Showing papers on "Soil stabilization published in 2016"

Introduction of Microbial Biopolymers in Soil Treatment for Future Environmentally-Friendly and Sustainable Geotechnical Engineering

Abstract: Soil treatment and improvement is commonly performed in the field of geotechnical engineering. Methods and materials to achieve this such as soil stabilization and mixing with cementitious binders have been utilized in engineered soil applications since the beginning of human civilization. Demand for environment-friendly and sustainable alternatives is currently rising. Since cement, the most commonly applied and effective soil treatment material, is responsible for heavy greenhouse gas emissions, alternatives such as geosynthetics, chemical polymers, geopolymers, microbial induction, and biopolymers are being actively studied. This study provides an overall review of the recent applications of biopolymers in geotechnical engineering. Biopolymers are microbially induced polymers that are high-tensile, innocuous, and eco-friendly. Soil–biopolymer interactions and related soil strengthening mechanisms are discussed in the context of recent experimental and microscopic studies. In addition, the economic feasibility of biopolymer implementation in the field is analyzed in comparison to ordinary cement, from environmental perspectives. Findings from this study demonstrate that biopolymers have strong potential to replace cement as a soil treatment material within the context of environment-friendly construction and development. Moreover, continuing research is suggested to ensure performance in terms of practical implementation, reliability, and durability of in situ biopolymer applications for geotechnical engineering purposes.

Stabilisation of marginal lateritic soil using high calcium fly ash-based geopolymer

Abstract: Marginal soils are traditional stabilised with Portland Cement (PC) when used as a pavement material. The production of PC is however an energy-intensive process and emits a large amount of greenhouse gas into the atmosphere. Geopolymer is an environmentally friendly ‘green’ binder commonly used in building applications but rarely used in pavement applications. The application of geopolymer to marginal soil stabilisation is an innovative approach given the increasing scarcity of virgin quarry materials in many countries. This research investigates the effects of alkali activator and curing time on unconfined compressive strength (UCS) and microstructural characteristics of marginal lateritic soil (LS) stabilised with high calcium fly ash (FA)-based geopolymer, which is novel in the field of pavement geotechnics. The viability of using this stabilised material as a bound pavement material was also evaluated through laboratory evaluation tests. A liquid alkali activator was a mixture of sodium silicate (Na2...

Xanthan gum biopolymer: an eco-friendly additive for stabilization of tropical organic peat

Abstract: Biogeotechnology is a recently established branch of geotechnical engineering, associated with the practical uses of microbiological techniques to improve the engineering properties of geomaterials. This study explores the utility of xanthan gum, an eco-friendly biopolymer obtained from microbial sources, for stabilization of tropical organic peat, using a series of macroscale and microscale test approaches. At the macroscale, the shear strength characteristics of both untreated and stabilized peat were evaluated using unconfined compression strength (UCS) and standard direct shear tests. Microscopic techniques, including field emission scanning electron microscopy (FESEM), Brunauer, Emmett, and Teller (N2-BET) surface area analysis, and particle size analysis, were also utilized to examine changes in the microstructural characteristics of stabilized peat that are caused by the chemical reaction that occurs between the xanthan gum and peat particles. UCS test results showed that the xanthan gum stabilization significantly improved the shear strength of the peat in its natural condition, with the 28-day strength of the stabilized peat being six times higher than the strength of the untreated peat. Microstructural analysis showed that the morphological characteristics of the peat are changed due to the chemical reaction that occurs during the curing process, as indicated by the FESEM results. Over time, formation of cementitious products was clearly observed, which welded peat particles and filled the pores in the soil structure, yielding a denser soil fabric with less pore volume and stronger attractive forces. From the testing that was performed, xanthan gum stabilization is recommended for peat as an eco-friendly and sustainable alternative to traditional soil stabilization additives such as cement or lime.

