Untreated Soil Samples Research Articles

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).

Effect of Ground Nut Shell Powder on Soil Stabilization By IJISRT

Various varieties of soil may be found across the world. The engineering features of soil are the most significant consideration in any building development. Construction on expanding soil is the most essential difficulty that civil engineers encounter. The expansive soil has typically undesired engineering properties, such as poor shear strength, plasticity, and compressibility; it expands when wet and shrinks when dry. Its characteristics can be enhanced with appropriate stabilizing procedures. Black cotton covers around 15% of the soil in India. Crops produced on black cotton soil include pea nuts, cotton, wheat, jowar, linseed, tobacco, castor, sunflower, and millets. In comparison, the peanut industry generates millions of tons of garbage. Nowadays, a key issue is "How to benefit from the industrial waste product." Soil stabilization is performed in order to improve the engineering qualities of the soil. The rising expense of typical stabilizing chemicals, along with the need to economically utilize industrial and agricultural waste for positive engineering reasons, prompted an inquiry into the stabilizing potential of groundnut shell powder (GSP) in expansive soil. This study looks at how to improve the geotechnical characteristics of expansive soil by performing various tests such as specific gravity, atterberg limit, compaction test, and California bearing ratio test to determine the properties of the untreated soil sample and then adding 5%, 7%, and 9% ground nut shell powder by weight of soil. In this phase, only untreated soil testing are conducted. After receiving treated and untreated soil results, compare the untreated black cotton soil results to various percentages of ground nut shell powder results to determine the optimum amount of ground nut shell powder necessary to increase the stability of black cotton soil.

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.

The effect of SH-lime composite material on capillary water rise resistance in the Great Wall

Capillary rise of water leads to salt migration and accumulation, which is the main cause of erosion at the bottom of the Great Wall in Northwest China. In this study, we evaluated the effectiveness of SH (modified polyvinyl alcohol) and lime composite material against capillary water rise. We conducted comparative capillary rise cycle tests on two sample types: untreated Great Wall soil and soil treated with the SH-lime composite, using solutions of NaCl and Na2SO4 of specified concentrations. The surface hardness, strength, water-salt distribution, and pore size distribution of the samples were also evaluated. The results showed that: in the salt solution capillary rise cycle, the untreated soil samples quickly changed color and precipitated white crystals. As the test proceeded, the untreated soil samples developed cracks, followed by fragmentation at the corners, and finally collapsed. In contrast, the SH-lime solidified soil had less white crystal precipitation and no visible cracks after 7 cycles. This indicates that the overall integrity of the SH-lime solidified soil was higher. The capillary rise cycles also changed the pore size distribution of the samples. NaCl crystals tended to occupy and expand micropores and small pores, while Na2SO4 crystals tended to grow in large pores. In addition, Na2SO4 was more destructive to soil than NaCl. The SH-lime composite material reduced porosity and strengthened soil structure, which slowed down the expansion of large pores. The study concludes that SH-lime effectively inhibits capillary rise-induced water-salt migration and associated damage, making it a suitable choice for repairing capillary rise-prone Great Wall sites.

Cement Stabilization of soft soil subgrade and Cost Analysis

The soft soil when present in subgrade creates a lot of problem in highways. Due to soft soil subgrade, the rutting is predominant cause of flexible pavement failure all around the world. This kind of soil is either replaced or modified prior to construction of other layers of road to minimize the formation of rut. This study deals with stabilization of soft soil subgrade by cement. The sample was collected from a depth around existing road subgrade. A series of laboratory tests on untreated soil sample was first done to determine the competency of soil as a subgrade layer followed by preparation of sample with varying stabilizer content i.e. 4%, 6% and 8% cement by weight of dry soil, to determine the optimum stabilizer content. Samples with varying cement content were also prepared for California Bearing Ratio (hereafter, CBR) and Unconfined Compressive Strength (hereafter, UCS)with different curing periods i.e. 7 days for CBR and 3, 7, 14 and 28 days for UCS. UCS test on these sample showed a significant improvement over the values of natural soil without stabilizer. CBR showed a similar trend and the resulting modified soil was competent enough to be used as a subgrade for heavy traffic condition. The pavement was modelled using Kenpave for 30 and 50 million standard axle (msa) traffic intensity to determine the ideal pavement section for two types of pavement used in this study. In addition, the cost of construction for replacement method and for cement stabilization are determined using norms of Department of Road and District rate of Kathmandu and are compared. The cement stabilized soil with optimum content is found to be cheaper than conventional method of replacement.

