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The current study evaluated the potential of crustacean polysaccharide and protein-based biopolymers, namely, chitosan and casein, in ameliorating a low organic soil. The inclusion of these biopolymers will ensure the reusability and recyclability of waste materials derived from the marine industry and dairy industry, respectively. The unconfined compressive strength and consolidated undrained shear parameters were investigated at varying dosages of chitosan and casein (0.5%, 1%, 2%, and 4%) and curing periods (up to 90 days). The compressive strength increased with an increase in the curing period and dosage and led to maximum values of 4.39 and 3.13 MPa for chitosan- and casein-treated soils, respectively, for 4% dosage and 90 days of curing. The effective cohesion (c′) and friction angle (ϕ′) improved after including chitosan and casein. The scanning electron microscopy images revealed that the filler characteristics of chitosan led to strength improvement up to 60 days and developed bond strength via fiber bridging after 60 days of curing at higher dosages. In contrast, the casein–soil mix revealed a higher fibrous structure after a curing period of 28 days, which resulted in strength improvement. This contributed to the highest effective friction angle of 21.57° for the 2% and 60-day-cured casein–soil mix. Casein outperformed chitosan in imparting higher effective shear parameters at 1% and 2% dosages. Fourier transform infrared analysis validated the absence of any new compounds within the soil structure. The research findings on chitosan and casein from the current study recommend the application of these materials for addressing the issues of unstable slopes and pavement subgrade. Practical Applications: The ground improvement industry must shift from environmentally harmful materials to sustainable and nontoxic materials to reduce carbon footprint. Biopolymers are innovative materials derived from various bacteria, plants, and other animals and can impart the required properties for the soils tested (Fatehi et al. 2021). Chitosan and casein are two biopolymers that satisfy the sustainability requirement by being environmentally safe products of waste materials (Chang et al. 2018; Kannan and Sujatha 2023). Applying casein and chitosan has imparted significant improvement in strength to the studied soil. The compressive strength achieved for the fine-grained soils treated with chitosan and casein lies in the range of 0.75–4.39 MPa. Thus, the strength obtained for the treated soils affirms the suitability of these biopolymers in pavement subgrade. The significant improvement in the effective cohesion (c′: 72–179 kPa) and friction angle (ϕ′: 10.57°–21.57°) of amended soils renders the chitosan- and casein-amended samples as excellent shallow foundation materials. Additionally, based on the higher undrained shear strength (125–400 kPa) obtained from consolidated undrained tests, the biopolymers can be recommended for unstable slopes. [ABSTRACT FROM AUTHOR]

In this work, intelligent numerical models for the prediction of debris flow susceptibility using slope stability failure factor of safety (FOS) machine learning predictions have been developed. These machine learning techniques were trained using novel metaheuristic methods. The application of these training mechanisms was necessitated by the need to enhance the robustness and performance of the three main machine learning methods. It was necessary to develop intelligent models for the prediction of the FOS of debris flow down a slope with measured geometry due to the sophisticated equipment required for regular field studies on slopes prone to debris flow and the associated high project budgets and contingencies. With the development of smart models, the design and monitoring of the behavior of the slopes can be achieved at a reduced cost and time. Furthermore, multiple performance evaluation indices were utilized to ensure the model's accuracy was maintained. The adaptive neuro-fuzzy inference system, combined with the particle swarm optimization algorithm, outperformed other techniques. It achieved an FOS of debris flow down a slope performance of over 85%, consistently surpassing other methods. [ABSTRACT FROM AUTHOR]

