Showing papers on "Soil stabilization published in 2017"
TL;DR: A review of the use of MICP for soil improvement can be found in this article, where the authors discuss the treatment process including the primary components involved and major affecting factors, as well as the potential advantages and limitations.
Abstract: Biocementation is a recently developed new branch in geotechnical engineering that deals with the application of microbiological activity to improve the engineering properties of soils. One of the most commonly adopted processes to achieve soil biocementation is through microbially induced calcite precipitation (MICP). This technique utilizes the metabolic pathways of bacteria to form calcite (CaCO3) that binds the soil particles together, leading to increased soil strength and stiffness. This paper presents a review of the use of MICP for soil improvement and discusses the treatment process including the primary components involved and major affecting factors. Envisioned applications, potential advantages and limitations of MICP for soil improvement are also presented and discussed. Finally, the primary challenges that lay ahead for the future research (i.e. treatment optimization, upscaling for in situ implementation and self-healing of biotreated soils) are briefly discussed.
295 citations
TL;DR: In this article, the authors addressed the some fundamental and success soil improvement techniques used in civil engineering field and addressed the failure to identify the existence and magnitude of expansion of these soils in the early stage of project planning.
Abstract: Clayey soils are usually stiff when they are dry and give up their stiffness as they become saturated. Soft clays are associated with low compressive strength and excessive settlement. This reduction in strength due to moisture leads to severe damages to buildings and foundations. The soil behavior can be a challenge to the designer build infrastructure plans to on clay deposits. The damage due to the expansive soils every year is expected to be $1 billion in the USA, £150 million in the UK, and many billions of pounds worldwide. The damages associated with expansive soils are not because of the lack of inadequate engineering solutions but to the failure to identify the existence and magnitude of expansion of these soils in the early stage of project planning. One of the methods for soil improvement is that the problematic soil is replaced by suitable soil. The high cost involved in this method has led researchers to identify alternative methods, and soil stabilization with different additives is one of those methods. Recently, modern scientific techniques of soil stabilization are on offer for this purpose. Stabilized soil is a composite material that is obtained from the combination and optimization of properties of constituent materials. Adding cementing agents such as lime, cement and industrial byproducts like fly ash and slag, with soil results in improved geotechnical properties. However, during the past few decades, a number of cases have been reported where sulfate-rich soils stabilized by cement or lime underwent a significant amount of heave leading to pavement failure. This research paper addressed the some fundamental and success soil improvement that used in civil engineering field.
230 citations
TL;DR: In this paper, the effects of some key environmental parameters on ureolytic MICP mediated soils, including the impact of urease concentrations, temperature, rainwater flushing, oil contamination, and freeze-thaw cycling, were examined.
Abstract: Microbially induced calcite precipitation (MICP) is a sustainable biological ground improvement technique that is capable of altering and improving soil mechanical and geotechnical engineering properties. In this paper, laboratory column studies were used to examine the effects of some key environmental parameters on ureolytic MICP mediated soils, including the impact of urease concentrations, temperature, rainwater flushing, oil contamination, and freeze–thaw cycling. The results indicate that an effective crystal precipitation pattern can be obtained at low urease activity and ambient temperature, resulting in high improvement in soil unconfined compressive strength (UCS). The microstructural images of such crystals showed agglomerated large clusters filling the gaps between the soil grains, leading to effective crystals formation. The rainwater flushing was detrimental to the biocementation process. The results also indicate that traditional MICP treatment by the two-phase injection method did ...
223 citations
27 Jul 2017
TL;DR: In this article, the physical and chemical properties of soil in different types of stabilization methods are reviewed and its effect on soil indicate the reaction mechanism with additives, effect on its strength, improve and maintain soil moisture content and suggestion for construction systems.