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.

The Influence of Organic Matter on Phosphorus Fixation in Soils from the Eastern Flank of Mount Cameroon

The maximum phosphate fixation (KF) and phosphorus sorption capacity (PSC) of soil samples collected from the surface and sub-surface horizons of five volcanic soil profiles from the eastern flank of Mount Cameroon were investigated before and after organic matter removal. The aim of this research was to investigate the influence of soil organic matter (OM) on phosphorus (P) fixation. The removal of soil OM from the soil samples was accomplished by the use of sodium hypochlorite. Phosphorus fixation studies were performed on the treated and untreated soil samples using calcium chlorite as the background electrolyte. Fixation data were interpreted with Freundlich adsorption isotherm. The results indicated that the removal of OM had an influence on both KF and PSC. Removal of soil OM decreased PSC and increased KF for all soils. The inhibition of aluminium oxide and the reduction of soil surface area after the removal of OM were the justifications for the increase in P fixation.

Investigations of graphene oxides and cement on strength performance of soil

Recent studies confirm the ability of graphene oxides (GO) for the improvement of cementitious-based soil material properties. The current study aimed to explore the influence of GO and cement on the spectroscopic, thermal, structural, and strength of soil experimentally. The spectroscopic analysis studied by FTIR showed the presence of GO and cementitious contents in the soil sample by detecting the vibration modes of respective components. Thermal (TGA) analysis revealed a slight loss in weight with the increase in temperature up to 1000 °C majorly due to the presence of moisture contents. SEM equipped with an EDX technique was implemented to examine the sample of microstructure containing GO. X-ray diffraction (XRD) recorded patterns confirmed the configuration of mineralogical contents of soil modified with GO and cement. For mechanical properties, composites samples were prepared at different concentrations of GO (0.03, 0.05, 0.1 wt% of cement) and cement (5, 10, 15, 20 wt% of the soil) to evaluate compaction characteristics, unconfined compression strength (UCS) and swelling parameters. The experimental outcomes portrayed that the increment in GO content causes prompt improvement in compressive strength (nearly 10 times compared with untreated soil sample) and reduces swelling pressure of treated soil tests. UCS behavior was boosted with the GO contents in the samples. Results depicted that the GO as an alleviating agent has significant impact on the physical features of expansive soil that will be beneficial for the construction of roads, dams, and bridges.

Risk factors associated with the prevalence of Shiga-toxin-producing Escherichia coli in manured soils on certified organic farms in four regions of the USA

IntroductionBiological soil amendments of animal origin (BSAAO), including untreated amendments are often used to improve soil fertility and are particularly important in organic agriculture. However, application of untreated manure on cropland can potentially introduce foodborne pathogens into the soil and onto produce. Certified organic farms follow the USDA National Organic Program (NOP) standards that stipulate a 90- or 120-day interval between application of untreated manure and crop harvest, depending on whether the edible portion of the crop directly contacts the soil. This time-interval metric is based on environmental factors and does not consider a multitude of factors that might affect the survival of the main pathogens of concern. The objective of this study was to assess predictors for the prevalence of Shiga-toxin-producing Escherichia coli (non-O157 STEC) in soils amended with untreated manure on USDA-NOP certified farms.MethodsA longitudinal, multi-regional study was conducted on 19 farms in four USA regions for two growing seasons (2017–2018). Untreated manure (cattle, horse, and poultry), soil, and irrigation water samples were collected and enrichment cultured for non-O157 STEC. Mixed effects logistic regression models were used to analyze the predictors of non-O157 STEC in the soil up to 180 days post-manure application.Results and discussionResults show that farm management practices (previous use with livestock, presence of animal feces on the field, season of manure application) and soil characteristics (presence of generic E. coli in the soil, soil moisture, sodium) increased the odds of STEC-positive soil samples. Manure application method and snowfall decreased the odds of detecting STEC in the soil. Time-variant predictors (year and sampling day) affected the presence of STEC. This study shows that a single metric, such as the time interval between application of untreated manure and crop harvest, may not be sufficient to reduce the food safety risks from untreated manure, and additional environmental and farm-management practices should also be considered. These findings are of particular importance because they provide multi-regional baseline data relating to current NOP wait-time standards. They can therefore contribute to the development of strategies to reduce pathogen persistence that may contribute to contamination of fresh produce typically eaten raw from NOP-certified farms using untreated manure.