It has been imperative to study and stabilize cohesive soils for use in the construction of pavement subgrade and compacted landfill liners considering their unconfined compressive strength (UCS). As long as natural cohesive soil falls below 200 kN/m2 in strength, there is a structural necessity to improve its mechanical property to be suitable for the intended structural purposes. Subgrades and landfills are important environmental geotechnics structures needing the attention of engineering services due to their role in protecting the environment from associated hazards. In this research project, a comparative study and suitability assessment of the best analysis has been conducted on the behavior of the unconfined compressive strength (UCS) of cohesive soil reconstituted with cement and lime and mechanically stabilized at optimal compaction using multiple ensemble-based machine learning classification and symbolic regression techniques. The ensemble-based ML classification techniques are the gradient boosting (GB), CN2, naïve bayes (NB), support vector machine (SVM), stochastic gradient descent (SGD), k-nearest neighbor (K-NN), decision tree (Tree) and random forest (RF) and the artificial neural network (ANN) and response surface methodology (RSM) to estimate the (UCS, MPa) of cohesive soil stabilized with cement and lime. The considered inputs were cement (C), lime (Li), liquid limit (LL), plasticity index (PI), optimum moisture content (OMC), and maximum dry density (MDD). A total of 190 mix entries were collected from experimental exercises and partitioned into 74–26% train-test dataset. At the end of the model exercises, it was found that both GB and K-NN models showed the same excellent accuracy of 95%, while CN2, SVM, and Tree models shared the same level of accuracy of about 90%. RF and SGD models showed fair accuracy level of about 65–80% and finally (NB) badly producing an unacceptable low accuracy of 13%. The ANN and the RSM also showed closely matched accuracy to the SVM and the Tree. Both of correlation matrix and sensitivity analysis indicated that UCS is greatly affected by MDD, then the consistency limits and cement content, and lime content comes in the third place while the impact of (OMC) is almost neglected. This outcome can be applied in the field to obtain optimal compacted for a lime reconstituted soil considering the almost negligible impact of compactive moisture. [ABSTRACT FROM AUTHOR]

The current study investigated the efficacy of a protein-based biopolymer called casein for the modification of the primary and secondary compressibility characteristics and ability to resist sustained moisture attack in organic soils. The dry mixing method was adopted for the tests with dosages of 0.5%, 1%, 2%, and 4% added as a percentage of the dry weight of the soil. Incremental consolidation tests indicated that the compressibility reduced with the inclusion of casein, leading to lower void ratios with an increase in consolidation pressure and casein concentration. The primary compression index (Cc) and secondary compression index (Cα) were reduced by 85% and 67%, respectively, for a 2% casein-soil mix at a consolidation pressure of 100 kPa. The compression ratio (Cα/Cc) for the 2% treated soil fell outside the range of 0.01, similar to organic soils with fibrous materials. The permeability was reduced with an increase in casein concentration up to 2% (10−10 m/s) but exhibited a rise at 4% due to the formation of effective flow paths by the formation of inter-aggregate voids. At extended curing periods, the fiber formations contributed to the strength gain in amended soils. However, the successive wetting and drying (w-d) cycles led to fiber detachment and reduced the resistance to moisture attack leading to collapse. The 2%-amended casein-soil mix proved to be most suitable in terms of reduced compressibility and sustained the highest number of w-d cycles. The findings from the current study support the inclusion of casein for short-term applications. The use of this novel material in the ground improvement industry will aid in waste management and recycling, and it can act as a replacement for unsustainable chemical stabilizers such as cement and lime. [ABSTRACT FROM AUTHOR]