Abstract: Soil stabilization is the process of improving the shear strength parameters of soil and thus increasing the bearing capacity of soil It is required when the soil available for construction is not suitable to carry structural load Soils exhibit generally undesirable engineering properties Soil Stabilization is the alteration of soils to enhance their physical properties Stabilization can increase the shear strength of a soil and/or control the shrink-swell properties of a soil, thus improving the load bearing capacity of a sub-grade to support pavements and foundations Soil stabilization is used to reduce permeability and compressibility of the soil mass in earth structures and to increase its shear strength The main objective of this paper is to review the physical and chemical properties of soil in different types of stabilization methods Stabilization and its effect on soil indicate the reaction mechanism with additives, effect on its strength, improve and maintain soil moisture content and suggestion for construction systems Soil stabilization can be accomplished by several methods All these methods fall into two broad categories namely mechanical stabilization and chemical stabilization Mechanical Stabilization is the process of improving the properties of the soil by changing its gradation and chemical stabilization of expansive soil comprises of changing the physico-synthetic around and within clay particles where by the earth obliges less water to fulfill the static imbalance and making it troublesome for water that moves into and out of the framework so as to fulfill particular designing road ventures
119 citations
TL;DR: In this paper, the efficiency of typical chemical and mechanical soil stabilization techniques in mitigating the swelling problem of an expansive soil is investigated through a comprehensive experimental study, where chemical stabilization was generated by traditional agents consisting of lime and cement, and by a commercially branded polymer (CBR PLUS).
Abstract: The efficiency of typical chemical and mechanical soil stabilization techniques in mitigating the swelling problem of an expansive soil is investigated through a comprehensive experimental study. Chemical stabilization was generated by traditional agents consisting of lime and cement, and by a commercially branded polymer (CBR PLUS). Mechanical stabilization was applied by means of fiber-reinforcement and swell–shrink cycles. Chemically-treated and fiber-reinforced soil samples were tested for swelling potential in a conventional oedometer apparatus; while swell–shrink cycles were applied using a modified temperature-controlled oedometer. Swell–shrink cycles were applied under room temperature for wetting cycles while the drying process was conducted under a constant temperature of 40 ± 5 °C, and swelling and shrinkage potential were recorded during successive cycles to a point in which swell–shrink equilibrium was attained. Typical strength tests were also conducted for each stabilization scenario which led to maximum reduction in swelling potential. In addition to the experimental program, the swell–time relationship for various stabilization scenarios was simulated using a two-parameter rectangular hyperbola function (2P-RH). Results indicated that all of the proposed stabilization scenarios can guarantee a significant reduction in swelling potential. In the case of lime and cement, reduction in swelling potential was observed to be a function of agent percentage and curing time; whereas for polymer-treated samples the effect of curing was found to be insignificant. Regarding fiber-reinforced samples, reduction in swelling potential was a function of fiber percentage, aspect ratio and fiber tensile strength. Overall, traditional agents proved to be more effective compared to non-traditional techniques. The proposed non-traditional methods, however, displayed promising results posing as great alternatives to lime and cement.
87 citations
TL;DR: In this article, the authors examined the effectiveness of SH-85, a new calcium-based powder additive which is prepared from biomass silica, for stabilization of a tropical residual laterite soil.
84 citations
TL;DR: In this article, an alternative stabilizer -Lignosulfonate (LS)-was used to improve the mechanical properties of high plasticity clay, such as Atterberg limits, proctor compaction, unconfined compressive strength (UCS), effect of cyclic wetting/drying on the strength properties, stress-strain behavior and secant modulus of elasticity.