On the use of biocementation to treat collapsible soils

The effectiveness of biocementation to treat the collapse potential of a well graded sand is investigated. The novelty on the application of this treatment for this purpose is that the analysis is done considering structural changes experienced by the soil during the treatment and not only in service. Oedometer tests were performed on treated and untreated soil samples, both in saturated and unsaturated states, to study structural changes due to loading. The presence of biocement bond was confirmed by indirect tensile tests, and other complementary tests were performed to detect the presence of biocement and evaluate the efficiency of the treatment to reduce the collapse potential. Saturated permeability measurements, collapse tests and pore size distribution from mercury intrusion porosimetry tests confirmed the collapsible nature of the soil and that the treatment by bio-cementation reduces collapse potential. However, the treatment was effective not because of the presence of the biocement providing bonds to a metastable soil structure, but mainly because it requires the full saturation of the soil, therefore causing early collapse. Therefore, further collapse on rewetting of the treated soil is basically the second collapse, and for this reason the amplitude of the deformation observed reduces and the treatment is effective. Nevertheless, the physical bonds provided by the biocement precipitated were evident on the results of oedometer and indirect tensile tests, providing additional strength to the soil particles, and therefore some maintaining structure after the treatment. Therefore, the biocementation treatment to reduce the collapse potential is the junction of the treatments pre-wetting the soil, and those providing the reinforcement of the soil with binder, in this case with biological nature.

Effects of Fe oxide-based nanoparticles on yield and nutrient content of corn in Cobalt-contaminated soils

This study aimed to investigate the efficacy of Fe oxide nanoparticles (NPs) alleviating cobalt (Co) phytotoxicity in contaminated soils. The experiment was conducted in a greenhouse involving Fe oxide NPs (carboxymethylcellulose (CMC)-stabilised and non-stabilised (pure) hematite, goethite, and magnetite) and concentrations of soil total Co (5, 25, 65, 125, and 185 mg kg −1). Corn plant was grown in the treated and untreated soil samples and harvested after 60 days. Results indicated that by increasing the concentration of Co in soil from 5 to 25 mg kg −1, the growth parameters and the concentrations of K, P, Fe, and Zn in the shoots of corn increased. However, in soil samples with total Co concentrations of 25 to 185 mg kg −1, the growth and concentrations of nutrients in plant aerial parts declined. At low concentrations of Co (5 and 25 mg kg −1 soil), the application of pure Fe oxide NPs and composites inhibited corn growth as well as concentrations of plant nutrients in the shoots. At high concentrations of Co in soil, the application of treatments, especially stabilised goethite, reduced the accumulation of Co in the corn plant and enhanced its growth by increasing the concentrations of nutrients in plant aerial parts. This study suggests that the efficacy of treatments in enhancing corn growth depends on the total Co concentration of soil.

The Preliminary Study for Effect of Plant Extract on Concentration of Heavy Metals in Soil

