Engineering Properties Of Clayey Soil Research Articles

Compressibility behavior of colemanite added bentonite under short and long-term high temperature

Introduction
 The increasing energy demand and the limited fossil fuel resources make searching for new sustainable clean energy sources. In this regard, it is vital to use energy geo-structures as a renewable and clean energy source. The geo-structures are in direct contact with the soil and cause temperature changes throughout the soil mass.
 Bentonite is considered suitable as an engineering barrier in deep geological disposal repositories for spent nuclear fuel, mainly because of its favorable swelling properties and extremely low permeability [1]. It was reported by many researchers that the engineering properties of clayey soils change at high temperatures [2,3]. Therefore, there is a need for soil materials that can maintain their long-term engineering properties under high temperatures. Borates are naturally occurring minerals. They can be found mainly in sediments and sedimentary rocks. The most commercially important boron minerals are tincalconite, colemanite, and ulexite [4].
 In the present study, it was tried to improve the compressibility behavior of bentonite by adding colemanite under high temperature. The oedometer tests were performed under a constant temperature (80 ºC) on the bentonite-colemanite mixtures. In this context, samples exposed to short and long-term high temperature (80 ºC) were used and the results were compared with the room temperature results.
 Material Characterization and Methods
 The Ca-bentonite sample used which is activated with sodium bicarbonate. Colemanite was added to bentonite at a rate of 10% of the bentonite by dry weight. In this context, B10C sample represents a 10% colemanite added bentonite mixture. The liquid limits of bentonite and colemanite are 270% and 37%, respectively. The samples (smaller than 75 μm) were obtained by mixing the mixture powder with tap water at a water content of 1.5 times the pre-determined liquid limit value of the mixtures. The slurries were consolidated under a vertical pressure of 12.5 kPa for 14 days. Samples 70 mm in diameter and 19 mm in height were obtained by trimming. The samples were placed in oedometers for tests at room and high temperature (80 ºC). The experimental system was modified for high-temperature tests. The modified system consists of a conventional apparatus, a heat ring, a thermostat, and a water tank. Thus, by heating the cell water, the temperature of the sample was indirectly increased to 80 °C. For long-term experiments, samples were placed in thermal pools in clamped molds (constant volume). These molds were kept in the thermal pools under a constant temperature of 80 °C for 6 months. Then, the consolidation tests of these samples were performed at 80 °C.
 Results and Discussions
 The result of the consolidation tests of bentonite mixtures at 80 °C after being kept in the thermal pool for 6 months is given in Figure 1. For comparison, the test results at room temperature and 80 °C are also shown. The compression amount of bentonite increased with the increase in temperature, while the swelling amount decreased. The total compression deformation of the bentonite sample, which showed 53% compression at room temperature, reached 65% when the temperature was increased to 80 °C. However, swelling deformation decreased from 7% to 3% when the temperature was increased. When the volumetric deformation behavior of bentonite (NC) is examined, thermal contraction behavior at high temperature (90 °C) was reported [2]. In other words, the vertical compression amount of NC bentonite increases at elevated temperatures. In addition, since the structure of the clay deteriorated at high temperature and the deformations were permanent, it was an expected result that the rebound (swelling) behavior would decrease at high temperature.
 There was a decrease in the amount of compression in the sample cured for 6 months, compared to 80 °C. However, although the compression amount of the 6-month cured sample decreased, the amount of compression still slightly increased compared to the room temperature. Compression-swelling deformation amounts of the samples cured for 6 months and tested at 80 °C are presented in Table 1 in detail. When the swelling behavior of additive-free bentonite was examined, increasing temperature decreased the rebound behavior of bentonite. In addition, the swelling amount of the sample cured for 6 months was determined to be almost the same as the sample at 80 °C. The reason for this was that the deformations that occurred at high temperatures were permanent. 
 When the temperature of the colemanite-added bentonite mixtures was increased, the amount of deformation increased. However, the amount of deformation of additive-free bentonite decreased with the colemanite addition at 80 °C, and returned to its room temperature value (approximately 53%). In other words, the addition of colemanite had a positive effect by reducing the deformation amount of bentonite at both short and long term high temperatures. The short and long term effects of 80 °C temperature on colemanite added samples were almost the same.