Advances in ground modification with chemical additives: From theory to practice

Abstract: This keynote paper describes recent advances in chemical stabilization with a particular focus on applications related to transportation infrastructure. Chemical stabilization advances ranging from stabilization design guidelines with incorporation of fundamental soil chemistry principles to novel chemical additives for future stabilization are covered. This paper focuses on chemical treatments of shallow to moderate subgrade depths for supporting transportation pavement infrastructure. A background summary of stabilization methods along with modifications to the current design practices is presented. This section is followed by a comprehensive experimental program on chemical treatments of expansive subsoils. Both clay mineralogy influence and durability issues are fully addressed. Stabilization leachate studies and their implication in relation to real field performance are also addressed. The final outcome of this research is a more comprehensive stabilization methodology that addresses soil types and performance based testing methodologies. The last two sections cover a brief summary of new treatments of immense interest to addressing sustainable elements in ground improvement practices.

Influence of zeolite and cement additions on mechanical behavior of sandy soil

Abstract: It is well known that the cemented sand is one of economic and environmental topics in soil stabilization. In this instance, a blend of sand, cement and other materials such as fiber, glass, nanoparticle and zeolite can be commercially available and effectively used in soil stabilization in road construction. However, the influence and effectiveness of zeolite on the properties of cemented sand systems have not been completely explored. In this study, based on an experimental program, the effects of zeolite on the characteristics of cemented sands are investigated. Stabilizing agent includes Portland cement of type II and zeolite. Results show the improvements of unconfined compressive strength (UCS) and failure properties of cemented sand when the cement is replaced by zeolite at an optimum proportion of 30% after 28 days. The rate of strength improvement is approximately between 20% and 78%. The efficiency of using zeolite increases with the increases in cement amount and porosity. Finally, a power function of void-cement ratio and zeolite content is demonstrated to be an appropriate method to assess UCS of zeolite-cemented mixtures.

Industrial Wastes as Auxiliary Additives to Cement/Lime Stabilization of Soils

Abstract: Chemical stabilization involves the use of chemical agents for initiating reactions within the soil for modification of its geotechnical properties. Cement and lime stabilization have been the most common stabilization methods adopted for soil treatment. Cement stabilization results in good compressive strengths and is preferred for cohesionless to moderately cohesive soil but loses effectiveness when the soil is highly plastic. Lime stabilization is the most preferred method for plastic clays; however, it proves to be ineffective in sulphate rich clays and performs poorly under extreme conditions. With such drawbacks, lots of researches have been undertaken to address the issues faced with each stabilization method, in particular, the use of solid wastes for soil stabilization. Solid waste reuse has gained high momentum for achieving sustainable waste management in recent times. Research has shown that the use of solid wastes as additives with and replacement for conventional stabilizers has resulted in better results than the performance of either individually. This review provides insight into some of the works done by earlier researchers on lime/cement stabilization with industrial wastes as additives and helps to form a sound platform for further research on industrial wastes as additives to conventional stabilizers.

Effect of Nano-SiO2 on the Geotechnical Properties of Cohesive Soil

Abstract: With the reduction of available land resources, the construction of civil engineering structures is carried out on soft soil, which leads to the development of ground improvement techniques such as soil stabilization. This research is intended to study the effect of adding nano-SiO2 on soil engineering properties, especially the shear strength and the unconfined compression strength and maximum dry unit weight, using clayey soil with low liquid limit (CL). Nano-SiO2 was mixed with soil in three different percentages (i.e. 0.5, 0.7, 1.0 % by weight of the parent soil). The shear strength, unconfined compression strength and maximum dry unit weight of treated specimens were measured by direct shear test, unconfined compression test and compaction test. It was found that increase in nano-SiO2 content resulted in increase in the angle of internal friction, the cohesion, the unconfined compression strength and maximum dry unit weight of the clayey soil. Based on the obtained results, in order to reach the maximum increase in strength parameters, the optimum nano-SiO2 content occurs at 0.7 %.