The traditional soil stabilization techniques, which primarily include calcium-rich additives, are gradually replaced by environmentally friendly techniques as the former increases the carbon footprint emissions. On the other hand, nanomaterials (particles with a size range of less than 100 nm) are gaining acceptance in geotechnical and geoenvironmental engineering due to their non-toxic nature and less energy consumption required for production. These materials have entirely different properties from conventional materials. When mixed with soil particles, their relatively larger specific surface area values trigger an easy and rapid reaction. The paper reviews the applicability of select nanomaterials such as metallic nanoparticles (which include nano-copper oxide (nano-CuO), nano-magnesium oxide (nano-MgO), iron oxide nanoparticles (nano-Fe2O3), nano-alumina (nano-Al2O3), nano-clay, nano-silica (nano-SiO2), colloidal silica, to name a few, in the areas of geotechnical and geoenvironmental engineering by highlighting the associated mechanisms of interaction. The targeted geotechnical properties include plasticity, compressibility, consolidation, permeability, and strength characteristics under different conditions. Further, the effect of the select nanoparticles on microbial activity, their applicability in remediation of organic and inorganic contaminants from different soil–water systems, and their cost-effectiveness are discussed. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The advent of biopolymers in the ground improvement industry has made significant contributions by reducing the carbon footprint and tremendous improvement in soil engineering properties at par with chemical stabilizers. The current study investigates the effect of two biopolymers, chitosan, and casein on the unconfined compressive strength (UCS) behavior of high-plasticity clay at varying dosages of 0.5%, 1%, 2%, and 4%. The study also evaluates the effect of curing periods up to 90 days on the untreated and biopolymer-treated clay. Chitosan and casein bring a 1428% increase and a 989% increase in UCS at the highest dosage of 4% and the highest curing period of 90 days. The nonlinear multivariate regression models establish a link between the experimental and best-fit data with the coefficient of multiple determination (R2) > 0.98. Additionally, the reliability analysis assesses the efficacy of biopolymer-treated soils as an alternate embankment material. With an increase in curing period of up to 28 days, the chitosan-treated samples exhibit higher factors of safety compared to casein-treated samples. The modified embankment attains a target reliability index of more than 3.0 with minimum Chitosan content (Dch) of 2.25% and Casein content (Dca) of 1.85% at Coefficient of Variation (COV\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$${\text{COV}}$$\end{document}) of UCSmin\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$${\text{UCS}}_{\min }$$\end{document} = 10% for 28-day cured samples. Thus, the reliability analysis presents a rational approach for using biopolymer-treated soils in embankment construction by considering the effect of dosage, curing period, and the variability associated with the UCS. [ABSTRACT FROM AUTHOR]

This study evaluates the unconfined compressive strength (UCS) behavior of biopolymer-modified cohesive soil exposed to natural field conditions. Two biopolymers, xanthan gum (G1) and guar gum (G2), at dosages of 0.5, 1, 2, and 4%, are considered for the study. The performance of biopolymers under natural curing simulates the field conditions better. To assess the stability of biopolymer-modified soil, UCS specimens were subjected to daily variations in temperature and relative humidity, for curing periods of 7, 14, 28, 45, and 60 days. UCS test results indicate that the dehydration caused due to natural curing resulted in a significant increase in UCS, owing to the crosslinking of individual soil particles with hardened biopolymer for both G1 and G2. The effects of dosages of G1 and G2, as well as curing period, on UCS are represented by multivariate regression equations based on experimental data collected after the employed curing periods. The influence of the curing period on UCS of untreated cohesive soils is also provided using nonlinear regression equations. The dosages of G1 and G2 required to stabilize the cohesive soils for curing periods of 7 and 28 days for the construction of embankments are computed using deterministic design and target reliability-based design optimization (TRBDO). The results obtained using these approaches reveal that the factor of safety and reliability index against UCS failure of embankment increases significantly with the increase in G1 content from 0.5% to 4%. On the contrary, when the cohesive soils are blended with G2 with a dosage of 0.5% to 2.9%, the factor of safety and reliability index continued to increase significantly. However, the addition of G2 beyond 2.9% reduces the factor of safety and reliability index considerably. The results indicate that the optimum dosage of G2 is 2.9%. The TRBDO provides a reasonable and systematic procedure for the optimum design of embankments for biopolymer-blended cohesive soils. [ABSTRACT FROM AUTHOR]