Abstract: Many customary soil additives (e.g., cement, lime, fly ash and gypsum) are generally used to improve the mechanical properties of the soils. The applicability of most of these traditional stabilizers of soil is limited to particular soils. Moreover, traditionally stabilized soils in some cases exhibit high brittle behavior, which is oftentimes inappropriate for projects such as airport runways and embankments of railroads. This article presents the results of a research study in which an alternative stabilizer -Lignosulfonate (LS)- is investigated. Several basic properties of high plasticity clay, such as Atterberg limits, proctor compaction, unconfined compressive strength (UCS), effect of cyclic wetting/drying on the strength properties, stress-strain behavior and secant modulus of elasticity ( E 50 ) are assessed. To clarify the strength development due to the LS-treatment, scanning electron microscopy is performed on LS-treated and untreated clay. The LS contents were 0.5, 0.75, 1, 2, 3 and 4% by weight of the dry soil and specimens were cured for 0, 4, 7, 14, and 28 days. Results show that the LS-treatment leads to a considerable reduction in plasticity index (PI) of the soil. Also, stabilization with LS has slightly increased the optimum water content and slightly decreased the maximum dry unit weight of the soil. This stabilization has increased the stiffness and UCS of the soil without leading to a considerable brittle behavior. The increase in strength properties is ascribed to the electrostatic reaction that occurs between the mixture of LS-water and soil particles.
74 citations
TL;DR: In this paper, the viability of xanthan gum as an environmentally friendly stabilizer that can improve the engineering properties of tropical residual laterite soil was examined, and the results indicated that the additive was effective for the use of site-specific soils, providing an ecofriendly and sustainable alternative to traditional soil stabilization additives such as cement or lime.
Abstract: Many tropical residual laterites have relatively poor engineering properties due to the significant percentage of fine-grained soil particles that they contain, which are formed by the soil weathering process The widespread presence of laterite soils in tropical regions often requires that some form of soil improvement be performed to allow for their use in various civil engineering applications, such as for road base or subbase construction One of the most commonly utilized stabilization techniques for laterite soils is the application of additives that chemically react with the minerals that are present in soil to enhance its overall strength; effective soil stabilization can allow for the use of site-specific soils, and can consequently result in significant cost savings for a given project With an increasing focus on the use of more environmentally friendly and sustainable materials in the built and natural environments, there is an emerging interest in eco-friendly additives that are an alternative to traditional chemical stabilizers The current study examines the viability of xanthan gum as an environmentally friendly stabilizer that can improve the engineering properties of tropical residual laterite soil Unconfined compressive strength (UCS) tests, standard direct shear tests, Brunauer, Emmett, and Teller (N2-BET) surface area analysis tests and field emission scanning electron microscopy (FESEM) tests were used to investigate the effectiveness of xanthan gum for stabilization of a tropical laterite soil The UCS test results showed that addition of 15% xanthan gum by weight yielded optimum stabilization, increasing the unconfined compressive strength of the laterite soil noticeably Similarly, direct shear testing of 15% xanthan gum stabilized laterite specimens showed increasing Mohr–Coulomb shear strength parameters with increases in curing time From the FESEM results, it was observed that the stabilization process modified the pore-network morphology of the laterite soil, while also forming new white layers on the surface of the clay particles Analysis of the test results indicated that xanthan gum stabilization was effective for use on a tropical residual laterite soil, providing an eco-friendly and sustainable alternative to traditional soil stabilization additives such as cement or lime
68 citations
TL;DR: The main aim of this paper is to determine the optimum quantity of FA content for stabilization of this type of soil through particle size distribution and compaction tests and the results were in line with the literature for other types of soil.
59 citations
TL;DR: In this paper, the results of laboratory tests that were conducted to determine the proper treatment/stabilization recipe of very weak subgrade soils at high moisture contents, and to evaluate the corresponding performance-related properties [eg, the resilient modulus and permanent deformation] for use in the design of sustainable pavement structures were presented.