Effect of fly ash, construction demolition waste and lime on geotechnical characteristics of a clayey soil: a comparative study

Abstract: Improvement of strength and subgrade characteristics of soil by stabilization is one of the popular techniques nowadays. The use of construction demolition (C&D) waste in soil stabilization is still under research as much work has not been done in this area. This paper presents a comparative study of utilization of fly ash, C&D waste and lime in soil stabilization. A number of tests such as differential free swell, pH, compaction, unconfined compressive strength (UCS) and California bearing ratio (CBR) were conducted to study the effect of addition of fly ash, C&D waste and lime on geotechnical characteristics of soil. Based on results, it is concluded that differential free swell and maximum dry density decrease, whereas pH, UCS and soaked CBR value increase with addition of fly ash, C&D waste and lime. The increase in UCS is almost the same for lime and C&D waste at 7 days which indicates that the usage of C&D waste compared with that of lime is economical, whereas if used in pavement subgrade lime is better material because of higher CBR value. The UCS at 28 days is more for fly ash compared with that for lime and C&D waste.

Biomimetic Hydrogel Composites for Soil Stabilization and Contaminant Mitigation

Abstract: We have developed a novel method to synthesize a hyper-branched biomimetic hydrogel network across a soil matrix to improve the mechanical strength of the loose soil and simultaneously mitigate potential contamination due to excessive ammonium. This method successfully yielded a hierarchical structure that possesses the water retention, ion absorption, and soil aggregation capabilities of plant root systems in a chemically controllable manner. Inspired by the robust organic–inorganic composites found in many living organisms, we have combined this hydrogel network with a calcite biomineralization process to stabilize soil. Our experiments demonstrate that poly(acrylic acid) (PAA) can work synergistically with enzyme-induced carbonate precipitation (EICP) to render a versatile, high-performance soil stabilization method. PAA-enhanced EICP provides multiple benefits including lengthening of water supply time, localization of cementation reactions, reduction of harmful byproduct ammonium, and achievement of ...

Laboratory Investigation in the Improvement of Subgrade Characteristics of Expansive Soil Stabilised with Coir Waste

Abstract: Soft soils form problematic subgrade for pavements due to its low bearing capacity and strength. Pavement loads coming on the soft subgrade soil may cause detrimental pumping actions when they are located in areas with high water table which causes both construction and in-service performance problems. The common solutions on encountering such problems include excavation and replacement of soil, lime treatment or chemical stabilization. Excavation and replacement of soil becomes very expensive especially when usable soils have to be hauled to significant distance. Stabilization using various additives can improve the properties of soft soils. A recent trend in stabilization is to utilize locally available industrial wastes to improve the properties of soft soils. This method has the dual advantage of increasing the strength of soil and a solution for the problematic disposal of such wastes. Coir waste consisting of coir pith and coir fibre is a by-product of coir manufacturing industry obtained from coconut husk during the extraction of coir fibre. The pollution caused due to the polyphenol leaching and the resistance to degradation due to the stable lignin structure makes the coir waste a potential threat to the land resources. This paper presents an investigation on the behavior of soft soil stabilized with varying percentages of coir pith (0-3%) and coir fibre (0-1%) by carrying out Standard Proctor, Static Triaxial test and California Bearing Ratio(CBR) tests. The test results showed that stabilization with coir waste had a significant effect on the compaction, Elastic modulus as well as CBR characteristics.

Behavior of Geosynthetic Reinforced Soil Foundation Systems Supported on Stiff Clay Subgrade

Abstract: A series of laboratory model tests was performed to investigate the behavior of geosynthetic reinforced stiff clay foundation systems under circular loading. The footing consisted of a rigid circular steel plate with a diameter of 150 mm. Five different series of tests were performed in both homogeneous (clay or sand) and layered configurations. The tests used planar geogrid and three-dimensional geocell reinforcements. Test results indicate that both types of reinforcements substantially improve the performance of the stiff clay foundation bed. A maximum threefold improvement was observed in bearing pressure, depending on the reinforcement type. However, geocell was found to be the most advantageous soil reinforcement technique, giving maximum performance improvement.