Heavy metal contamination in soils had arisen into a more prominent problem as a result of increasing anthropogenic activities like manufacturing, mining, excessive application of agricultural chemicals and inappropriate disposal of wastes. Researchers across the globe had been striving to discover and develop methods to restore the soil back to its original condition with an assortment of remediation techniques that varies from treatment mechanism for various soil and contamination condition. Majority of the existing techniques have drawbacks like high energy consumption, specificity on the site condition, limitations on applicable contaminants, side effects after treatment, and also being uneconomical. More and more researchers are beginning to divert their attention into using organic stabilizers for treatment of soil heavy metal contamination in recent years after learning about its potential after numerous research showed promising reduction on the bioavailability and mobility of heavy metals. Due the lack of study on liquid-form organic stabilizers, the authors dedicated this research into implementing plant extract (TM) in the immobilization of heavy metals in soil. For comparison purpose, sodium alginate (SA), a proven organic stabilizer had been incorporated into the experiment to evaluate the performance of plant extract to immobilize cadmium (Cd), chromium (Cr), and manganese (Mn) from the metal-spiked soil samples in this research. The study findings suggested that the SA increased the unstable fractions, namely the exchangeable and carbonate fractions, of Cd relative to the untreated soil sample by 10.3 % to 5.2. On the other hand, the TM yields a result of 0.1 % to 1.1 % reduction of the unstable Cd. For the unstable Cr, both SA and TM decreased the concentration levels in the soil by 2.5 % to 8.0 % and 6.1 % to 7.9 % respectively. The results for Mn showed that the SA is able to decrease the concentration of its unstable fractions by 2.0 % to 7.5 % while the TM increases the concentration by 11.7 % to 1.5 %. In general, lower concentration of heavy metals in the unstable fractions was detected as the dosage of soil stabilizers applied increases. The application of soil stabilizers at 10 % weight percentage yields the lowest reading of unstable heavy metals in comparison with samples with lower dosage.

Deciphering the Fusarium-wilt control effect and succession driver of microbial communities managed under low-temperature conditions

The regulation of microbial communities is an important strategy to control the spread of soil-borne diseases. However, the control of soil-borne diseases through the regulation of microbial communities at low-temperature conditions, and the association of their succession with abiotic factors during plant cultivation are not well characterised. In this study, the effects of various soil-disinfestation strategies, i.e. soil irrigated to saturation (SA), reductive soil disinfestation (RSD) and ammonia fumigation (AF), on the prevention of watermelon Fusarium wilt as well as the interaction of microbial community succession and abiotic factors were determined. The abundance of F. oxysporum in soil samples subjected to SA, RSD and AF treatments decreased significantly by 86.09%, 90.67% and 93.68%, respectively, compared with the untreated soil sample. RSD and AF treatments established significantly different microbial α- and β-diversities and physicochemical properties, whereas SA treatment showed no significant effect on these properties. After planting, RSD- and AF-treated soils exhibited significantly reduced disease incidence and increased the watermelon yield, respectively, whereas SA-treated soil showed no significant effects. The physicochemical and microbial characteristics of treated soils were similar to those of untreated diseased soil. Moreover, the differences in soil physicochemical characteristics remarkably and positively correlated with the dissimilarities in microbial communities. For the differences in bacterial and fungal β-diversities, soil pH was determined to have the highest mean predictor importance value. Potentially beneficial microbes were identified mainly after RSD and AF treatments; however, the relative abundances of these microbes were closely associated with soil pH and significantly decreased after planting. Overall, the soil-borne pathogens reduced and microbial community improved by RSD and AF treatments at low-temperature conditions could effectively control soil-borne diseases. Soil pH plays a pivotal role in restoring the microbial community during watermelon cultivation.

Understanding the Effect of Pulp Mill Fly Ash on Strength, Compressibility, and Microstructure of Organic Soil

A lower shear strength and higher compressibility impose major challenges for construction on organic soils. Cementitious materials have been effectively used in the improvement of the engineering properties of mineral soils with low organic contents. However, limited studies have been devoted to the stabilization of the organic soils commonly encountered in forested regions in Canada. The present study investigated the effects of pulp mill fly ash (PFA) on the compressibility of a natural soil consisting of 26% organic matter. Fall-cone and oedometer tests were conducted on organic soil mixed with different PFA dosages (5%, 10%, 20%, 30%, 40%, and 50%), as well as on untreated soil samples. The mineralogical and microstructural aspects of PFA-treated organic soil were examined using scanning electron microscope and energy-dispersive X-ray spectroscopy techniques. The results suggest that when the organic soil was treated with PFA, its undrained shear strength and compressibility behavior were improved. Moreover, the potentially large settlement of organic soil can be reduced by the addition of PFA. The primary and secondary compression index (Cc and Cα, respectively) values decreased significantly when compared with the untreated organic soil, indicating that PFA stabilizers can effectively improve the creep behavior of organic soils. These findings indicate that the beneficial utilization of PFA for the stabilization of organic soils could be a practical step toward the environmentally sound management of this waste byproduct.