Use of Egg Shell Powder and Periwinkle Shell Ash to Strengthen the Engineering Properties of Clayey Soil

Recently, the stabilization of clayey soil (CS) has drawn the attention of numerous researchers. In the past, Egg Shell Powder (ESP) and Periwinkle Shell Ash (PSA) were individually tested for their ability to stabilize clayey soil. The author has attempted to stabilize the clayey soil by combining the two of them. The goal of the current study was to compare the efficacy of various eggshell powder and periwinkle shell ash concentrations as soil stabilizers. Testing procedures include the California Bearing Ratio (CBR), Atterberg limits, Unconfined Compression Test (UCS), and compaction tests on the mixture of clayey soil, eggshell powder and periwinkle shell ash. In this study, ESP and PSA were used as soil stabilizers. PSA was varied (i.e., 3%, 6%, 9%, 12%) after ESP was fixed at 12% utilizing index properties testing. The current study aims to evaluate the increase in the strength and stability qualities in soft subgrade soil by stabilizing it first with ESP and then reinforcing it with PSA. It was found that curing time, eggshell powder, and periwinkle shell ash concentration all significantly affected the engineering qualities of the stabilized soil. The findings demonstrated that increasing eggshell powder content increased unconfined compression strength and California bearing ratio values up to a certain point and then decreased slightly. On the other hand, the strength attributes described increased as periwinkle shell ash concentration increased. Additionally, it was found that the stabilized soil samples' strength properties had been significantly improved by the curing period. Key Words: Atterberg limits, CBR, Compaction test, Eggshell Powder, Periwinkle Shell Ash

Characteristics of Clayey Soil for the Subggrade of Flexible Pavement

Clayey soil is typically firm when they are evaporated and gave its firmness as it looks right on soaked. Delicate clays are related with little compressive strength and beyond preposterous arrangement. This decrease in strength because of dampness prompts serious harm to the structures and substructures. The nature of the soil can experiment with the originator fabricating foundation intent on clayey sediments. This paper is based on the study of the engineering properties of clayey soil. This experimental study depicts the basic attributes of the clayey soil; which further leads to improving the nature or engineering properties of the clayey soil for the subgrade of the flexible pavement. Different tests are to be performed in the laboratory and conduct the desired results.

Effect of low-density polyethylene, polyvinyl chloride, and high-density polyethylene micro-plastic contamination on the index and engineering properties of clayey soil- an experimental study

Soil health is one of the prominent features of the Sustainable Development Goals (SDGs). The SDGs seek to achieve the target of 75% healthy soils by 2030. On the contrary, the growing accumulation of microplastic contamination in soil environments is an issue of worldwide concern. The effect of a variety of microplastic accumulation on soil index and engineering properties is still unclear. Clayey soil is very important in geotechnical engineering because of its complex behaviour. This study investigates the effects of a variety of microplastics such as Low-Density Polyethylene (LDPE), Polyvinyl Chloride (PVC), and High-Density Polyethylene (HDPE) in environmental relevant concentrations (2%,4%,6% w/w) on index and engineering properties of clayey soil with respect to a number of observation days. In the present study, the non-contaminated soil treated as a control. The detailed experimentation revealed a significant change in the liquid limit, plastic limit, and shear strength values of clayey soil with an increasing percentage of microplastic contamination, whereas minute changes are recorded with respect to the number of observation days, this may be due to inert nature of microplastic. The shear strength is one of the critical engineering properties of soil that determines the strength and stability of the soil. The shear strength value of 0.94 kg/cm2 for control decreased to 0.76 kg/cm2 and 0.73 kg/cm2 and 0.85 kg/cm2 for the addition of 2%, 4%, and 6% respectively of LDPE microplastic contamination, similarly, for PVC microplastic contamination of 2%, 4% the shear strength decreases to 0.77 kg/cm2, 0.85 kg/cm2 respectively, the HDPE microplastic contamination of 2%, 4%, and 6% results in shear strength decrease to 0.52 kg/cm2, 0.53 kg/cm2 and 0.65 kg/cm2.The altered values of shear strength along with other index and engineering properties of soil due to microplastic contamination may lead to instability in structures or may increase the chances of harmful natural threats such as landslides. The present study provides evidence of significant changes in the index and engineering properties and therefore the stability of the soil which is the major contribution of the study.