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 researchers considered biopolymer stabilization, a promising green technique in geotechnical engineering practice for treating expansive soils. This study evaluated the performance of two biopolymers, xanthan gum (XG) and guar gum (GG), in improving the unconfined compressive strength (UCS) and consolidation characteristics of an expansive soil subjected to different testing conditions. The dosage of the biopolymers (XG and GG) was maintained at 0.5%, 1%, 2%, and 4% by weight of dry mass of soil mass. Biopolymer treated samples were subjected to desiccator and natural curing conditions (i.e., specimens were exposed to different temperature and relative humidity conditions) for 7, 14, 28, 45, and 60 days. Results showed that the UCS of biopolymer-treated soil increased with increased dosage up to 2% and 1% for XG and GG, respectively; strength significantly improved during the first 28 days of curing under controlled conditions. Improvement of strength was due to increased adhesive strength between gum strands and soil particles. One-dimensional fixed-ring oedometer consolidation test results indicated that the compressibility and swelling characteristics of biopolymer-treated soil increased due to the hydrophilic nature of gum and an increase in the repulsive forces between negatively charged clay particles and the respective functional groups of XG and GG. Scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR) were performed on both untreated and biopolymer-treated soil to evaluate the interaction mechanism between soil and biopolymer strands. The microlevel studies confirmed the crosslinking of soil particles by gum strands, which aids in the strength improvement. [ABSTRACT FROM AUTHOR]

In this article, the effect of randomly oriented polypropylene fiber inclusion in enhancing the various geotechnical properties (unconfined compression strength, compressibility index, swell index, hydraulic conductivity, linear shrinkage, California bearing ratio) of a typical expansive semiarid soil is studied. Since the practicing engineer typically has difficulty in selecting the right mix of fiber type, dosage, and lime content to meet the optimum requirements of this targeted group of geotechnical properties, PROMETHEE is here adopted in order to assist in the decision-making process. The primary objective of this study was to evaluate different geotechnical properties for possible alternatives, the first being untreated soil itself and the second treating the soil with 6% lime. The remaining alternatives vary with fiber type, fiber size, and fiber dosage with or without lime. A further objective was to study the combined influence of factors, viz. lime addition, fiber type, fiber dosage, and fiber length at their respective levels of interactions for the targeted soil properties. The results of the study led to the identification of groups of criteria expressing similar preferences. Sensitivity analysis was carried out in order to better understand the conflicts to be solved in order to make this decision. [ABSTRACT FROM AUTHOR]

Thermal power stations in most countries are burdened with the problem of fly ash disposal, and unless suitable uses are found for fly ash, it will pose a gigantic problem for the power sector. The disposal of huge quantities of fly ash without proper care significantly impacts the environment, particularly by creating soil and groundwater contamination. However, it is essential to note that fly ashes have many desirable properties that can find application in civil engineering in general and in geotechnical engineering in particular. This article reviews the literature dealing with the generation of fly ashes and briefly describes their desirable properties with respect to geotechnical and geoenvironmental applications. Desirable properties include pozzolanic reactivity along with mineralogical and morphological physiognomies that enhance surface adsorption of toxic heavy-metal ions. These properties are delineated further in this review article. The stabilizer effect on the geotechnical behavior of fly ashes is addressed with emphasis on morphological and mineralogical aspects. One of the limiting factors of stabilization, lime leachability and its effect on durability and long-term performance, is discussed. Various environmental concerns associated with the use of fly ashes are also addressed. [ABSTRACT FROM AUTHOR]

Ferroelectric materials are used in a number of applications such as sensors, transducers, actuators, health monitoring and micro-electromechanical systems. The ability of these materials to combine electrical and mechanical responses has led to the establishment of many energy harvesting and conversion systems. Energy harvesting from mechanical vibrations using ferroelectric (subclass of piezoelectric) materials has been extensively studied over the last several decades. However, most of these possess low energy conversion density. Many researchers are working in the direction of improving energy conversion density in these materials. In this study, an attempt has been made to shed some light on the mechanical energy harvesting potential of ferroelectric Pb(Mn1/3Nb2/3)O3-32PbTiO3(PMN-PT) single crystal through the use of Olsen-like (Ericson) cycle. A maximum energy conversion density of 160 kJ/m3is obtained for operation parameters of 0–1.5 MV/m and 2–28 MPa stress interval at 80°C. The reported energy density is higher than that of most of other energy harvesting techniques using PMN-PT. The results motivate possible use of this technique for mechanical energy harvesting in ferroelectric materials. [ABSTRACT FROM AUTHOR]