Innovative Polycomposite Fertilizer Obtained by Recycling and Processing Three Organic Wastes

The paper aims at testing an innovative organic fertilizer obtained from waste by processing a mixture of marine algae biomass, sewage municipal sludge and farmyard manure. Design of this polycomposite fertilizer is based on adequate conceptual and experimental models by taking into account the complex interactions among these three biomasses. In the first step a detail physico-chemical analysis has been performed on the composition of the three raw materials and also on the soil. In the second phase similar analyses have been carried out on representative samples of soil treated with the compost as compared with untreated soil samples. Analytical methods applied were FT-IR spectroscopy in correlation with organic/inorganic and total carbon (TOC/TIC/TC) analysis. The efficiency of applying this compost on the field at large scale has been assessed by means of fatty acid content of the oleaginous plants cultivated. Based on correlation between production quality and chemical composition of the composted soil, the optimal proportions of the mixture of the three organic wastes will be selected for designing an eco-friendly fertilizer able to improve agrochemical properties of the soil.

Analysis of Multiresidue Pesticides in Agricultural Paddy Soils Near Industrial Areas in Korea by GC–MS/MS and LC–MS/MS Using QuEChERS Extraction with dSPE Clean-Up

Pesticides have been used to control pests in agricultural fields and storage systems before circulating agricultural products to markets. A tandem mass spectrometry, equipped with gas chromatographic separation (GC–MS/MS) or ultra-performance liquid chromatographic separation (LC–MS/MS), was used to monitor residual pesticides in Korean rice paddy soils. Selective multiple reaction monitoring was employed during the analyses to achieve multiresidue pesticide analysis using GC–MS/MS and LC–MS/MS of 342 pesticides. In this study, QuEChERS extraction was employed with a dSPE clean-up to establish an effective pretreatment process. The limit of detection (LOD) and limit of quantification (LOQ) were set up for all pesticides, and method validation was performed for linearity and recovery at levels of 10 and 50 mg kg−1 in the untreated soil sample. All pesticides satisfied the acceptable recovery range of 70–120%, within less than 20% RSD values, except for ametoctradin and gibberellic acid. In the paddy soil analyses, tricyclazole was the most frequently detectable pesticide, followed by oxadiazon, endosulfan, and chlorantraniliprole. Continuous monitoring of residual pesticides in paddy soils should be conducted due to the translocation of some systemic pesticides from soils to crop plants, and the impact of residual pesticides on the environment.

Stabilization of Clayey Soil Using Cement Kiln Dust as Sustainable Material

One of the cornerstones of sustainability is reusing by-product waste materials that contribute to serious environmental problems. The current study presents the results of a series of laboratory tests using cement kiln dust (CKD) waste material as a soil stabilizer. A clayey soil was treated with four percentages of cement kiln dust (CKD) content of 5, 10, 15, and 20 by dry weight of the soil. To investigate the effect of the curing age on the behavior of the treated soil, different curing ages were considered such that; 1, 4, 7, 30, 60, and 90 day. The assessment of the improving rate of the treated soil was based on the outcomes of the compaction parameters, consistency limits, unconfined compressive strength, permeability, and durability (freezing-thawing and wetting-drying) tests. The results showed that the tested properties were improved substantially, and it is concluded that the optimum CKD content was 5% by dry weight of the soil. The unconfined compressive strength of treated soil samples with 5% CKD was increased by 43% for the age of one day and 238% after 90 days curing age compared with the untreated soil samples. The plasticity index was reduced by 7.9, 26.3, 43.1, and 57.9% for the soil treated with cement kiln dust (CKD) content of 5, 10, 15, and 20%, respectively. The coefficient of permeability of the treated soil was substantially reduced. Also, the findings show that the durability of the treated soil was improved appreciably, and this improvement is in proportion with increasing the percentage of CKD content for both (freezing-thawing) and (wetting-drying) tests.

