lime/RHA and cement/RHA, were utilized to compare the performance of advanced constitutive treated soil samples against the Mohr–Coulomb material model. 8% lime and rice husk ash (portions of 1 : 2) were chosen to be replaced with cement, as an application of waste material can reduce the cost and environmental impact. All the triaxial tests were conducted at effective confining pressures of 50 kPa, 100 kPa, and 200 kPa. While using PLAXIS 2D, the asymmetrical condition for modelling the triaxial test and 15 nodded triangular elements, as well as the Mohr–Coulomb model for soil properties, are used to simulate the empirical data to verify this study’s effectiveness. The modelling of 2-dimensional drain behaviour involves setting out the model geometry and boundary conditions. The results revealed that the deviatoric stress and volumetric changes of LRHA increased in a range of 4.5 to 5.2% and 72.18 to 141.79%, respectively, as compared to CRHA. The FE analysis results for peak deviator stress values reasonably agree with the experimental results. The variation was in the range of 1.22% to 4.10%. Eventually, the treated soil’s peak and maximum shear strengths are reported to allow flexible use in future projects.