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This investigation addresses the reinforcement of rammed earth (RE) structures by integrating carpet polyacrylic yarn waste (CPYW) generated from the carpet production process and employing Ground Granulated Blast-Furnace Slag (GGBS) as a stabilizer, in conjunction with alkali activators potassium hydroxide (KOH), to enhance their mechanical properties. The study included conducting Unconfined Compressive Strength (UCS) tests and Brazilian Tensile Strength (BTS) tests on plain samples, GGBS-stabilized (SS) samples, CPYW-reinforced (CFS) samples, and samples reinforced with a combination of GGBS and CPYW (SCFS). The results showed that the mechanical and resistance properties of the CFS and SCFS samples were improved; these findings were confirmed by the presence of more cohesive GGBS gel and fibers as seen in FE-SEM and microscopic images. Therefore, the use of GGBS and CPYW, both separately and in combination, is suggested as a viable approach to enhance mechanical performance and reduce the brittle failure propensity of RE structures. This study achieved significant improvements in the mechanical behavior of RE structures by integrating CPYW and alkali-activated GGBS. Results showed a 370% improvement in UCS and a 638% increase in BTS than the plain sample. These enhancements demonstrate the potential for using industrial waste in eco-friendly, high-performance construction materials. [ABSTRACT FROM AUTHOR]

Purposes This study is conducted to explore the indirect measurement method of mechanical properties of solidified heavy metal contaminated soil. Methods The combined resistivity-unconfined compression test method was carried out to investigate the strength and electrical properties of solid waste solidified contaminated soil. Findings The results show that the red mud-carbide slag-phosphogypsum solidified contaminated soil has higher strength, in which, both peak stress and failure strain increase with the increase of curing age. The solidified soil also exhibits a stable change law between its strength and resistivity. There is a stable variation law between the strength and resistivity of the solidified soil, which shows a good linear relationship. A power function relationship between strain and dynamic resistivity is also observed through stress-strain-dynamic resistivity curve analysis. An electrical characterization model of mechanics is established by replacing the strain with dynamic resistivity in the strain softening model. Coincidence degree of the model is high according to comparison and verification, indicating that the dynamic resistivity change value has high reliability to represent the stress and deformation performances of the solidified soil.

In the current study, the agricultural waste materials Date Seed Ash (DSA) is investigated. Various concentrations of DSA (5%, 10%, 15%, and 20%) were applied, and the impact of DSA on the surface morphology and chemical composition of the tested soil (soft clay) was examined using scanning electron microscopy and energy dispersive X-ray. The results indicated that soft clay soil treated with DSA exhibited increased overall strength. By adding 15% DSA, the unconfined compression strength improves to more than double that of the sample without any treatment. Moreover, examining the morphology of soil samples treated with 10% and 15% DSA uncovered the formation of hydrated particles and cement-like compounds resulting from the interaction between the soil and DSA. In addition, as the DSA % grows, the compressibility and volume change factors decrease. The California Bearing Ratio and unconfined compression strength tests confirmed that DSA was an effective stabilizer of soft clay soil. In this study, the most effective amount of Date Seeds Ash (DSA) was 15% by adding weight to enhance the fundamental properties, and strength of soft clay soil. [ABSTRACT FROM AUTHOR]