Abstract: This paper presents the results of laboratory tests that were conducted to determine the proper treatment/stabilization recipe of very weak subgrade soils at high moisture contents, and to evaluate the corresponding performance-related properties [eg, the resilient modulus and permanent deformation] for use in the design of sustainable pavement structures Four different subgrade soil types of different plasticity indices were considered in this study Three different moisture contents were selected at the wet-side of optimum that correspond to a raw soil strength value of 172 kPa (25 psi) or less All the soils were treated with different combinations of class C fly ash (or Portland cement type I) and hydrated lime to achieve a 7-day target strength values of 345 kPa (50 psi) to create a working platform and 690 kPa (100 psi) to stabilize the subgrade for subbase application Repeated load triaxial (RLT) tests were performed on laboratory molded specimens to evaluate their resilient modulus and permanent deformation behavior under cyclic loading The AASHTO T-307 procedure was followed in this study to conduct the resilient modulus tests A good correlation was observed between the water/additive ratio and the resilient modulus/permanent deformation, such that the soil specimens prepared at low water/additive ratio showed better performance than those prepared at high water/additive ratio The results of laboratory tests showed that the use of direct correlation between unconfined compressive strength (UCS) and resilient modulus for cementitiously treated/stabilized soils can be misleading
50 citations
TL;DR: In this article, the effectiveness of fly ash cement-improved Singapore marine clay (FACC) through tests including unconfined compression, split tensile, Bender element, and isotropic compression tests was discussed in detail by comparing its geotechnical properties with those of Ordinary Portland Cement-admixed clay.
TL;DR: The mechanisms of stabilization of the selected soils due to the use of EAFD along with a small quantity of cement are elucidated and considerably improve the mechanical properties and durability of both marl and sand.
Abstract: This paper reports the method and mechanism for improving the strength of marl and desert sand utilizing electric arc furnace dust (EAFD), an industrial by-product, in lieu of cement or lime. EAFD was used in conjunction with a small quantity (2%) of cement. The mechanical properties and durability characteristics of marl and sand mixed with 2% cement plus 5-, 10-, 20- or 30%-EAFD, by weight of the soil, were evaluated. The soil-cement-EAFD mixtures were used to determine their unconfined compressive strength (UCS), soaked California Bearing Ratio (CBR) and durability. The risk of leaching of toxic heavy metals, such as lead and cadmium, from the stabilized soils to the groundwater was also investigated. The mechanisms of stabilization of the selected soils due to the use of EAFD along with a small quantity of cement are also elucidated. The usage of 20 to 30% EAFD with 2% cement was noted to considerably improve the mechanical properties and durability of both marl and sand.
TL;DR: In this article, the geotechnical, micro-structure and engineering properties of marine clay are thoroughly reviewed and discussed and a guideline for the design and construction of projects on marine soils is provided.
Abstract: Marine clay is a soft soil that could be found widely at the coastal and offshore areas. This type of soil is usually associated with high settlement and instability, poor soil properties that are not suitable for engineering requirements and low unconfined compressive strength of less than 20 kPa. Considerable failure could occur even with light loads and it shows flat or featureless surface. This kind of soil is considered as problematic due to the existence of high moisture content and usually exists as slurry with noticeable percentage of expandable clay minerals. In this paper, the geotechnical, micro-structure and engineering properties of marine clay are thoroughly reviewed and discussed. The properties include moisture content, particle size distribution, specific gravity, Atterberg limits, mineral compositions and shear strength. Moreover, due to the increasing demand of construction at coastal and offshore areas involving the marine clay, many attempts have been made to stabilize this kind of soil in order to solve the geotechnical related problems. Some of the common stabilization methods used to improve the properties of marine clay such as cement grouting, chemical additives and some environmental friendly additives are discussed. In long term, marine clay treatment using cement was found to be the best method. In addition, this paper serves as a guideline for the design and construction of projects on marine soils.
08 May 2017
TL;DR: In this article, the erodibility parameters of dense silica sand specimens treated with different injection strategies were investigated at bench scale, in terms of greater and more uniform calcite precipitation over the test-specimen length, and hence greater erosion resistance.
Abstract: Hydraulic erosion is one of the main causes of failure within earth dams and embankments. Various methods are used to mitigate against such erosion, a common approach being grouting with cement, clay or chemical materials. Biogrouting using the microbial-induced carbonate precipitation technique is a relatively new, cost-effective, technically appropriate and environmentally friendly soil improvement method. Bacteria injected into the soil produce urease enzyme, which converts urea to ammonium and carbonate, causing calcite precipitation that binds soil grains together. In this study, the erodibility parameters of dense silica sand specimens treated with different injection strategies were investigated at bench scale. More effective treatment – in terms of greater and more uniform calcite precipitation over the test-specimen length, and hence greater erosion resistance – was achieved by aeration during solution injections and by incorporating a drained stage between injection cycles. With the latter, calc...