Strength and Swelling Behavior of Black Cotton Soil Stabilized with Waste Rubber Tyre

Objectives: To determine the strength and swelling behavior of black cotton soil (expansive soil) using a shredded rubber tyre as an additive. Methods: Series of unconfined compressive strength and California Bearing Ratio (CBR) tests were carried out on black cotton soil mixed with 0%, 5%, 10%, and 15% of shredded rubber tyres, and the results were compared with untreated soil samples. The study also investigated the influence of shredded rubber on swelling characteristics of black cotton soil by performing the swelling pressure test. Findings: From the experimental results, it is inferred that the optimum addition of a 10% shredded rubber tyre can effectively improve the strength behavior of black cotton soil. The unconfined compressive strength and California Bearing Ratio (CBR) of soil stabilized with 10% of shredded rubber tyre increased by 32 % and 49.3% respectively as compared to the untreated soil. An illustration presented shows the effect of increased CBR in terms of the reduction of 18% pavement thickness. This may reduce the total cost of the project. The present study also investigated the swelling potential of Black cotton soil and it is found to be decreased by 33.33% for the addition of 15% shredded rubber soil as compared to untreated soil. Novelty: The use of shredded rubber in expansive soil increased its CBR value, leading to a reduction in 18% of pavement thickness. Hence, it may lead to a further reduction in the total cost of the project. Also, the disposal problem of waste rubber tyres is resolved up to a certain extent. Keywords: Shredded Rubber Tyre; Black Cotton Soil; Unconfined Compressive Strength; California Bearing Ratio; Soil Stabilization

Physical stabilization of expansive subgrade soil using locally produced geogrid material

This paper illustrates application of a locally produced geogrid material for strength improvement of expansive subgrade soil. Samples of black, soft soil predominating the study area were collected from south western parts of Modjo town, inside the rift valley region of central parts of Ethiopia. X-Ray diffraction as well as index property tests were executed to identify and categorize the expansiveness of the highly plastic soft soil. The effects of two locally manufactured geogrid reinforcement materials; namely, polypropylene (PP) and high density polyethylene (HDPE) on the California bearing ratio (CBR) values of the expansive soil have been investigated. The test results indicated that the use of the geogrid reinforcement can significantly improve the bearing capacity of weak subgrade soil. The soaked CBR of the untreated soil sample, which was about 2.98%, was able to be raised to 10.16% and 7.48% by the application of PP and HDPE type of geogrid respectively, that were placed at 0.35H from the top of specimen. The research demonstrated the potential of using locally produced geogrid material for the improvement of weak subgrade soil.

Environmental relevance of adsorption of doxycycline, enrofloxacin, and sulfamethoxypyridazine before and after the removal of organic matter from soils

In this work batch-type experiments were used to study the adsorption of the antibiotics doxycycline (DC), enrofloxacin (ENR), and sulfamethoxypyridazine (SMP) in cultivation soils, before and after the removal of soil organic matter. Organic matter removal by calcination resulted not only in C and N removal, but also in increased soil pH, exchangeable basic cations and surface area values. The results indicate a very different behavior depending on the type of antibiotic, showing the adsorption sequence DC > ENR > SMP. Specifically, DC adsorption was very high in untreated soil samples (with organic matter), and was still high (although decreased) after the removal of soil organic matter. Furthermore, the adsorption behavior of DC was clearly dependent on the pH of the medium. Regarding ENR, it also showed high adsorption, although to a lesser extent than DC. However, when soil organic matter was removed, ENR adsorption significantly decreased in all soil samples. As regards SMP, it was adsorbed to a much lesser extent, and the removal of soil organic matter caused an additional drastic decrease in adsorption, reaching negligible values in some samples. Desorption followed the reverse sequence of adsorption, specifically in the order DC < ENR < SMP. In the case of DC, desorption was negligible, both in samples with and without organic matter, while for ENR and SMP, desorption clearly increased for soil samples where organic matter was removed. These results may be of relevance as regards environmental quality and public health, especially to facilitate a correct use of soils and organic amendments in areas that receive the application of substances containing the investigated antibiotics.