Stabilization/solidification (S/S) is an effective method used to reduce the leaching of heavy metals from soils, which is a serious environmental problem when soil is contaminated with heavy metals. In this study, a new stabilizing agent consisting of acetate-ethylene copolymer emulsion (VAE)-hydrated calcium silicate-polycarboxylate (V-CSH-PCE), water-soluble thiourea-formaldehyde (WTF) resins, cement, and fly ash was prepared for the solidification of heavy metal-contaminated soil under low-temperature conditions. The results showed that the agents significantly enhanced the compressive properties of the soil. When 10% cement, 8% fly ash, 1.5% V-CSH-PCE, and 0.5% WTF were added, the compressive strength of the subsoil after 1 day of curing was 0.3755 MPa, which was nearly 12 times higher compared with a blank sample. Meanwhile, the leaching concentrations of Cu2+, Zn2+, Pb2+, and Cr3+ in the substrate were 2.52, 1.12, 1.32, and 0.51 mg/L, respectively, which were lower than the leaching standard of "Hazardous Waste Identification Standard Leaching Toxicity Identification (GB 5085.3-2007)". In addition, the compressive strength of the soil after 1 day of curing at a low temperature (4 °C) was 0.2915 MPa, which was 30.9% higher compared with the soil without the V-CSH-PCE. The results showed that the cement-fly ash-(V-CSH-PCE)-WTF mixture has good application prospects in improving the compressive strength of soil and stabilizing heavy metal ions. [ABSTRACT FROM AUTHOR]

Tailing storage facilities are very complex structures whose failure generally leads to catastrophic consequences in terms of casualties, serious environmental impacts on local biodiversity, and disruptions in the mineral supply. For this reason, structures at risk must be reinforced or decommissioned. One possible option is its reinforcement with compacted filtered tailings stabilized with binders. Alkali-activated binders provide a more sustainable solution than ordinary Portland cement but require an optimization of the tailing–binder mixture, which, in some cases, can lead to a substantial experimental effort. Statistical models have been used to reduce the number of those experiments, but a rational design methodology is still lacking. This methodology to define the right mixture for a required strength should consider both the mixture components and in situ conditions. In this paper, response surface methods were used to plan and interpret unconfined compression strength test results on an iron tailing stabilized with alkali-activated binders. It was concluded that the fly ash content was the most important parameter, followed by the liquid content and sodium hydroxide concentration. From the obtained results, several statistical models were defined and compared according to the definition of a strength prediction model based on a mixture index parameter. It was interesting to observe that models with the porosity cement index still provide reasonable adjustment even when different tailings' water contents are considered. [ABSTRACT FROM AUTHOR]

This study presents a pioneering approach that combines artificial intelligence and a nature-inspired optimization algorithm to predict soil unconfined compressive strength (UCS). The traditional laboratory-based method of UCS measurement, involving soil sample preparation, is time-consuming, labour-intensive, and prone to low accuracy. In this work, we propose a non-destructive soil UCS measurement technique utilizing robust AI-based models based on ensemble learning and hybrid learning techniques. Support vector machine (SVM) coupled with particle swarm optimization (PSO), extreme gradient boost (XGB), K-nearest neighbour (KNN), and nature-inspired optimization algorithm-based six hybrid ANFIS models, employing input features from experimental data, were adopted for UCS prediction. Model performance was assessed using standard metrics such as root mean square error, mean absolute error, variance account factor (VAF), expanded uncertainty (U95), and coefficient of determination (R2) between predicted and actual unconfined compressive strength. The study employed 274 data points generated in our laboratory. Sensitivity analysis and Pearson correlation techniques were employed to select relevant elements as input features. Fine content, coarse content, liquid limit, plastic limit, plasticity index, and cohesion of soil were identified as the most effective configurations for accurate soil UCS predictions. XGB demonstrated the highest prediction efficiency in the training and testing phase, achieving an impressive R2 of 99.2 and 96.8%, respectively. The results also emphasize the importance of the selected features. The experimental validation accuracy of 97% for the developed XGB model, whose data were not used during model calibration and verification, confirmed the generalization capability of the models. This study provides valuable insights for policymakers and industry stakeholders, facilitating optimized soil unconfined strength management practices. [ABSTRACT FROM AUTHOR]