TL;DR: In this article, the authors highlight the importance of additive soil stabilization and highlight the advances in recent years with respect to chemical additive-based stabilization methods with a focus on resiliency and sustainability elements.
Abstract: Annual infrastructure damage expenses arising from expansive problematic soils cost millions of dollars. These damages signify the need to study the treatment methods in a much more comprehensive manner with a focus on resiliency and sustainability elements. Many advances are made in recent years with respect to chemical additive-based stabilization methods. This keynote paper covers innovative ground improvement advances majorly focusing on civil and transportation infrastructure. Four research studies highlighting the importance of additive soil stabilization are presented. Chemical stabilization advances ranging from shallow stabilization design guidelines with incorporation of fundamental soil chemistry principles, clay mineralogy, novel chemical additives, durability studies and resiliency elements are covered. Enhancement of soil strength due to the addition of lime and cement and the mixture’s resiliency to climatic changes are studied. Sustainable biopolymer treatments to arrest desiccation cracking on slopes have been addressed. In the case of deep soil treatment, deep soil mixing technologies are described for stabilization of soils to support pavement infrastructure. Future research directions related to sustainable ground improvement practices are presented.
TL;DR: In this article, the root system of alpine vegetation has been studied to quantify the effect of root density on soil aggregate stability in the forefield of the Lys glacier in the Aosta valley in Italy.
TL;DR: For example, in areas where expansive clay forms the bulk of the alignment soil, the common practice in Kenya is to remove the undesirable material, which is referred to as "clay removal" as mentioned in this paper.
Abstract: Pavement construction tends to be relatively expensive in areas where expansive clay forms the bulk of the alignment soil. The common practice in Kenya is to remove the undesirable material...
TL;DR: In this paper, the effect of carbon dioxide pressure and alkali concentration (10-M sodium hydroxide soil additions from 5 to 20%) between 7 and 90 days was evaluated using microscopic, spectroscopic, and diffraction techniques.
Abstract: This paper reports for the first time the stabilization of soil using olivine and the application of novel techniques utilizing alkaline activation and carbonation. A rigorous study addressed the effect of carbon dioxide pressure and alkali concentration (10-M sodium hydroxide soil additions from 5 to 20%) between 7 and 90 days. Microstructural and compositional changes were evaluated using microscopic, spectroscopic, and diffraction techniques. Results demonstrate the advantages of using olivine in the presence of NaOH and the associated increases in soil shear strength of up to 40% over 90 days. Samples subjected to carbonation for a further 7 days led to additional increases in soil strength of up to 60%. Microstructural investigations before and after carbonation attributed the strength development to the formation of Mg(OH)2, hydrated magnesium carbonates, and M─S─H, A─S─H gel phases. The impact of this work is far reaching and provides a new soil stabilization approach. Key advantages include significant improvements in soil strength with a lower carbon footprint compared with lime or cement stabilization.
TL;DR: The addition of lime has a pronounced effect on soft soils as mentioned in this paper, which is problematic because of their low strength, low bearing capacity, low permeability, and high compressibility.
Abstract: Soft soils are problematic because of their low strength, low bearing capacity, low permeability, and high compressibility. The addition of lime has a pronounced effect on such soils. In th...
TL;DR: In this paper, the effects of treating a soil having poor geotechnical properties with a bio-enzyme to determine its suitability for use as road pavement layer material was investigated.