Ferroelectric materials are used in many applications including, high-voltage generator, sonar, medical, electro-acoustic coupling, filters circuits and many more. In this work, the compositional dependence and stress dependence of the electromechanical properties of [011]Crelaxor ferroelectric (1-x-y)Pb(In1/2Nb1/2)O3–xPb(Mg1/3Nb2/3)O3–yPbTiO3(PIN-PMN-PT) single crystals has been determined. The specimens were subjected to mechanical loading and mechanical energy converted was found out by using Olsen-like cycle. It can be inferred that as the applied stress increases, converted energy density also increases. The maximum energy converted was found out to be 98.8 kJ/m3for composition 0.32PIN-0.38PMN-0.30PT between 0 to 36 MPa. Also, the energy storage density for the specimens was found out. The maximum energy stored was found to be 98.8kJ/m3for 0.24PIN-0.46PMN-0.30PT. [ABSTRACT FROM PUBLISHER]

In order to explore the possibility of using low-lime fly ashes, the physical and chemical properties which have a direct bearing on their geotechnical and geoenvironmental behaviors have been investigated. In this paper, two types of low-lime fly ashes, originating from India, have been used. Abrief account of various methods adopted in characterizing their physical, chemical, and geotechnical properties is presented. The relative importance of each of these properties in enhancing the bulk applicability of fly ashes has been brought out. [ABSTRACT FROM AUTHOR]

The technical feasibility of utilization of fly ash as a low-cost adsorbent for the removal of metals from water has been studied. For two types of fly ashes, the retention capacities of copper, lead, and zinc metal ions have been studied. Contact time, initial concentration, and pH have been varied and their effect on retention mechanism has been studied. The dominant mechanisms responsible for retention are found to be precipitation due to the presence of calcium hydroxide, and adsorption due to the presence of silica and alumina oxide surfaces in the fly ash. First-order kinetic plots have revealed that the rate constant increases with increase in the initial concentration and pH. Langmuir adsorption isotherms have been plotted to study the maximum adsorption capacities for metal ions considered under different conditions. X-ray diffraction studies revealed the formation of new peaks corresponding to respective metal ions precipitates under alkaline conditions. [ABSTRACT FROM PUBLISHER]

The strength of fly ash mixture often needs to be enhanced for its better utilization in geotechnical and environmental applications. Many fly ashes often improve their strength with lime but may not meet the requirements. Gypsum, which reduces the lime leachability, further improves the strength. An attempt is made in this paper to study the effect of gypsum on the strength development of two Class F fly ashes with different lime contents after curing them for different periods. The sustainability of improved strength has been examined after soaking the cured specimens in water and with different leachates containing heavy-metal ions. The strength of both the fly ashes investigated improved markedly up to a particular amount of the lime content, which can be taken as optimum lime content, and thereafter the improvement is gradual. The improvement in strength at higher lime contents continues for a longer period (even up to 180 days). Gypsum accelerates the gain in strength for lime-stabilized fly ashes, particularly in the initial curing periods at about optimum lime content. At high lime contents gypsum attributes very high strength after curing for long periods mainly due to the alteration of fly ash lime reaction compounds. Gypsum not only improves the reduction in the loss of strength due to soaking even at low curing periods but also improves the durability of stabilized fly ashes due to repeated cycles of wetting and drying. [ABSTRACT FROM AUTHOR]