Covid-19 pandemisi ile birlikte dünya genelinde tek kullanımlık yüz maskesi kullanımı büyük artış göstermiştir. Bu kullanılmış maskelerin artışı çevre için büyük tehdit oluşturmakla birlikte, bertaraf edilmesi de problem olarak ortaya çıkmıştır. Bu problemin çözümü için yüz maskelerinin zemin iyileştirmede kullanımının bir yöntem olacağı düşünülmüştür. Bu nedenle 0,5*3 cm boyutlarındaki yüz maskeleri %0,2-0,4-0,6-0,8-1 oranlarında düşük plastisiteli kil ile karıştırılarak Bender element ve Serbest basınç deneylerine tabi tutulmuştur. Yapılan serbest basınç deney sonuçlarına göre yüz maskesinin belirli bir orana kadar dayanımı arttırdığı, daha sonra ise dayanımı düşürdüğü görülmüştür. Yapılan bender element testlerine göre maske liflerinin yüksek birim hacim ağırlıkta kayma dalgası hızının azalmasına ancak düşük birim hacim ağırlığındaki numunelerde kayma dalgası hızının öncelikle arttığı, daha sonra azaldığı görülmüştür.

Soil in road pavement construction has an important role as the foundation for the structure supporting the load above it. The damage that occurs in road construction also often due to subgrade soil that does not have good bearing capacity, therefore soil reinforcement or stabilization is needed to improve its strength. The road section in Cibingbin Village, Cibaliung subdistrict, Pandeglang Regency was damaged due to a lack of soil bearing capacity, where through field CBR tests it was discovered that the CBR value of the soil was 3% less than required. Soil strengthening can be done by adding additional substances to the soil which can increase its strength and bearing capacity. Eggshell powder was chosen in this research as an additive to see its effect on soil strength. Soil strength is tested through unconfined compression stress (UCS) testing in the laboratory. Apart from that, the effect of adding eggshell powder on the physical properties of the soil was also studied. Variations in adding eggshell powder were taken in varying percentages 0%, 2%, 4%, 6%, 8%, 10%, 12% and 14%. The results of testing the physical properties of the soil showed that the original soil type was classified as organic clay with high plasticity (CH). The UCS test results on the original soil had a strength (qu) value of 1.6 kg/cm2, and the adding eggshell powder could increase the qu value which got optimum value at the percentage 12% eggshell powder with 0 and 3 days of curing of 2.851 kg/cm2 and 3.386 kg/cm2 respectively. It can be concluded that the addition of eggshell powder can increase the soil strength. The consistency of the clay soil changes to become stronger and based on the UCS value the clay soil becomes stiffer.

This study delves into the mechanical properties and mechanisms of bentonite-modified cement soil, a reinforced material formed through the physicochemical reactions of cement, soil, and water. Recognizing the material’s widespread application in foundation treatment, slope reinforcement, and seepage control, alongside the environmental pressures of cement production, this research explores the potential of bentonite as a partial cement substitute. Through indoor unconfined compressive strength and permeability tests, varied by curing age, bentonite type, and mix ratio, the study assesses the impact of these factors on the material’s performance. Microscopic analyses further elucidate the intrinsic mechanisms at play. Key findings include: a non-linear relationship between bentonite content and modified cement soil strength, with sodium-based bentonite enhancing strength more effectively than calcium-based; a significant reduction in permeability coefficient with increased bentonite content, particularly with sodium-based bentonite; and a detailed examination of the material’s microstructure, revealing the critical role of cement and bentonite content in pore reduction and strength enhancement. The study underscores the paramount influence of cement content on both strength and permeability, proposing a prioritized framework for optimizing modified cement soil’s performance.