Abstract: Soils with poor engineering properties have been a concern to construction engineers because of the need to strike a balance between safety and economy during earthworks construction. This research work investigates the effects of treating a soil having poor geotechnical properties with a bio-enzyme to determine its suitability for use as road pavement layer material. The elemental composition and microstructure of the soil was determined using energy dispersive X-ray spectroscopy and scanning electron microscopy, respectively. The specific gravity, Atterberg limits, compaction, strength and permeability characteristics of the soil was determined for various dosages of the bio-enzyme. The mountain soil is classified as clayey sand and A-2–4, according to unified soil classification and AASHTO classification systems, respectively. With increasing dosage of the bio-enzyme, the plasticity index, maximum dry unit weight and permeability of the soil decreased, while its 28-day California bearing ratio value, unconfined compressive strength and shear strength increased. Consequently, the application of bio-enzyme to the soil improved its plasticity and strength, and reduced its permeability. It, therefore, became more workable and its subgrade quality was improved for use as a road pavement layer material. The stabilized soil can be suitably used for constructing pavement layers of light-trafficked rural (earth) roads, pedestrian walkways and bicycle tracks.
TL;DR: In this article, the Giroud-Han method was calibrated to make geogrid junction stiffness in the cross-machine direction the primary property of the geosynthetic, thereby replacing geogrids aperture stability modulus.
Abstract: Geogrids and geotextiles are used routinely to stabilize weak subgrade soils during road construction. Typical subgrade stabilization applications are temporary haul roads or unpaved low-volume roads, but can also include paved roads built on poorer foundation materials. Full-scale test sections were constructed, trafficked and monitored to compare the relative operational performance of geosynthetics used as subgrade stabilization, as well as determine which material properties were most related to performance. Unpaved test sections were constructed using twelve geosynthetics consisting of a variety of geogrids and geotextiles. Multiple control test sections were also built to evaluate the effect that subgrade strength, base course thickness, and/or presence of the geosynthetic had on performance. Even though the geotextile materials used during this study showed good performance as subgrade stabilization, material properties associated with their performance was difficult to establish due to the limited number of test sections and lack of relevant tests to properly characterize these types of materials for this application. Using longitudinal rut as the primary indicator of performance, it was determined through a linear regression analysis that the stiffness of the geogrid junctions in the cross-machine direction correlated best with performance in this application and under these conditions. Using this knowledge, the design equation associated with the Giroud–Han method was calibrated to make geogrid junction stiffness in the cross-machine direction the primary property of the geosynthetic, thereby replacing geogrid aperture stability modulus. The calibration and verification of this method is described herein.
TL;DR: In this article, experimental results achieved by the use of granulated blast furnace slag (GBFS) and cement in stabilizing lithomargic clay for geotechnical applications.
Abstract: Utilizing industrial byproducts in soil stabilization benefits the economic, environmental and social benefits. Granulated blast furnace slag is a byproduct of iron and steel industry having oxides similar to that of cement but in different proportions. This study describes experimental results achieved by the use of granulated blast furnace slag (GBFS) and cement in stabilizing lithomargic clay for geotechnical applications. Soil was replaced by GBFS in percentages of 10, 15, 20, 25, 30, 35, 40, 45, 50% and cement of 2, 4, 6, and 8% by dry weight of soil is added. Various experimental studies like specific gravity, Atterberg limits, compaction, UCS, CBR and triaxial compression test, were performed on samples to understand the effect of these mixes on their few index and strength properties. The study also includes an investigation on a combination of optimum percentage of GBFS with varying percentage of cement and lime on their shear parameters. The study result shows significant improvement in the strength properties of the mixes. Hence it can be concluded that lithomargic clay stabilized with GBFS and cement/lime satisfy the strength requisite to be employed in the numerous geotechnical applications.
TL;DR: In this paper, the authors investigated the stress strain behavior, peak stress and ultimate strain of clayey soil stabilized by slag and slag-fly ash blending by alkali activation and found that peak stress as high as 25.0 n/mm2 may be obtained at 50% slags content when 12 molar sodium hydroxide solutions were used.
