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The utilization of industrial by-products as stabilizers is gaining attention from the sustainability perspective. Along these lines, granite sand (GS) and calcium lignosulfonate (CLS) are used as alternatives to traditional stabilizers for cohesive soil (clay). The unsoaked California Bearing Ratio (CBR) was taken as a performance indicator (as a subgrade material for low-volume roads). A series of tests were performed by varying the dosages of GS (30%, 40%, and 50%) and CLS (0.5%, 1%, 1.5%, and 2%) for different curing periods (0, 7, and 28 days). This study revealed that the optimal dosages of granite sand (GS) are 35%, 34%, 33%, and 32% for dosages of calcium lignosulfonate (CLS) of 0.5%, 1.0%, 1.5%, and 2.0%, respectively. These values are needed to maintain a reliability index greater than or equal to 3.0 when the coefficient of variation (COV) of the minimum specified value of the CBR is 20% for a 28-day curing period. The proposed RBDO (reliability-based design optimization) presents an optimal design methodology for designing low-volume roads when GS and CLS are blended for clay soils. The optimal mix, i.e., 70% clay blended with 30% GS and 0.5% CLS (exhibiting the highest CBR value) is considered an appropriate dosage for the pavement subgrade material. Carbon footprint analysis (CFA) was performed on a typical pavement section according to Indian Road Congress recommendations. It is observed that the use of GS and CLS as stabilizers of clay reduces the carbon energy by 97.52% and 98.53% over the traditional stabilizers lime and cement at 6% and 4% dosages, respectively.

Unexpected volume changes manifested in the soil beds due to accidental release of alkalis from industrial establishments has become a major challenge. The neogenic formation that leads to volume changes due to physicochemical reactions between clay minerals and alkalis need to be addressed. The current article focusses on the possibility of using alternate by-products such as ground granulated blast furnace slag (GGBFS) and flyash (FA) for controlling the swell induced in alkali transformed kaolinitic clays, ATKC’s (i.e., red earth and kaolin). Results indicate that ATKC’s exhibited unexpected changes in swelling behavior upon inundation with water and alkali (4N NaOH) solutions. ATKC’s were later amended with FA and GGBFS to address the swelling phenomena. Marked reduction in swelling was noticed in ATKC’s with FA (10% and 20%) and GGBFS (10% and 20%). Reduction of about 40% of overall swelling was noted in alkali transformed red earth (ATR) when treated with 10% FA and 50% reduction with 10% GGBFS. Further, treatment of ATR with 20% FA and 20% GGBFS, decreased swelling to about 82% compared with ATR-4N. In case of alkali transformed kaolin (ATK), 57% and 56% reduction in swelling were observed with addition of 10% FA and 10% GGBFS, respectively. At 20% FA and GGBS content, reduction in ATK-4N swelling was 75% and 90%, respectively. Thermo Gravimetric–Differential Thermal Analysis (TG–DTA), X-ray Diffraction, and Scanning Electron Microscopy (SEM) analysis confirmed the alterations in ATKC are stabilized with FA and GGBFS.

The soils in hazardous waste sites contain heavy metals which would leach into groundwater by various biotic and abiotic processes and eventually pose a threat to human health by contaminating the drinking water. In order to understand pattern of heavy metal leachability, the field conditions can be simulated by adopting various types of sequential extraction methods. In this study, an attempt was made to evaluate the effectiveness and selectivity of a sequential extraction process to determine heavy metal binding mechanisms in soils and soil treated with nano-calcium silicate (NCS). A five-step sequential extraction (SE) procedure was adopted on four soils obtained from a sanitary dumpsite, automobile and battery work units from different localities of Bangalore and a steel plant commissioned at Toranagallu, Bellary, India. The soils were mixed with NCS at varying range of 0.5 to 2% by dry weight of the soil. The NCS-amended soils were spiked with cadmium (Cd2+), nickel (Ni2+) and lead (Pb2+) in concentrations to the tune of 3000 mg/kg. It has been observed that there seems to be a gradual increase in binding ability for the targeted heavy metals when soils were amended with NCS compared to untreated soils. This binding phenomenon was attributed to the presence of exchangeable ions, carbonates, oxides of iron and manganese, organic matter and residual fractions. It was noticed that the residual fractions in soils amended with NCS attenuated maximum quantity of metal ions with Pb2+ at 21.46%, followed by 18.8% for Cd2+ and 9.25% for Ni2+ compared to untreated case. Further, this work highlights the role of residual fraction in enhancing the retention capacity of soils by encapsulation of higher concentrations of contaminants. The current study corroborated the fact that the addition of NCS aids in the better encapsulation of selected heavy metal ions.