This paper presents an experimental study of nanomaterials' influence on improving the mechanical behaviour and microstructure of cemented soils. The strength characteristics were obtained through uniaxial compressive strength test. The influences of nanomaterials on the pore size distribution and micromorphology of cemented soil were investigated by nuclear magnetic resonance, scanning electron microscope, and X-ray diffraction. The results show that the uniaxial compressive strength of the cemented soil increases with the nano-SiO2 content. When the content is 4%, the strength of the cemented soil increases by about 40%. Improvement with nano-Fe3O4 shows different trends. The strength of the cemented soil increases with the nano-Fe3O4 content, reaching a peak at 3% of the nano content, and then decreases with the increase in the content. The transverse relaxation time spectrum curve of the cemented soil is trimodal, and the main peak covers a dominant area. Adding nanomaterials improves the pore distribution, transforms large pores into small pores, and greatly reduces the pores of the cemented soil. The porosity of the cemented soil decreases exponentially with the increase of nano-SiO2 content. On the contrary, with the increase of nano-Fe3O4 content, the porosity of the cemented soil specimen first decreases and then increases, the porosity reaches the minimum at 3% content. Nano-SiO2 and nano-Fe3O4 can effectively fill the internal pores of the cemented soil and accelerate the hydration process. In addition, nano-SiO2 participates in the hydration reaction of cement and has a good promoting effect on the mechanical properties of cemented soil. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Ground Improvement is the property of Journal of Ground Improvement Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Railway Science & Engineering is the property of Journal of Railway Science & Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Teknika: Jurnal Sains dan Teknologi is the property of Teknika: Jurnal Sains dan Teknologi, Universitas Sultan Ageng Titayasa and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The cement composite calcium lignosulfonate is used to enhance the mechanical properties and the freeze–thaw resistance of loess. Based on an unconfined compressive test under different freeze–thaw cycles, the influence of cement dosage, curing age, and freeze–thaw cycles on compressive strength are discussed. The results indicate that the strength of loess can increase by up to 13 times, and the loss of strength is reduced from 72% to 28% under the reinforcement of cement dosage and curing age. The loss of strength is mainly concentrated in the initial 5 freeze–thaw cycles, and the structure gradually stabilizes after 10 freeze–thaw cycles. In addition, according to the X-ray diffraction test, it is found that the stabilized loess exhibits a comparatively more stable mineral composition. The scanning electron microscope results reveal that hydration products enveloped the soil particles, forming a mesh structure that strengthens the connection between the soil particles. The freeze–thaw damage makes the small and medium pores turn into large pores in loess, while the stabilized loess changes micro and small pores into small and medium pores, with no large pores found. It is feasible to improve loess with the cement composite calcium lignosulfonate, which can provide references for the reinforcement treatment of loess. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Ground Improvement is the property of Journal of Ground Improvement Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Ground Improvement is the property of Journal of Ground Improvement Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Although cemented soil as a subgrade fill material can meet certain performance requirements, it is susceptible to capillary erosion caused by groundwater. In order to eliminate the hazards caused by capillary water rise and to summarize the relevant laws of water transport properties, graphene oxide (GO) was used to improve cemented soil. This paper conducted capillary water absorption tests, unconfined compressive strength (UCS) tests, softening coefficient tests, and scanning electron microscope (SEM) tests on cemented soil using various contents of GO. The results showed that the capillary water absorption capacity and capillary water absorption rate exhibited a decreasing and then increasing trend with increasing GO content, while the UCS demonstrated an increasing and then decreasing trend. The improvement effect is most obvious when the content is 0.09%. At this content, the capillary absorption and capillary water absorption rate were reduced by 25.8% and 33.9%, respectively, and the UCS at 7d, 14d, and 28d was increased by 70.32%, 57.94%, and 61.97%, respectively. SEM testing results demonstrated that GO reduces the apparent void ratio of cemented soil by stimulating cement hydration and promoting ion exchange, thereby optimizing the microstructure and improving water resistance and mechanical properties. This research serves as a foundation for further investigating water migration and the appropriate treatment of GO-modified cemented soil subgrade. [ABSTRACT FROM AUTHOR]