Abstract: Clayey subgrade soil requires treatment in order to make the subgrade stable for pavement structures. Treatment of clayey soil i.e. stabilization of clayey soil by cement, lime, and fly ash are established techniques used in geotechnical and highway engineering. Stabilization by alkali activation of fly ash is reported recently but literatures are limited. Present study investigates the stress strain behavior, peak stress and ultimate strain of clayey soil stabilized by slag and slag-fly ash blending by alkali activation. The peak stress as high as 25.0 N/mm2 may be obtained at 50% slags content when 12 molar sodium hydroxide solutions were used. Peak stress, ultimate strain and slope of stress–strain curve of stabilized clay are controlled by Na/Al and Si/Al ratios. Stress–strain response and peak stress of slag and fly ash blended specimen are not governed by Na/Al and Si/Al ratios; rather the behavior is dependent predominantly on slag content.
TL;DR: In this paper, a new hydration product of calcium aluminate chloride hydrate, also known as Friedel's salt, appeared in the PC+CH-stabilized chloride saline soils.
Abstract: In the field of soil stabilization, only calcium silicate hydrate (CSH) and ettringite (AFt) as hydration products have been reported to directly contribute to the strength enhancement of the soil. A chloride dredger fill, an artificial chloride saline soil, and a non-saline soil were stabilized by Portland cement (PC) and PC with Ca(OH)2 (CH) with different contents. A series of unconfined compressive strength (UCS) tests of stabilized soil specimen after curing for 7 d and 28 d were carried out, and the hydration products and microstructure of the specimens were observed by X-ray diffractometry (XRD), scanning electronic microscopy (SEM), and energy-dispersive X-ray analysis (EDXA). The results showed that the strengths of PC+CH-stabilized chloride saline soils were much higher than those of PC-stabilized soils. A new hydration product of calcium aluminate chloride hydrate, also known as Friedel’s salt, appeared in the PC+CH-stabilized chloride saline soils. The solid-phase volume of Friedel’s salt expanded during the formation of the hydrate; this volume filled the pores in the stabilized soil. This pore-filling effect was the most important contribution to the significantly enhanced strength of the PC+CH-stabilized chloride saline soils. On the basis of this understanding, a new optimized stabilizer was designed according to the concept that the chloride in saline soil could be utilized as a component of the stabilizer. The strength of the chloride saline soils stabilized by the optimized stabilizer was even further increased compared with that of the PC+CH-stabilized soils.
TL;DR: In this article, the effect of microbial induced calcite precipitation on the shear strength of a swelling fine-grained soil has been studied by means of laboratory-scale tests and the influence of bacterial concentration as well as the chemicals used in the treatment (culture media) have been looked into.
Abstract: In many engineering projects, improving soil shear strength is one of the goals. There are different methods for soil improvement among which biological soil stabilization techniques have emerged in recent decades. These techniques have been introduced as environmentally friendly techniques and have been shown to give promising results. However, different aspects of their effect on the soil mechanical properties have not yet been comprehensively understood. One of these aspects is the effect of different ingredients such as the effect of culture media as well as bacterial concentration on the improvement in the soil shear strength. In this study, the effect of one of the most commonly used biological stabilization techniques, namely microbial induced calcite precipitation on the shear strength of a swelling fine-grained soil has been studied by means of laboratory-scale tests and the influence of bacterial concentration as well as the chemicals used in the treatment (culture media) have been looked into. The results have been carefully analyzed and presented in terms of suitable formulas for practical purposes. Furthermore, the mechanisms contributing to the shear strength increase have been discussed based on the observed changes in the soil micro-fabric disclosed by X-ray diffraction analysis. The results reveal that by increasing bacterial concentration, the soil cohesion and the soil friction angle increase for which empirical relationships are presented. The increase in bacterial concentration thus increases the soil shear strength. Furthermore, the effect of culture media on the soil mechanical properties is examined. While the sole use of culture media slightly increases the soil shear strength, its impact on the soil shear strength is much less than that of the complete biological solution which includes bacteria. This proves the hypothesis that the improvement is indeed induced by the bio-geo-chemical processes which bacteria bring about rather than the chemical compounds present in the biological solution.
TL;DR: In this article, a technique for stabilizing poor soils is proposed, which is a technique that can improve engineering properties for road building, and chemical stabilizers such as cement and lime are commonly employed.