Effect of organic matter on the shear strength of lime-stabilised clayey soils

Soils containing organic matter exhibit low shear strength and high compressibility. Lime stabilisation has been shown to improve the engineering properties of clayey soils. An attempt was made to study the effect of organic matter (starch and peat) on the shear strength of lime-stabilised clayey soils subjected to longer curing periods (up to 180 days). Most studies have reported the strength behaviour of lime-stabilised organic soils up to 60 days. Vane shear tests were carried out on artificially prepared organic soil mixtures treated with 6% lime after different curing periods (0, 7, 30, 60, 90 and 180 days). The results indicate that the improving effect of lime is deteriorated in the presence of organic matter as the curing period increases. It was observed that, for lime-stabilised clayey soils containing organic matter, the strength seemed to increase up to 30 days, after which it ceased. The strength reduction in lime-stabilised clayey soils containing organic matter depended on the pH and functional groups present in the soil. Fourier transform infrared spectroscopy of cured samples was also carried out to examine the microstructural changes responsible for the strength change in lime-stabilised clayey soils.

Effects of compaction state on desiccation cracking behaviour of a clayey soil subjected to wetting-drying cycles

Desiccation crack is an important factor affecting engineering properties of clayey soils. In this study, the effects of compaction state and wetting-drying cycles on desiccation cracking behaviour of a clayey soil were investigated. Nine samples with various compaction water contents and dry densities were subjected to three wetting-drying cycles and the evolution of desiccation cracks was quantitatively described. The results reveal that both compaction water content and dry density play an important role in the development of desiccation cracks. Specifically, for the samples compacted on the dry side, desiccation cracks develop simultaneously. This phenomenon is also observed in samples compacted on the wet side with low densities. However, for the samples compacted on the wet side with high dry densities, desiccation cracks develop sequentially. Moreover, the higher the compaction water content, the faster development of desiccation cracks, and the smaller surface crack ratio, total crack length and average crack width. The higher the dry density, the slower development of desiccation cracks, and the smaller surface crack ratio and total crack length. Furthermore, the development of desiccation cracks can be divided into two stages according to the evolution of crack propagation velocity: (a) crack length extension, where total crack length increases rapidly with little changes in average crack width, and (b) crack width widening, where total crack length no longer changes and average crack width increases until it stabilizes. In addition, surface crack ratio, total crack length and average crack width all show an upward trend as wetting-drying cycles progresses. This tendency is more pronounced in the soil sample with a higher compaction water content and a larger dry density.

Engineering Properties and Slope Inventory of Clayey Soil from the Trusmadi Formation in Bundu Tuhan, Sabah

The study area in Bundu Tuhan mainly consists of the metasedimentary rock of the Trusmadi Formation. Trusmadi Formation aged Palaeocene to Middle Eocene made up of interbedded dark grey shale and thin sandstone that shows the characteristics of deep marine sediment. Shale bed also known as phyllite unit is the major rock unit in Trusmadi Formation that is usually weathered and produced clayey soil. Clayey soil is often acknowledged as problematic soil due to its properties that tend to hold water highly compared to sandy soil, which will cause further engineering problems due to the soil creeping. The study area is prone to landslide activity, especially in the Trusmadi Formation’s slopes. Hence, this paper aims to determine the engineering properties of clayey soil from the Trusmadi Formation. Two slopes were also selected for laboratory analysis and slope inventory. The results of the analysis show that both samples are poorly sorted materials which are classified as sandy and silty clay soil and silty clay soil. The moisture content is 25.98% to 37.10%, specific gravity ranged from 2.52 to 2.57, and plasticity index ranged from 21.68% to 23.91%. The soil has inactive to a normal type of clay (0.59 to 0.97) with a very high swelling capacity (9.29% to 11.43%). The maximum dry density (MDD) ranged from 1.44 to 1.53 and optimum moisture content (OMC) of 25.47% to 25.67%. Also, both samples are classified as impermeable soil with a K value ranging from 1.74x10−8 m/s to 2.45x10−8 m/s. While, based on the slope inventory inspection, both slopes were comprised of metagreywacke, where the first slope was an embankment slope, and the second slope was a cut slope. The first slope has poor vegetation cover which leads to moderate erosion and instability that further caused failure which is rotational debris slide. As for the second slope with average vegetation cover, there is only minor erosion and instability present on the slope, and this slope also shows slow soil movement that indicates soil creep.