Copyright of New Building Materials / Xinxing Jianzhu Cailiao is the property of New Building Materials Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Ground Improvement is the property of Journal of Ground Improvement Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The experimental study of geopolymeric stabilized samples based on ceramic waste powder (CWP) and sodium hydroxide solution acting as an alkali activator was investigated in the present research to evaluate the possibility of geopolymeric stabilization of silty sand soil as a sustainable method for improving the mechanical properties of inshore sand soils. X-ray fluorescence spectroscopy (XRF) was employed to analyze and determine the chemical components of the CWP and natural soil. The effect of four factors on the unconfined compression strength (UCS) and failure strain (Ɛf) of silty sand soil, including CWP content (0–24%), NaOH solution concentration (0–15 M), the curing time (7, 28, and 91 days), and the initial curing temperature (25°C and 70°C), were investigated. The results demonstrated a substantial increase in both UCS and Ɛf for geopolymeric stabilized samples in comparison to natural soil and the soil that was stabilized with 5% ordinary Portland cement (OPC). The UCS and Ɛf values of the 28-day-cured optimal sample (CWP = 15% and NaOH solution concentration = 6 M) in comparison with natural soil increased from 0.080 to 2.22 MPa and from 2.31% to 5.45%, respectively. Moreover, the UCS value in this sample was 1.75, 1.81, and 1.29 times higher than the stabilized soil with 5% OPC for each curing time. Without an alkali activator, CWP addition to the soil had no effect on UCS at all curing times. However, when a 2 M NaOH solution was added to the soil without CWP, the UCS of this sample rose to 0.36 MPa after 7 days of curing. The UCS of geopolymeric stabilized samples experienced growth from 1.27 to 2.04 times by shifting the initial curing temperature from 25°C to 70°C. Through the use of energy-dispersive X-ray (EDX) spectra and scanning electron microscope (SEM) photomicrograph, the microstructure of stabilized samples was inspected. SEM photomicrographs corroborated the UCS test findings, and EDX analysis confirmed the high quality of the aluminosilicate gels' growth and production. To sum up, soil stabilization using CWP geopolymer is a cost-effective, environmentally friendly method that reduces the consumption of natural resources and energy.

Tailing storage facilities are very complex structures whose failure generally leads to catastrophic consequences in terms of casualties, serious environmental impacts on local biodiversity, and disruptions in the mineral supply. For this reason, structures at risk must be reinforced or decommissioned. One possible option is its reinforcement with compacted filtered tailings stabilized with binders. Alkali-activated binders provide a more sustainable solution than ordinary Portland cement but require an optimization of the tailing–binder mixture, which, in some cases, can lead to a substantial experimental effort. Statistical models have been used to reduce the number of those experiments, but a rational design methodology is still lacking. This methodology to define the right mixture for a required strength should consider both the mixture components and in situ conditions. In this paper, response surface methods were used to plan and interpret unconfined compression strength test results on an iron tailing stabilized with alkali-activated binders. It was concluded that the fly ash content was the most important parameter, followed by the liquid content and sodium hydroxide concentration. From the obtained results, several statistical models were defined and compared according to the definition of a strength prediction model based on a mixture index parameter. It was interesting to observe that models with the porosity cement index still provide reasonable adjustment even when different tailings’ water contents are considered.

Stabilization/solidification (S/S) is an effective method used to reduce the leaching of heavy metals from soils, which is a serious environmental problem when soil is contaminated with heavy metals. In this study, a new stabilizing agent consisting of acetate-ethylene copolymer emulsion (VAE)-hydrated calcium silicate-polycarboxylate (V-CSH-PCE), water-soluble thiourea-formaldehyde (WTF) resins, cement, and fly ash was prepared for the solidification of heavy metal-contaminated soil under low-temperature conditions. The results showed that the agents significantly enhanced the compressive properties of the soil. When 10% cement, 8% fly ash, 1.5% V-CSH-PCE, and 0.5% WTF were added, the compressive strength of the subsoil after 1 day of curing was 0.3755 MPa, which was nearly 12 times higher compared with a blank sample. Meanwhile, the leaching concentrations of Cu2+, Zn2+, Pb2+, and Cr3+ in the substrate were 2.52, 1.12, 1.32, and 0.51 mg/L, respectively, which were lower than the leaching standard of “Hazardous Waste Identification Standard Leaching Toxicity Identification (GB 5085.3-2007)”. In addition, the compressive strength of the soil after 1 day of curing at a low temperature (4 °C) was 0.2915 MPa, which was 30.9% higher compared with the soil without the V-CSH-PCE. The results showed that the cement-fly ash-(V-CSH-PCE)-WTF mixture has good application prospects in improving the compressive strength of soil and stabilizing heavy metal ions.