Abstract: Stabilization of poor soils is a technique that can improve engineering properties for road building. Chemical stabilizers such as cement and lime are commonly employed. However, environmen...
TL;DR: In this paper, the effect of using lime, natural pozzolana or a combination of both lime and natural pozolana on plasticity, compaction and shear strength of two clayey soils classified as CH and CL according to the unified soil classification system (USCS).
Abstract: Cohesive soils with a high plasticity index present difficulties in construction operations because they usually contain expansive clay minerals. However, the engineering properties of soils can be improved by different techniques. The aim of this paper is to study the effect of using lime, natural pozzolana or a combination of both lime and natural pozzolana on plasticity, compaction and shear strength of two clayey soils classified as CH and CL according to the unified soil classification system (USCS). The obtained results indicated that for CH class clay soil, the plasticity index decreased significantly for samples stabilized with lime. On the other hand, for the soil classified as CL class clay, a high decrease in the plasticity index value was observed for samples stabilized with natural pozzolana compared to those stabilized with lime. Also, both the cohesion and internal friction angle in lime added samples were demonstrated to increase with time. The combination of lime and natural pozzolana exhibits a significant effect on the enhancement of both the cohesion and internal friction angle at later stages. The lime-natural pozzolana combination appears to produce higher shear strength parameters than lime or natural pozzolana used alone.
TL;DR: In some cases, the production of solid waste is experiencing an uncontrolled and continuous increase, especially wastes from plastic products as mentioned in this paper, given that the process of transforming plastic waste into raw material involves high energy consumption, plastic can be used in geotechnical engineering works.
TL;DR: In this article, the polypropylene waste fiber was utilized to further improve the properties of cement kiln dust stabilized soil, which can be used in stabilization of soils and wastes, production of cement, agricultural and cement concrete products.
Abstract: Use of waste materials in ground improvement and soil stabilization is becoming important because of increasing costs of waste disposal and environmental considerations. Cement kiln dust is one of the waste materials obtained as by-product of cement manufacturing process the disposal of which is not manageable and poses serious environmental threat. The cement kiln dust can be used in stabilization of soils and wastes, production of cement, agricultural and cement concrete products. This experimental work focuses on study of different characteristics of clayey soil using waste cement kiln dust obtained from nearby cement factory. The polypropylene waste fiber was utilized to further improve the properties of cement kiln dust stabilized soil. Proctor compaction, unconfined compressive strength, California bearing ratio and split tensile strength tests were performed at different percentages of cement kiln dust without fiber and with optimum fiber content. The compaction characteristics were observed to improve with the maximum dry density occurring at 12% cement kiln dust. The results reveal that both unconfined compressive and split tensile strengths increase with curing period and the maximum values achieved at 12% cement kiln dust. The compaction and strength characteristics were observed to improve at the optimum content of polypropylene waste fiber.
22 Mar 2017
TL;DR: In this article, the formation of cementitious compounds was observed in mixtures of soil with different rice husk ash and lime contents, and unconfined compression strength tests were conducted on soils treated with RHA and lime.
Abstract: Rice husk ash (RHA) is a by-product of rice milling. Its use as a soil stabilizer is an alternative to the final disposition with environmental benefit. Because RHA is not self-cementitious, a hydraulic binder such a lime must be added to form cements to improve the soil strength. Researches on stabilization by applying RHA and lime combinations were conducted in sandy soils. RHA of no-controlled rice husk incineration in conventional ovens and of laboratory burning at controlled temperatures were used. The alkaline reactivity of the RHA was studied through X-ray diffractometry analysis and loss on ignition tests. The formation of cementitious compounds was observed in mixtures of soil with different RHA and lime contents. Unconfined compression strength tests were conducted on soils treated with RHA and lime. Results show strength improvements for all RHA and lime contents and time periods studied, and all materials produced can be defined as modified rather than stabilized. Improvement of sandy soils with RHA is an alternative to the final disposition with environmental, social and economic benefits.