Utilization of Sustainable Materials for Soil Stabilization: State-of-the-Art

Abstract: Most of the challenging soil deposits necessitate their stabilization either by adopting mechanical modification, which includes soil replacement, compaction, surcharge loading and piling or chemical alteration by using lime, cement, and chemical additives. These methods of stabilization are oriented towards improving certain defined properties such as plasticity, swell potential, strength, and density of the soil mass. Besides, one of the most crucial challenges that is faced is “stabilization induced cracking of the fine-grained soils,” which turns out to be the basic reason for the failure of the soil mass and subsequent failure of the structures. However, concerns such as non-availability of the ideal soil for replacement of the native soil and even inaccessibility of the site and laborious soil-stabilizer mixing methods necessitate exploring suitable alternatives for stabilization of such soil deposits that adds up to the vows of the practicing engineers. A few other pressing issues which need to be addressed are the adverse effects caused by these additives on the environment (viz., release of greenhouse gases and/or subsequent leaching of chemicals into the ground water). In such a scenario, application of industrial by products (viz., fly ash, cement kiln dust, blast furnace slag, rice husk ash, silica fumes, red mud, and textile waste), which could be defined as “sustainable materials,” find a special place in the modern-day soil stabilization and modification exercise. Keeping this in view, a critical synthesis of the literature has been presented in this paper, which showcases superiority of the sustainable materials over the conventionally used soil stabilizers and the need for conducting further research to make these materials an easy and choicest replacement over the former.

Soil Conditioning for EPB Shield Tunneling in Argillaceous Siltstone with High Content of Clay Minerals: Case Study

Abstract: Soil clogging occurred in the early construction stage of Nanchang Metro Line 1, China, when an earth balance pressure (EPB) shield passed through the argillaceous siltstone with a total content of clay minerals of 40.5%. This paper presents a new scheme for determining soil conditioning parameters to avoid the occurrence of soil clogging, taking both the slump value and the liquidity index of the soil into account. As indicated by the results of slump tests, the optimum slump value for the soil conditioning ranged from 17 to 20 cm, and a fitting function of slump value against foam injection ratio (FIR) and water content (w) was obtained. Considering the requirement for a liquidity index equal to ∼0.4–0.75 to ensure the stability of the excavation face, a chart was proposed for the soil conditioning. Based on the chart, the optimum FIR and w for the soil conditioning for tunneling in argillaceous siltstone were determined to be ∼19.2–23.2% and ∼14.2–36.6%, respectively. Taking shield parameters, ...

Effect of Natural Zeolite and Cement Additive on the Strength of Sand

Abstract: It is widely known and well emphasized that the cemented sand is one of economic and environmental topics in soil stabilization. In some instances, a blend of sand, cement and other materials such as fiber, glass, nano particle and zeolite can commercially be available and effectively used in soil stabilization especially in road construction. In regard to zeolite, its influence and effectiveness on the properties of cemented sands systems has not been completely explored. Hence, in this study, based on an experimental program, it has been tried to investigate the potential of a zeolite stabilizer known as additive material to improve the properties of cemented sands. A total number of 216 unconfined compression tests were carried out on cured samples in 7, 28 and 90 days. Results show unconfined compression strength and failure properties improvements of cement sand specimens when cement replaced by zeolite at optimum proportions of 30 % after 28 days due to pozzolanic reaction. The rate of strength improvement is approximately 20–78 and 20–60 % for 28 and 90 days curing times respectively. The efficiency of using zeolite has been enhanced by increasing the cement content and porosity of the compacted mixture. The replacement of cement by natural zeolite led to an increase of the pH after 14 days. Chemical oxygen demand (COD) tests demonstrate that the materials with the zeolite mixture reveal stronger adsorptive capacity of COD in compare to cemented mixture. Scanning electron microscope images show that adding zeolite in cemented sand changes the microstructure (filling large porosity and pozzolanic reaction) that results in increasing strength.

Plasticity, strength, permeability and compressibility characteristics of black cotton soil stabilized with precipitated silica

Abstract: The suitability of using precipitated silica (PS) from the burning of rice husk was investigated to improve the geotechnical engineering properties of a black cotton soil. A laboratory experimental program consisting of series of specific gravity, Atterberg limits, compaction, California bearing ratio (CBR), unconfined compression and consolidation tests was conducted on the untreated and PS treated soil samples. The application of PS to the soil significantly changed its properties by reducing its plasticity and making it more workable, improving its soaked strength, and increasing its permeability and the rate at which the soil gets consolidated. An optimal PS content of 50%, which provided the highest soaked strength, is recommended for the improvement of the subgrade characteristics of the BC soil for use as a pavement layer material.