Modern innovations increasingly prioritize eco-friendliness, aiming to pave the way for a sustainable future. The field of civil engineering is no exception to this approach, and, in fact, it is associated with almost every sustainable development goal framed by the United Nations. Therefore, the sector has a pivotal role in achieving these goals. One such innovation is exploring the possibilities of using nature-friendly materials in different applications. Biopolymers are substances that are produced either by the chemical synthesis of natural materials or by the biosynthesizing activities of microorganisms. Microbial-derived biopolymers are known for their non-toxic and nature-friendly characteristics. However, their applications are mostly restricted to the field of biotechnology and not fully explored in civil engineering. This article reviews various microbial-derived biopolymers, focusing on the types available on the market, their source and properties, and more importantly, their wide range of applications in the civil engineering field. Additionally, the article explores the prospects for future research and the potential for the practical implementation of these techniques in the pursuit of a sustainable future. [ABSTRACT FROM AUTHOR]

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 [ABSTRACT FROM AUTHOR]

Acacia gum (AG), a polysaccharide biopolymer, has been adopted to improve the strength of three cohesive soils by subjecting them to diverse environmental aging conditions. Being a polysaccharide and a potentially sustainable construction material, the AG yielded flexible film-like threads after 48 h upon hydration, and its pH value of 4.9 varied marginally with the aging of the stabilized soils. The soil samples for the geotechnical evaluation were subjected to wet mixing and were tested under their Optimum Moisture Content (OMC), as determined by the light compaction method. The addition of AG modified the consistency indices of the soils due to the presence of hydroxyl groups in AG, which also led to a rise in OMC and reduction in Maximum Dry Unit weight (MDU). The Unconfined Compressive Strength (UCS) and California Bearing Ratio (CBR) were determined under thermal curing at 333 K as well as on the same day of sample preparation. The least performing condition of the soil's CBR was evaluated under submerged conditions after allowing the AG-stabilized specimens to air-cure for a period of 1 week. The UCS specimens tested after 7 days were subjected to the initial 7 days of thermal curing at 333 K. A dosage of 1.5% of AG yielded the UCS of 2530 kN/m2 and CBR of 98.3%, respectively, for the low compressible clay (LCC) after subjecting the sample to 333 K temperature for 1 week. The viscosity of the AG was found to be 214.7 cP at 2% dosage. Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), and average particle size determination revealed the filling of pores by AG gel solution, adsorption, and hydrogen bonding, which led to improvements in macroproperties. [ABSTRACT FROM AUTHOR]

Soil reinforcement using synthetic fibers is a proven technique for enhancing engineering properties to meet the requirements of subgrade materials for pavement projects. The safe and economical design of fiber-reinforced pavement layers requires better insights into their unsaturated behavior. The soil–water characteristic curve (SWCC) is a measure of the water content inside soil pores at a given suction and is considered an essential property to better understand or predict the behavior of unsaturated fiber-reinforced soils. This paper centers on investigating the soil–water characteristic curves for typical expansive clay reinforced with two different types of polypropylene fibers having different surface morphological properties. The effect of an increase in the fiber dosage (0.2% and 0.6% by dry weight of soil) and fiber lengths (6 and 12 mm) on the resultant SWCC patterns is investigated. The addition of lime is considered to enhance the bonding between clay particles and fiber elements to ensure better friction mobilization levels. SWCCs were determined for all experimental mixtures using a combination of axis translation and filter paper techniques that cover the entire matric suction range during measurements. Volume changes undergone during suction measurements have been duly highlighted and discussed. Furthermore, the one-dimensional deformation (swelling/consolidation) characteristics of these lime-blended fiber-reinforced mixtures at different levels of initial matric suction are studied, and the correlations between initial matric suction with both compression index (Cc) and swell index (Cs) are established. The results indicate a significant change in the shape of the SWCC for lime-blended fiber-reinforced mixtures compared with the shape of the SWCC for natural clay. The contribution of fiber inclination to altering the shape of the SWCC curve is observed as slight regardless of the type, length, and dosage of fiber. Compression and swell indices for tested mixtures increased proportionately with an increase in initial matric suction levels. Doubling the length of the fiber also induced an increase in the compression index. Under no stress conditions did both fiber type and fiber length have a marginal effect on the swell potential and SWCCs. [ABSTRACT FROM AUTHOR]