Quality construction control requires ensuring that compacted fills are properly placed without any significant delay between mixing and compaction of the wet soil mixture. When chemical treatment ...

Sustainable engineering discourages the use of conventional soil stabilizers such as lime and cement owing to their higher carbon emission rates. To address these challenges, many researche...

Soil is a composite material of great interest to civil engineers. When the quality of such composite soils is poor, ground improvement techniques must be adopted to withstand the design load of superstructure. Existing soil stabilizers include lime and cement; however, their environmental safety and sustainable use during stabilization have been receiving increasing attention in recent years. This study investigated the use of granite sand (GS) and calcium lignosulphonate (CLS) as sustainable stabilizers that could be blended with clayey soils. The considered dosages of GS were 30%, 40% and 50%, and those of the CLS were 0.25%, 0.5%, 1% and 1.5%. Direct shear and consolidation tests were performed on the GS–CLS blended soil samples that were cured for 7 and 14 days. The amended stabilizers improved the shear parameters and consolidation characteristics at an optimum dosage of 30% GS and 0.5% CLS. Maximum improvements of 84% and 163% were observed in the cohesion and angles of internal friction, respectively. A significant change was also observed in the consolidation characteristics, making them practically applicable. The soil hydraulic conductivity was reduced by 14%, and the coefficient of consolidation increased by 203% for 30% GS and 05% CLS. Carbon footprint analyses were performed on the soil composition that would be best-suited for a typical homogenous earthen dam section. The results showed that the use of GS and CLS together reduced the carbon emissions by 6.57 and 7.7 times, compared to traditional stabilizers, such as cement and lime.

Natural sands usually consist of considerable fines content (FC) (various proportions of silt and/or clay), the presence of which significantly affects its structure and unsaturated behavior. Soil water characteristic curve (SWCC) is the primary and fundamental tool to address unsaturated soil properties as it relates to the soil suction and the soil water content. However, it is well accepted that the SWCC exhibits hysteresis as it does not follow the same path during desorption and sorption. For a constant value of suction, the soil water content in the desorption is always greater than in the sorption. SWCC considerably changes with the presence of fines in the soil. Therefore, the present study sheds some light on the unsaturated behavior of soil mixtures with varying FC. Ennore sand was reconstituted with various percentages of red soil fines to attain the desired proportions of the soil mixture. The degree of hysteresis between desorption and sorption is presented. The results revealed that increasing the FC in the soil significantly affects the degree of hysteresis. Furthermore, the effect of percentage fines and hysteretic SWCC on the unsaturated infinite slopes has been carried out. It is observed that there is a considerable difference in the factor of safety obtained for the various percentage of fines during sorption and desorption cycles. The present study emphasizes the significance of the influence of FC on the degree of hysteresis of SWCC as it affects slope stability significantly.