Freeze-Thaw Behavior of Stabilized Clayey Soil with Red Mud and Cement

The clayey soils in areas with seasonal frost are exposed to at least one freeze-thaw cycle every year and worsen their engineering properties. To prevent the engineering properties of clayey soils, it is necessary to improve the freeze-thaw resistance of them. In this study, the clayey soil was stabilized by using red mud and cement additive materials. Prepared samples of clayey soil and stabilized clayey soil were subjected to the unconfined compressive test. To investigate the effects of red mud and cement additive materials on the freeze-thaw resistance of clayey soil, the natural and stabilized expansive soil samples were exposed to the freeze-thaw cycles under laboratory conditions. The obtained results showed that the red mud and cement additive materials increased the freeze-thaw resistance of clayey soil. Consequently, it was concluded that red mud and cement additive materials can be successfully used to improve the freeze-thaw resistance of clayey soils.

Investigating the effect of PET plastic bottle strips on the strength and compressibility properties of clayey soil

The production of plastic bottles by the manufacturing industry has increased drastically over the last six decades across the globe. This rapid production has led to the generation of many waste plastic bottles, thus causing environmental pollution. About 180 tonnes of plastics are generated daily in Kampala, the capital city of Uganda, and around 50% is dumped into the Kiteezi landfill. Instead of putting pressure on the landfill, these plastic bottle wastes could be reused in stabilizing soils with poor engineering properties. The current study investigates the engineering properties of clayey soil reinforced with Polyethylene-terephthalate waste plastic bottle strips. In order to achieve the objectives of the study, the geotechnical and engineering properties of the soil reinforced with waste plastic bottle strips at 0.1, 0.2, 0.3 and 0.4% of the dry unit weight of the soil and non-stabilized soil were determined by conducting laboratory tests, such as particle size distribution, Atterberg limits, compaction test and California Bearing Ratio. The results revealed that the California Bearing Ratio of the soil reinforced with Polyethylene-terephthalate waste plastic bottle strips increased with the increase in the percentage of Polyethylene-terephthalate waste plastic bottle strips up to 0.3%. Beyond 0.3%, a drop in California Bearing Ratio was observed. It indicates that 0.3% Polyethylene-terephthalate waste plastic bottle strips is the optimum percentage for stabilizing low plasticity clayey soils.

Effect of Expanded Polystyrene Particle Size on Engineering Properties of Clayey Soil

The particle size of expanded polystyrene (EPS) has an effect on engineering properties of EPS-clay blends. However, the effect of differences between EPS particle size groups subdivided within 1–3 mm on engineering properties is usually ignored. In this study, different particle sizes of EPS pellets have been considered to separately investigate the effect on the optimum water content (OWC), maximum dry density (MDD), unconfined compressive strength (UCS), ductility, coefficient of permeability, and compression index of EPS-clay blends. Results show that the MDD, ductility, hydraulic conductivity, and compression index of EPS-clay blends do not increase with the increase in the EPS particle size in the range of 0.3–3 mm, while the OWC and UCS do not decrease. For a given EPS content, among samples with the EPS particle size of 0.3–1 mm, 1-2 mm, and 2-3 mm, the MDD and UCS of EPS-clay blends with 1-2 mm in EPS particle size are the largest, while the OWC, ductility, coefficient of permeability, and compression index are the smallest. Microstructure analyses reveal that, for samples with the EPS particle size of 1-2 mm, the pore volume is lower and the microstructure is denser, which are the main reasons why the EPS particle size can influence engineering properties of EPS-clay blends.