The soil investigated for suitability checks, as a subgrade material in this study, was a crude oil contaminated (COC) soil treated using an electrokinetic technique. The index properties and compaction characteristics of the electrokinetic remediated (EKR) soil are natural moisture content was 10.97%; The Atterberg limit test showed liquid limit, plastic limit, plasticity index and linear shrinkage of 36.50%, 22.05%,14.45 %, and 4.30%, respectively. The percentage of 62.80% passes 0.075mm sieve with a maximum dry density (MDD) of 1.77 Mg/m3, and the moisture content decreased from 13.2% to 11.81%. The soil is classified as A-6 according to AASHTO classification system and belong to clay of low plasticity CL or OL group according to the Unified Soil Classification System. The unconfined compression strength, (UCS), durability, and California bearing ratio (CBR) of the electrokinetic remediated soil improved marginally from 46.63kN/m2 to 92.64kN/m2; from 18% to 23%; and from 2.55% to 4.05% respectively. However, these results obtained, do not meet the minimum requirement of the Nigerian General Specification. As a result, it is advised for further research, that an EKR soil be stabilized using cement stabilization to achieve the desired subgrade strength.

In order to study the improvement effect of nano-clay and polypropylene fiber on the mechanical properties of recycled aggregates, unconfined compression tests and triaxial shear tests were conducted. The experimental results show that adding polypropylene fibers to recycled aggregates increases the unconfined compressive strength by 27% and significantly improves ductility. We added 6% nano-clay to fiber-reinforced recycled aggregates, which increased the unconfined compressive strength of the recycled aggregates by 49% and the residual stress by 146%. However, the ductility decreased. Under low confining pressures, with the addition of nano-clay, the peak deviatoric stress strength of the fiber-reinforced recycled aggregates first decreased and then increased. When the nano-clay content was 8%, this reached a maximum value. However, under high confining pressures, the recycled aggregate particles were tightly interlocked, so that the improvement effect of the fiber and nano-clay was not obvious. As more nano-clay was added, the friction angle of the fiber-reinforced recycled aggregates decreased, while the cohesion increased. When the content of nano-clay was 8%, the cohesive force increased by 110%. The results of this research indicate that adding both polypropylene fibers and nano-clay to recycled aggregates has a better improvement effect on their strength characteristics than adding only polypropylene fibers. This study can provide a reference for improving the mechanical properties of recycled aggregates and the use of roadbeds. [ABSTRACT FROM AUTHOR]

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Copyright of Bulletin of the Chinese Ceramic Society is the property of Bulletin of the Chinese Ceramic Society Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The properties of the improved soil are closely related to the properties of the improved materials added, and the curing process is the key process to make the performance of the improved materials play. In this paper, several groups of improvement tests on sandy soil were carried out, and the improved sand was placed under different curing conditions (standard curing, water curing, air drying curing, dry and wet cycle curing) to explore the improvement effects of each material under different curing conditions. Cement (6 %, 8 %, 12 %, 16 %), active magnesium oxide (4 %, 8 %, 12 %, 16 %), polyvinyl alcohol solution (PVA)(6 %, 8 %, 12 %, 16 %) and polypropylene fiber (PPF)(0.25 %, 0.5 %, 1 %, 2 %) were used as modified materials. The improvement effect was evaluated by unconfined compressive strength, stress-strain curve and scanning electron microscope observation of internal cementation state. The results show that the improved material has different effects under different curing conditions when the same material is added to the improved soil. The improvement effects of cement, active magnesium oxide, PVA and PPF on sand are all affected by curing conditions. Among them, cement improved sand is suitable for standard curing corresponding to cement. Activated MgO can obtain a higher strength of 2.7 MPa under dry and wet cycle curing. PVA modified sand has almost no strength under standard curing conditions, but can reach 0.9 MPa under dry curing conditions. The unconfined compressive strength of fiber-modified sand decreases with the increase of water content. The SEM results showed that the improved material strengthened by hydration reaction could form dense hydration products and fill the pores between the sand grains under appropriate curing conditions, while the reaction was incomplete or overreacted under other curing conditions, leading to the defects of the sample.