Polymers have attracted widespread interest as soil stabilizers and are proposed as an ecologically acceptable means for enhancing the geotechnical properties of soils. They have found profound applications in diverse fields such as the food industry, textile, medicine, agriculture, construction, and many more. Various polymers are proven to increase soil shear strength, improve volume stability, promote water retention, and prevent erosion, at extremely low concentrations within soils through the formation of a polymer membrane around the soil particles upon hydration. The purpose of this work is to provide an overview of existing research on synthetic polymers for soil improvement. A fundamental evaluation of many synthetic polymers used in soil stabilization is provided, Furthermore, the impact of different polymer types on the geotechnical parameters of treated soil was assessed and compared. Limiting factors like polymer durability and the effect of changing climatic conditions on the engineering behavior of the polymer-treated soils have been critically reviewed. The dominant mechanisms responsible for the alteration in the behavior of polymer-soil admixture are reviewed and discussed. This review article will allow practicing engineers to better understand the intrinsic and extrinsic parameters of targeted polymers before employing them in real-field scenarios for better long-term performance

In the design protocols of pavement subgrade layers, the resilient modulus (MR) property assumes importance in evaluating the performance during their life-time under sustainable repeated or dynamics traffic-loads. The aim of this study is to evaluate the improvements achieved on the subgrade layers of fiber-treated lime-blended expansive soil. Two types of fibers exhibiting different surface properties were considered and their length(s) and dosage(s) (by dry weight of soil) were varied as 6 mm and 12 mm; and 0.2% and 0.6%, respectively. To ensure bonding between fiber and soil particles, dehydrated lime has been added to the soil-fiber mixture. The compacted specimens were cured up to 28 days. Dynamic resilient modulus MR tests were carried out in the laboratory for soil–lime-fiber mixtures using dynamic triaxial device. The obtained MR values were correlated with California Bearing Ratio (CBR) and Unconfined Compression Strength (UCS) values and appropriate models have been proposed to estimate MR. The results show significant increments in MR due to fiber reinforcement and are affected by fiber type, length and dosage. The proposed models considering CBR and UCS to predict MR have shown excellent correlations.

Coal gangue is a mine waste generated during the mineral processing phase of coal production. With the surge in demand for coal in thermal power, steel and cement generation industries, the rate of coal gangue generation has reached unprecedented heights. With the realisation of potential threat posed by coal gangue, researchers have made attempts to explore many new avenues of applications for its bulk utilisation. Unfortunately, the implications of coal gangue utilisation on the surrounding environment have not been taken into consideration. In the present study, an attempt has been made to perform carbon footprint analysis on coal gangue to assess the CO2 emissions in utilising it as an embankment material. A similar analysis is done to evaluate the emissions in its disposal process. The results obtained from both the analysis have been compared to assess the feasibility of utilising coal gangue in targeted geotechnical engineering applications. The studies corroborate the fact that the utilisation of coal gangue can lead to a significant decrease in the carbon footprints generation, thus leaving a positive impact on the environment.

This article evaluates the desorption of heavy metals from lime-stabilized, contaminated semi-arid soils under harsh environmental conditions involving chemical extractants, specifically, acetic acid (CH3COOH), nitric acid (HNO3), ethylene diamine tetra-acetic acid (EDTA), and diethylene triamine penta-acetic acid (DTPA). In this study, heavy metals, such as arsenic (As), chromium (Cr), mercury (Hg), and lead (Pb), were spiked with two semi-arid soils (exhibiting different plasticity characteristics) at different load ratios (10–250 mg/kg); they were later stabilized with lime to evaluate the reduction in their mobility. Extensive desorption tests were performed on these soil mixtures to study the efficacy of lime for the in situ fixation of heavy metals. This study revealed that irrespective of the nature and size of the heavy metal, the removal efficiency for the soils was greater than 80%, and EDTA at a concentration of 1 M yielded the maximum removal efficiency. It was found that the cationic metal ions Hg and Pb were desorbed effectively by EDTA, while As was desorbed by HNO3 and Cr by DTPA. The order of desorption for heavy metals was found to be as follows: As > Cr > Hg > Pb. The lime amended soils exhibited lower removal efficiencies (more than 48% retained) due to efficient retention of metals in the soil interstices, making them inert and immobile. There was an improvement of 40% in soils amended with lime compared with virgin soils in the case where soil washing by harsh washing agents was resisted; this proves that the contaminants were embedded in the interstices of the soil calcium interfaces. Therefore, this study asserts the notion that the mobility of heavy metal ions from brownfields can be effectively reduced by in situ lime treatment.