The present infrastructure regime being promoted by the United Nations Sustainable Development Goals is such that by the year 2050, the use of cement in the production of concrete and its use in the general construction activities as to reduce carbon emissions to zero must be replaced with net-zero construction materials. These cement replacement materials should be pozzolanic enough to either partially or totally replace the conventional cement and reduce its carbon footprint. The current study adopts two machine learning techniques: gene expression programming (GEP) and artificial neural network (ANN) to determine the 56 days and 180 days of net-zero compressive strength of fly ash concrete. The study effectively depicts how machine learning techniques can be used for the prediction of long- and short-term compressive strength of fly ash concrete toward a carbon neutrality infrastructure regime. The dataset has been compiled by various researchers, and the input parameters include cement, fine aggregate, coarse aggregate, fly ash, water, and water/binder ratio. And the 56 days and 180 days compressive strength (fck) values are the targeted output values. In order to determine a better model, both GEP and ANN were assessed based on the values of the correlation coefficient and crosschecked by other statistical parameters. Both models performed well; however, GEP outweighs the ANN model in estimating the fck at 56 days and 180 days. Moreover, the GEP model generated a simplified equation for foreseeing the value of fck for different ages of net-zero fly ash concrete. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

One of the significant issues persisting in the study of soil stabilization is the establishment of the optimum proportions of the quantity of stabilizer to be added to the soil. Determining optimum solutions or the most feasible remedies for the utilization of stabilizing products in terms of their dose rates has become a significant concern in major civil engineering design projects. Using the response surface methodology, this study primarily focused on investigating the optimal levels of reinforcement fiber length (FL), fiber dosage (FD), and curing time (CT) for geotechnical parameters of stabilized soil. To realize this objective, an experimental study was undertaken on the California bearing ratio (CBR) and unconfined compressive strength (UCS). Hydraulic conductivity (HC) tests were also performed, with stabilizer proportions of 6–12 mm for the FL and 0.2–0.6% for the FD calculated for the total dry weight of soil and 6% lime (total weight of dry soil). The curing times used for testing were 0, 7, and 14 days for the CBR tests; 60, 210, and 360 days for the UCS tests; and 7, 17, and 28 days for the HC tests. All practical experiments were conducted with experimental techniques using stabilizer proportions and curing times. The FL, FD, CT, CBR, UCS, and HC response factors were determined using the central composite design. The results point toward a statistically significant model constructed (p ≤ 0.05) using the analysis of variance. The results from this optimization procedure show that the optimal values for the FL, FD, and CT were 11.1 mm, 0.5%, and 13.2 days, respectively, as these provided the maximum values for the CBR; 11.7 mm for the FL, 0.3% for the FD, and 160 days for the CT corresponded to the maximum values for the UCS; and 10.5 mm for the FL, 0.5% for the FD, and 15 days for the CT led to the minimum value for the HC. In practice, the suggested values may be useful for experiments, especially for preliminary assessments prior to stabilization. [ABSTRACT FROM AUTHOR]

This article presents the effect of processing parameters on the ferroelectric hysteresis behavior of Ba0.85Sr0.15Zr0.1Ti0.9O3(BSZT) ceramics. The ferroelectric hysteresis scaling relations for coercive field (Ec) and remnant polarization (Pr) as a function of temperature have been proposed. The power law temperature exponents based on scaling were systematically established for all the hysteresis parameters. The temperature dependent scaling of Ecand Prat sintering temperature of 1400, 1425, 1450 and 1475°C yields EcαT0.43, EcαT0.84, EcαT0.50, EcαT0.37and PrαT−1.73, PrαT−1.55, PrαT−1.73, PrαT−1.69respectively. Additionally, the scaling relations for the samples sintered at 1450°C at different time intervals of 3, 4, 5 and 6 hrs were also established. Finally, to understand the domain dynamics, back switching polarization (Pbc) as a function of temperature (T) was also estimated by Arrhenius law and the average activation energy was evaluated. [ABSTRACT FROM PUBLISHER]