Potentials of rice husk ash for soil stabilization

Abstract: Due to the large production of agricultural wastes, the world is facing a serious problem of its handling and disposal. The disposal of agricultural wastes has a potential negative impact on the environment causing air pollution, water pollution and finally affecting the local ecosystems. So it is mandatory to make these agricultural wastes ecofriendly. By using them as soil stabilizers, these agricultural wastes improves the strength of soil and its characteristics without causing any harm to the environment. The objective of this paper is to upgrade soil as a construction material using rice husk ash (RHA) which is a waste material. The cost of construction of stabilized road have been keeping financially high due to the over dependency on the utilization of industrially manufactured soil improving additives (cement, lime etc.). By using the agricultural waste (such as rice husk ash RHA) the cost of construction will be considerably reduced as well reducing the environmental hazards they cause. The performance of the soil-RHA was investigated with respect to compaction characteristics, unconfined compressive strength (UCS) and California bearing ratio (CBR) tests. The results obtained, indicates a considerable decrease in the maximum dry density (MDD), an increase in optimum moisture content (OMC) and a superficial improvement in the CBR and UCS values with the increase in the RHA content. The peak UCS values were recorded at between 6-8% RHA, which indicated that a little potential of using 68% RHA shows a considerable improvement in the strength characteristics of the soil.

Use of nanoscale zero-valent iron and nanoscale hydrated lime to improve geotechnical properties of gas oil contaminated clay: a comparative study

Abstract: Soil stabilization using lime has been long used to improve geotechnical characteristics of soil for civil engineering purposes. Unlike lime, as far as known to the authors, there is no specific research for soil improvement by zero-valent iron. In this study nanoscale zero-valent iron (NZVI) particles and nanoscale hydrated lime (NHL) have been used to determine their effects on Atterberg limits, compaction properties, unconfined compressive strength (UCS) and shear strength parameters (c and ϕ) of a gas oil contaminated clay soil. To determine the optimal reaction time and NZVI dosage, percent of total organic carbon in the contaminated soil with 9 % of gas oil was measured. From experimental data, optimum reaction time and NZVI dosage were 24 days and 5 %, respectively. Then, the contaminated samples were prepared by mixing the soil with gas oil in amounts of 0, 3, 6 and 9 % by dry weight. The results showed a decrease in UCS, maximum dry density, optimum moisture content and internal friction angle and an increase in liquid limit (LL), plastic limit (PL) and cohesion. Finally, all contaminated specimens were mixed with 5 % of NZVI. After 24 days an increase in UCS, maximum dry density, optimum water content and shear strength parameters was seen. In addition, a decrease in LL and PL was observed. On the other hand, adding 5 % of NHL to the contaminated soil increased UCS, shear strength parameters, LL, PL, optimum moisture content and decreased plasticity index and maximum dry density of the soil after 24 days.

Improving Geotechnical Characteristics of Kaolin Soil Using Silica Fume and Lime

Abstract: Soil stabilization, as a cost-effective and environmentally friendly method, is used in the building of systems such as roads, dams, and river levels. Chemical stabilization of soil is carried out by adding binder or by-products such as lime (L) and silica fume (SF) to the soil, thereby modifying the geotechnical performance of thre soil. This type of soil can be categorized as problematic due to its weak properties. At the preliminary stage, soft clay soil does not meet the requirements necessary for construction purposes because the entire load from the top of the building will be transferred to the underlying soil. This research considered the soil stabilization of a soft clay soil (Kaolin S300) stabilized with various percentages of lime and 4% SF. The percentage of lime varied at 3%, 5%, 7%, and 9%, while the percentage of SF was fixed at 4%. The main objective in this research was to improve the undrained shear strength of soft clay soil mixed with various percentages of lime and also 4% SF. The focus of the study was on determining the physical properties of the soils tested and the consolidation of kaolin mixed with 4% SF and different percentages of lime. The results showed that the optimum L-SF percentage with respect to the maximum shear strength occurred at 5%. The soilL-SF mix increased the shear strength and angle of internal friction compared to the soil-L and soil-SF mixes because the pozzolanic reaction between lime and SF was more effective with soil particles. The optimum percentages for enhancing the shear strength and the angle of friction were 7% and 4% for lime and SF, respectively. Microstructural development took place in the stabilized soil due to an increase in the lime content of tertiary clay stabilized with the L-SF mix.