Traditionally, cement and lime are considered as effective stabilizers to improve the geotechnical properties of expansive soils. However, from a sustainable perspective, they discouraged owing to their higher carbon footprint value. To address these negative impacts on the environment, biopolymers are proposed as stabilizers to enhance the geotechnical properties of expansive soil. The present study aims at improving the compressibility characteristics of locally sourced expansive soil using Guar Gum (GG). One-dimensional consolidation tests were performed on GG-treated soil at gum dosages at 0.5, 1.0, 1.5, 2.0 and 2.5% by dry weight of soil mass. The experimental results indicate that the compressibility index of soil with 2.5% GG increased by 1.36 times the compressibility index of untreated soil. This is attributed to the increase in repulsion between negatively charged soil particles and the hydroxyl group (OH−) of GG at a higher dosage.

The hydraulic properties of expansive soils are affected due to the formation of visible cracks in the dry state. Chemical stabilization coupled with fiber reinforcement is often considered an effective strategy to improve the geotechnical performance of such soils. In this study, hydraulic conductivity tests have been conducted on expansive clay using two different types of fibers (fiber cast (FC) and fiber mesh (FM)) exhibiting different surface morphological properties. The fiber parameters include their dosage (added at 0.2% to 0.6% by dry weight of soil) and length (6 and 12 mm). Commercially available lime is added to ensure proper bonding between clay particles and fiber materials, and its dosage was fixed at 6% (by dry weight of the soil). Saturated hydraulic conductivity tests were conducted relying on a flexible wall permeameter on lime-treated fiber-blended soil specimens cured for 7 and 28 days. The confining pressures were varied from 50 to 400 kPa, and the saturated hydraulic conductivity values (ksat) were determined. For FC fibers, an increase in fiber dosage caused ksat values to increase by 9.5% and 94.3% for the 6 and 12 mm lengths, respectively, at all confining pressures and curing periods. For FM fibers, ksat values for samples mixed with 6 mm fiber increased by 12 and 99.2% for 6 and 12 mm lengths, respectively for all confining pressures at the end of the 28-day curing period. The results obtained from a flexible wall permeameter (FWP) were compared with those of a rigid wall permeameter (RWP) available in the literature, and the fundamental mechanism responsible for such variations is explained.

Expansive soils exhibit substantial swelling and shrinkage with the fluctuation in seasonal moisture content. Due to their widespread presence across the world, addressing the problems associated with their volume change has garnered global attention. Traditionally, chemical stabilization using additives like lime and cement was extensively adopted in addressing the swelling phenomenon of expansive soils. In recent times, the use of non-Traditional additives like ground-granulated blast-furnace slag (GGBS) in addressing the swelling and shrinkage of expansive has extensively been promoted as an economical alternative to existing calcium-based additives. Currently, the choice of stabilization technique is primarily driven by design and economic efficiency. However, efforts to quantify environmental impacts prior to the selection of stabilization are scarce. In the present study, carbon footprint analysis (CFA) was performed for lime stabilization, and it was compared with GGBS as an alternative stabilizer in borehole and ponding methods of in situ stabilization. Further, the CFA was also performed for an up-scaled scenario of stabilizing 1-million m2area. From the results, it was observed that the increase in the area of stabilization in the up-scaled scenario has resulted in exponentially rising in the overall emissions 7 × 105times. Further, it was observed that in in situ stabilization of expansive soils, emissions related to embodied carbon are relatively much higher than the haulage/procurement related emissions. From the results, it was inferred that irrespective of the type of additive and scale (volume/area) of stabilization, the application of borehole drilling method with GGBS as an additive could be a prudent practice with substantially lower CO2emissions compared to the ponding method.