Impact of Silica on Geotechnical Properties of Clayey Soil Present in Edfu- Aswan, Egypt

It may be necessary to improve the engineering properties of clayey soils to make them suitable for construction by using some kind of stabilization methods. Treatment with lime, cement or waste materials such as silica fume (SF) has traditionally been used for the stabilization of clayey soils. The soil chosen in this research was extracted from a site in Edfu- Aswan, Egypt. Investigating the effect of properties of cohesive soils when mixed with SF is the main objective of this study. Silica fume is a mineral made up of ultra-fine solid, amorphous silicon dioxide glass spheres (SiO2) from the metallurgical industries company (E.JS.C) in Edfu. A series of laboratory experiments for samples prepared with different percentages were implemented of SF 0%, 2%, 4%, 6%,8%, and 10%. The results show that the blend will increase the maximum dry density of clayey soils. Their Plasticity Index and the liquid limit would increase, the permeability of clayey soil decreases, the unconfined compression strength will increase. All of these results can be summarized to say that the engineering properties of cohesive soils can be improved by combining Silica Fume and clayey soils together.

Evaluating the Durability of Lime-Stabilized Soil Mixtures using Soil Mineralogy and Computational Geochemistry

Lime stabilization is a common technique used to improve the engineering properties of clayey soils. The process of lime stabilization can be split into two parts. First, the mobilization and crowding of [Formula: see text] ions or [Formula: see text]molecules from hydrated lime at net negative surface charge sites on expansive clay colloids. Second, the formation of pozzolanic products including calcium-silicate-hydrate (C-S-H) because of reactions within lime-soil mixtures. The pozzolanic reaction is generally considered to be more durable, while the [Formula: see text] adsorption has been associated with more easily reversible consistency changes. This study offers a protocol to assess whether the stabilization process is dominated by durable C-S-H (pozzolanic) reactions or a combination of cation exchange and pozzolanic reactions. Expansive clays with plasticity indices >45% from a major highway project in Texas are the focus of lime treatment in this study. The protocol consists of subjecting lime-soil mixtures to a reasonable curing period followed by a rigorous but realistic durability test and investigating the quality and quantity of the pozzolanic reaction product. Mineralogical analyses using quantitative X-ray diffraction (XRD) and thermogravimetric analysis (TGA) indicates the formation of different forms of C-S-H. In addition, geochemical modeling is used to simulate the lime-soil reactions and evaluate the effect of pH on the stability of C-S-H. The results indicate C-S-H with Ca/Si ratio of 0.66 as most the stable form of C-S-H among other forms with Ca/Si ratio ranging from 0.66 to 2.25. The effect of reducing equilibrium pH on C-S-H is also evaluated. A reduction in pH favored dissolution of all forms of C-S-H indicating the need to maintain a pH ≥ 10.

An Improved Predictive Model for Determining the Permeability Coefficient of Artificial Clayey Soil Based on Double T2 Cut-Offs

Permeability is one of the most important engineering properties of clayey soil. However, the traditional method for determining the permeability coefficient is time-consuming. To establish a simple and accurate predictive method to obtain the permeability coefficient of artificial clayey soil based on the double cut-off transverse relaxation times (T2 cut-offs) using low-field nuclear magnetic resonance (NMR) technology, eight kinds of artificial clayey soil with different mineralogical compositions were prepared in the laboratory. Evaporation tests at 40°C were carried out on the saturated artificial clayey soil samples in an oven. During the evaporation process, NMR tests were also performed on the artificial clayey soil every hour. The results showed that the evaporation process could be divided into three stages according to different evaporation rates: the constant rate stage (CRS), the falling rate stage (FRS), and the residual stage (RS). The water evaporated in the CRS and FRS was defined as the absolute movable water and the partially movable water, respectively. The water that could not evaporate in the RS was defined as the immovable water. Based on the cumulative signal amplitudes in the T2 spectrum corresponding to different kinds of water, the double T2 cut-offs were defined. On the basis of the double T2 cut-offs and T2 spectrum of the saturated sample, an improved Timur–Coates (TC) model was established. The prediction capability of the improved model was evaluated by finding the determination coefficient (R2), mean absolute error (MAE), and root-mean-square error (RMSE). Compared with the typical TC model, the prediction accuracy of the improved model was much higher. In addition, the relationships between the double T2 cut-offs and fractal dimension (D) of the T2 spectrum of saturated artificial clayey soil were also identified.