Impact of Lime, Cement, and Clay Treatments on the Internal Erosion of Compacted Soils

Abstract: The aim of this paper is to study the impact of certain soil treatments on the internal erosion characteristics of treated compacted silt. The experiments measured the internal erosion using the hole erosion test (HET). This study aims to describe the effects of clay, lime and cement soil treatments on the internal erosion, specifically with regard to the amount of treatment used and the curing time. A new enhanced HET was developed to apply a high inlet pressure up to 650 kPa and thus generate a hydraulic shear stress up to 10,000 Pa. The internal erosion resistance was quantified by the coefficient of soil erosion and the critical shear stress. The results demonstrated that clay treatment could reduce the coefficient of soil erosion depending on the nature and percentage of clay added to the soil. The results also showed that lime and cement treatment primarily increased the critical shear stress of the tested silt. This increase was higher with cement treatment and was dependent on the amount o...

Stabilization of Quarry Fines Using a Polymeric Additive and Portland Cement

Abstract: The effect of treating limestone quarry fines (LQFs) with a commercially available liquid polymeric soil stabilizer, and a combination of the polymeric soil stabilizer and a small quantity (4%) of portland cement was evaluated. The research reported in this paper, which consisted of tests on both treated and untreated mixes, with the aim of evaluating the use of LQF in pavement construction was comprised of the following tests: (1) compaction, (2) unconfined compressive strength, (3) static flexural strength, and (4) durability. Test results showed marked improvements in the optimum moisture content, unconfined compressive strength, and static flexural strength, and no improvement in maximum dry density when polymer or both polymer and cement were added. Improvements in unconfined compressive strength were above the U.S. national requirements for admixtures for soil stabilization. Polymer-treated specimens were more susceptible to moisture than specimens treated with portland cement (PC) alone, an...

Soil stabilization using plastic waste

Abstract: Soil is the key element of this nature and all the basic needs of life such as food, house and cloths are fulfilled by the soil. Black Cotton soils with high potential for swelling and shrinking as a result of change in moisture content are one of the major soil deposits of India. Soil stabilization is the process which improves the physical properties of soil, such as shear strength, bearing capacity which can be done by use of controlled compaction or addition of suitable admixtures like cement, lime, sand, fly ash or by providing geo textiles, geo synthetics etc. The new technique of soil stabilization can be effectively used to meet the challenges of society, to reduce the quantities of waste, producing useful material from non-useful waste materials. Since the use of plastic in diversified forms such as chairs, bottles, polythene bags, etc., has been advancing speedily and its disposal has been a problem all the time regarding the environmental concern, using plastic as soil stabilizer would reduce the problem of disposing the plastic as well as increases the density and California Bearing Ratio (CBR) of soil in an economical way. The present study is focused to overcome the problems experienced in Amaravathi, the capital of newly formed Andhra Pradesh State. In the present study, an experimental program was conducted for stabilization of Black Cotton Soils in the Capital Region i.e., Amaravathi of newly formed Andhra Pradesh, with the utilization of Plastic waste as soil stabilizer. Different contents of plastic strips (% by weight varying from 0% to 8%) are added to the Black Cotton Soil and the optimum percentage of plastic strips in soil was found out by conducting California Bearing Ratio Test.