The development of alternatives to soil stabilization through mechanical and chemical stabilization has paved the way for the development of biostabilization methods. Since its development, researchers have used different bacteria species for soil treatment. Soil treatment through bioremediation techniques has been used to understand its effect on strength parameters and contaminant remediation. Using a living organism for binding the soil grains to make the soil mass dense and durable is the basic idea of soil biotreatment. Bacteria and enzymes are commonly utilized in biostabilization, which is a common method to encourage ureolysis, leading to calcite precipitation in the soil mass. Microbial-induced calcite precipitation (MICP) and enzyme-induced calcite precipitation (EICP) techniques are emerging trends in soil stabilization. Unlike conventional methods, these techniques are environmentally friendly and sustainable. This review determines the challenges, applicability, advantages, and disadvantages of MICP and EICP in soil treatment and their role in the improvement of the geotechnical and geoenvironmental properties of soil. It further elaborates on their probable mechanism in improving the soil properties in the natural and lab environments. Moreover, it looks into the effectiveness of biostabilization as a remediation of soil contamination. This review intends to present a hands-on adoptable treatment method for in situ implementation depending on specific site conditions.

Soil amelioration is a challenging task in bulk civil engineering applications such as embankment slopes, landfill liner, pavement subgrade, retaining wall back fill. The conventional chemical stabilization techniques (i.e., cement, calcium hydroxide, sodium chloride, calcium chloride, etc.) inherently suffer from associated carbon emissions during their production stages. With the advent of biopolymers derived from natural sources having low embodied energy levels, they can replace conventional stabilizers. The current review article highlights the significant properties of two such biopolymers, i.e., xanthan gum (XG) and guar gum (GG), and their innate potential in stabilizing different soil types including mine tailings. The issues arising with wet and dry mixing of these biopolymers and suggested measures have been critically addressed. The degradation characteristics of biopolymers, which limit their use for bulk civil engineering applications, have been critically discussed, and the potential solutions to overcome durability issues are suggested. Future applications of these biopolymers in geoenvironmental engineering relying on the metal encapsulation properties are discussed in detail. It is believed that the selected biopolymers in this review are renewable, sustainable and remarkable materials with low embodied energy levels and low carbon footprint values compared to existing conventional stabilizers.

Coal gangue is one of the largest industrial residues generated during the coal mining process. The surge in demand for coal has led to further increase in coal gangue production, and its safe disposal is an arduous effort in terms of costs involved and the associated environmental impacts. To address these issues, innovative methods are explored for coal gangue utilization in different fields. The bulk and effective utilization of coal gangue can be attained by using it for various geotechnical applications. Unconfined compressive strength (UCS) of any material plays a major role in its utilization for various geotechnical applications like reclamation fill, fill behind retaining wall, base and sub-base layer. In the present study, the UCS of coal gangue and its variation on addition of lime at different curing periods has been studied. The effect of lime content and curing period clearly manifested with a significant increase in UCS of stabilized coal gangue. The improvement in strength is attributed to the formation of pozzolanic compounds with the curing period.

The current study focuses on studying the effect of almond shell ash (ASA) inclusion along with lime in addressing issues related to strength and volume change behavior of a typical problematic soil. Experiments were carried out on both natural as well as amended soil mixtures having varying percentages of lime and ASA (added based on dry weight of soil). The addition of ASA reduced the plasticity characteristics of selected kaolinite rich clay. Of all the mixtures, the mixture containing 1% ASA and 0.5% lime exhibited maximum optimum moisture content (OMC) and lowest value of maximum dry density (MDD). Upon curing to 28 days, the same mixture exhibited the unconfined compression strength (UCS) value 76 kN/m2. The results pertaining to UCS values indicated that the rate of gain of strength increased proportionally up to 1% ASA addition, followed by which there was a consistent decrease in the rate of gain of strength even in the presence of lime and is attributed to pore saturation with ASA. The addition of lime aids in better binding between non-plastic ASA particles and kaolinite-rich clay which was confirmed by scanning electron microscopic (SEM) images and X-ray diffraction (XRD) studies. SEM images confirmed the presence of agglomerated particles with homogenous mass exhibiting reduced pore opening size for mixture containing both ASA and lime.