Effect of gypsum content on unsaturated engineering properties of clayey soil

Many of gypsum soils have existed in arid and semi-arid lands. It is considered one of the most problematic soils because of its complicated and unpredicted behavior when exposure to moisture. Extensive researches have been conducted in Iraq to observe the behavior of such soil and to suggest safety restrictions for the collapse and set practical precautions for the structures. This study investigated the effect of gypsum content on some unsaturated engineering properties of a clayey soil. Three different proportions of gypsum (0%, 5% and 20% by weight of the parent soil) were added and tested. The samples have been subjected to swelling potential test, soil water retention curve (SWRC), vapour diffusion and shear strength parameters. It is observed that gypsum content has a significant influence on SWRC, whereas, soil that has high gypsum content made SWRC with higher variables represented by air entry values and residual state. On the other hand, an increase in gypsum content led to a reduction of swelling potential and shear strength parameters. The results of vapour diffusion indicate that gypsum content could modify the microstructure in an unsaturated state and reduce the vapour diffusion through the soil. Â

Improvement in the Engineering Properties of Clayey Soil Using Sodium Chloride

Major problem faced by civil engineers is when an available site does not have suitable engineering properties to support structures, roads and foundation. The soil of the site may be weak due to number of reasons. A difficult problem in work exists when the soil is found to be clay or the water table in that region is high. Soils with high clay content generally have low shear strength and has tendency to swell when their moisture content is allowed to increase. For these reasons clayey soil is not suited for structures, roads and foundation. Engineering properties of clayey soil can be improved by adopting different methods of soil stabilization. Many stabilization methods are in practice for altering the engineering properties of the clayey soil. Common methods for stabilization of clayey soil are lime and cement stabilization. Soil can also be stabilized by chemical stabilization. Sodium Chloride is the ionic compound of sodium and chloride. A recent study shows that Sodium Chloride can be effectively dissolves in water quickly and provide enough sodium ions for exchange ionic reactions with clayey soil. Function of this chemical (sodium chloride) is to form into cluster of fine particles and bind them together. Sodium chloride dosage is added in 0.5% to 3.0% by weight of soil with 0.5% of increment in each dosage. Standard proctor test, California Bearing Ratio (CBR), consistency limits test and unconfined compressive strength (UCS) test are performed to determine the optimum dosage of Sodium chloride. Tests result indicates that both unsoaked and soaked CBR value of soil increases with the increase in dosage in sodium chloride. Soaked CBR value increases from 4.75% to 9.22% and unsoaked CBR value increases from 8.72% to 13.55% of soil mixed with 2% Sodium Chloride. UCS of the soil increases from 2.75 kg/cm² to 6.33 kg/cm² upon addition of 2% Sodium Chloride. Maximum dry density of soil increases while optimum moisture content(OMC) decreases with increment in the dosage of Sodium chloride up to 2.5% and further decreases. Maximum Dry density (MDD) increases up to 9.02% that of virgin soil. Liquid limit and plastic limit of soil decreases with the addition of Sodium chloride. Liquid limit of soil decreases up to 8.3% as compared to virgin soil. Plasticity index decreases up to 10% as compared to virgin soil.

Modification of Engineering Properties of Clayey Soil by Addition of Mine Waste

The potential of using iron ore mine waste with an highly compressible clayey soil soil from North Karnataka, India, is investigated in this study. Mining activities lead to the production of waste materials during their extraction and processing stages. The waste maybe in the form of an overburden, waste Rock, Mine Water, or Tailings, depending on the geology, type of processing technology used and the resources mined. The lack of storage space has also been a major concern for the mineral producing agencies, thus paving ways for its better utilization in various construction processes. The collected mine waste was added to expansive soil in different percentages and the mix was tested for Atterberg limits, compaction characteristics, Unconfined compressive strength and California bearing Ratio. It was found that the liquid limit and plasticity index of the soil reduced with addition of mine waste while strength improved. Based on test results of maximum dry density and unconfined compressive strength, a mix of 40% mine waste with 60% expansive clayey soil is recommended for low cost roads. Blending mine waste with expansive soil paves way for sustainable construction besides economic benefits