Geometric models for lateritic soil stabilized with cement and bagasse ash

Abstract: Agricultural and environmental demands for natural aggregates coupled with frequent increases in the price of cement and other binders have consequently escalated the cost of construction, rehabilitation and maintenance of road works. Soil stabilization emerges as an attractive option for providing low-cost roads. Bagasse-ash is an agricultural material obtained after squeezing out the sweet juice in sugarcane and incinerating the fibrous residue to ash. This residue that would have constituted an environmental problem during disposal and handling could be used as a supplement or partial replacement for cement in the cement-bound soil when converted to ash. Thus this study attempted to investigate into the effects of bagasse ash on compaction and strength characteristics of cement-stabilized lateritic soil and also to develop geometric models. The compaction, California bearing ratio, unconfined compressive strength and durability tests were carried out on the cement-stabilized soil. Constant cement contents of 2%, 4%, 6% and 8% with variations of bagasse ash from 0% to 20% at 2% intervals and all percentages used were by the weight of dry soil. The multiple regression and the least square approach was used to develop geometric equations which was made less rigorous with Minitab statistical software. The three geometric equations developed covered the relationships of cost of bagasse ash content, optimum moisture content, cement content, California bearing ratio and unconfined compressive strength at 7 days. It was observed that optimum moisture content increased progressively while maximum dry density reduced with increase in bagasse ash content. Also the increase in cement content increased both the optimum moisture content and maximum dry density. In addition, all the strength properties were increased with increase in bagasse ash content and chemistry responsible was also presented. Thus bagasse ash was confirmed to be a good admixture in soil stabilization for road-work. The models were calibrated and verified; and were found to be dependable. http://dx.doi.org/10.4314/njt.v35i4.11

Role of Sodium Silicate Additive in Cement-Treated Kuttanad Soil

Abstract: This study aims at understanding various parameters that influence the performance of the sodium silicate (SS) additive along with cement in treating the soft Kuttanad soil. The change in soil structure in the presence of SS additive during cement treatment has been correlated with the engineering properties of cement-treated Kuttanad soil. The unconfined compressive strength (UCS) of samples was measured to study the additive dosage effect and to evaluate the impact of the clay water to cement (W/C) ratio on the additive performance. Microstructural and mineralogical investigations were carried out using X-ray diffraction (XRD) studies, scanning electron microscopy (SEM), pH, and zeta potential measurements. The results show that the presence of SS additive notably impacts the strength behavior of Kuttanad soil treated with cement by more than one mechanism. SS additive accelerates and augments the formation of calcium silicate hydrate (CSH). Further, it is found to induce changes in fabric and pore water chemistry that favor enhanced cementation imparting substantial strength to the cemented soil matrix. (C) 2016 American Society of Civil Engineers.

Bearing Capacity Improvement of Shallow Foundations Using Cement-Stabilized Sand

Abstract: In order to attain a satisfactory level of safety and stability in the construction of structures on weak soil, one of the best solutions can be soil improvement. The addition of a certain percentage of some materials to the soil may compensate for its deficiency. Cement is a suitable material to be used for stabilization and modification of a wide variety of soils. By using this material, the engineering properties of soil can be improved. In this study, the effect of soil stabilization with cement on the bearing capacity of a shallow foundation was studied by employing finite element method. The material properties were obtained by conducting experimental tests on cement-stabilized sand. Cement varying from 2% to 8% by soil dry weight was added for stabilization. The effect of reinforced soil block dimensions, foundation width and cement content were investigated. From the results, it can be figured out that by stabilizing the soil below the foundation to certain dimensions with the necessary cement content, the bearing capacity of the foundation will increase to an acceptable level.

Effect of Fly Ash and Rice Husk Ash on Permanent Deformation Behaviour of Subgrade Soil under Cyclic Triaxial Loading

Abstract: This work presents the laboratory study conducted on fly ash and rice husk ash as soil stabilizers. Using these stabilizers, the deformation behaviors of subgrade soil-mixtures under repeated triaxial loading was conducted. Resilient strain, permanent strain and resilient modulus were ascertained at different deviator stress level and confining pressures at constant moisture content. Admixing of fly ash and rice husk ash reduces the maximum dry density but increase the water demands. The variations of elastic deformation and resilient modulus were significantly influenced by fly ash and rice husk ash contents. Better performances were observed for admixed soil irrespective of number of load applications. The results obtained from the laboratory confirm the potential use of subgrade soil admixed with fly ash and rice husk ash with respect to the permanent deformation.