Experimental investigation of soil reinforced with human hair fibre and chloride compounds

Many researches and advancements were carried to increase the strength of soil. Expansive soil contains montmorillonite clay mineral which is high swelling in nature. It is highly sensitive to moisture variation and it leads to encounter many engineering problems like low bearing capacity and settlement. Fibre reinforced soil is one among those advancements which offers a convenient, practical and economical method for overcoming sudden settlement and low bearing capacity. The soil can be reinforced with human hair because of its tensile property. Human Hair Fibre (HHF) is a waste material available at low cost and is not degradable in nature. Present study focuses on determining the strength characteristic of soil sample treated with human hair fibre and chloride compounds in different curing periods. Chemicals were added to the sample in varying percentage related to dry weight of the soil sample. Addition of human hair fibre and chloride compounds enhances the engineering properties of clayey soil. Chloride compounds were added at different percentages (2%, 4%, 6%, 8%, and 10%) to the soil and changes in the engineering property of soil such as penetration resistance, compaction characteristics and unconfined compressive strength of the soil were investigated. Based on present experimental study, the increase in the percentage of chloride compounds increases the dry density of the soil up to an optimum value then it decreases. The results showed that addition of HHF and chloride compounds stabilize the clayey soil to a particular extent.

Geotechnical Properties of Clayey Soils Induced by the Presence of Sodium Chloride

The presence of appreciable quantities of soluble salt indicates that engineering properties of clayey soils may change in the presence of percolating water. Hence, an attempt was made in laboratory investigation to study the geotechnical properties of clayey soils mixed with (0%, 5%, 10% and 15% by weight) of sodium chloride. Three type of clayey soils used having plasticity indices (12, 26 and 44%) were taken from three sites in Baghdad. Test Atterberg limits, unconfined compression, specific gravity, compaction and consolidation test, were conducted to investigate the effect of salt content on soil properties. The results showed that the plasticity index, optimum moisture contents, compression index, and unconfined compressive strength decrease with increasing salt content. The max dry unit weight slightly increases with increase salt content while it increases up to 5% salt then decreases for high plasticity.

Engineering properties of clayey soil stabilised with alkali-activated slag

The effects of alkali-activated slag on the engineering properties of clayey soil were investigated. The mix proportion parameters were chosen by using Taguchi's experimental design methodology. Four factors (ground-granulated blast-furnace slag content, concentration of sodium hydroxide solution, sodium hydroxide-to-sodium silicate weight ratio and alkaline solution-to-slag weight ratio) were assessed in order to obtain the greatest compaction properties, uniaxial compressive strength and California bearing ratio (CBR). Significant improvements were observed in the mechanical properties (unconfined compressive strength (UCS) and CBR) of the clayey soil with addition of the stabilisers. Optimal values (15% slag content, sodium hydroxide concentration of 6 M, sodium hydroxide-to-sodium silicate ratio of 0·5 and alkaline solution-to-slag ratio of 2·5) increased the UCS of the compound from 8 to 100 kg/cm2 at 7 d. The excessive addition of alkaline solutions weakened the strength parameters of the soil. The results showed that the most influential factor was the alkaline solution-to-slag weight ratio. The Taguchi method is an effective and suitable experimental method for optimising alkali-activated slag parameters.

Multi-scale analysis on soil improved by alkali activated binders

In the present paper, the use of alkali activated binders to improve engineering properties of clayey soils is presented as an alternative to traditional binders such as lime or cement. An alkali-activated fly ash and its chemo-physical evolution has been monitored at increasing curing times by means of X-Ray Diffraction and Scanning Electron Microscopy. Alkali-activated binder has been mixed with soil for evaluating the improvement of its mechanical behaviour. One-dimensional compression tests on treated samples have been performed with particular reference to effects induced by binder content and curing time. Test results showed a high initial reactivity of the alkali activated systems promoting formation of new mineralogical phases responsible of the mechanical improvement of the treated soil.