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It can effectively shorten the construction period, improve the use of solid wastes and reduce carbon emissions by using the new type of low carbon geopolymer cementing material to replace ordinary high energy consumption and high consumption cement to solidify dredged silt. With mineral powder, fly ash and metakaolin are used as composition cementitious materials, and sodium silicate as activator to prepare low carbon geopolymer solidified dredged silt, an experiment and analysis of the unconfined compressive strength and compressive property of geopolymer solidified dredged silt were carried out. The results show that the combination of mineral powder and metakaolin makes up for the low early activity of fly ash. Compared with the solidified silt with 10% cement content, the unconfined compressive strength of geopolymer solidified soil with 3.5% mineral powder, 3.5% fly ash and 3% metakaolin increases by 244.1% for 7 d. The stress-strain curve shows obvious stress peaks. The carbon emission is only 15% of that of traditional cement. It has good ecological benefits and broad application prospects. The research results can provide reference for large-scale and rapid solidification disposal of dredged silt. [ABSTRACT FROM AUTHOR]

The undrained shear strength (Su) and cohesion (Cu) of cohesive soils are frequently determined using an unconfined compression test. However, the test results are heavily dependent on specimen size. This causes uncertainty in geotechnical analyses, constitutive models, and designs by overestimating or underestimating the shear strength of cohesive soils. Therefore, the study aims to assess the effect of the height-to-diameter ratio on the unconfined compressive strength (UCS) of cohesive soil. The soil specimen was tested on a compacted cylindrical specimen at the maximum dry density and optimum moisture content with a height to diameter (H/D) ratio of 1–3 for 38, 50, and 100 mm specimen diameters. Disturbed sample specimens were considered for the laboratory program. Accordingly, the standard Proctor compaction test determines soil classification and compaction characteristics. The unconfined compression test was performed for undisturbed and compacted remolded states of various diameters of cohesive soil specimens to investigate the strength variation with the specimen variation in H/D ratio. The laboratory test results revealed that cohesive soil's unconfined compression strength value drops rapidly with height-to-diameter ratios and the soil specimens’ diameter increases. However, the UCS value was stable at H/D ratio from 1.75 to 2.25. As the specimens’ diameter and H/D ratio increased, the peak UCS value axial strain decreased. Similarly, the gap between the axial strains of peak UCS value for the smallest and the most significant H/D ratio decreased with increase in the specimens’ diameter.

Transportation infrastructures are in an accelerated development process worldwide, occasionally in a process of rehabilitation, in both cases investments are strongly depending on the subgrade mechanical behavior that is often requiring a soil improvement by stabilization where eco-materials would be the first choice. The objective of this paper is to investigate the influence of the curing time on soil stabilization with eco-cement (EC) compared to Portland cement (PC) as stabilizers. Standard procedure has been used to obtain the soil-cement mixed samples with 2.5%, 5%, 7.5% and 10% EC and PC, reported to the dry unit weight of soil, and cured for 1, 7, 14 and 28 days. After each specified curing time, compressibility and unconfined compression tests have been performed and the results of the soil modulus and strength are reported to the standard time intervals with the displayed trends beyond 28 days of curing. The unconfined compressive strength is 15% higher for EC compared to PC for 2.5% participation, increasing to 23% for 10% participation. In addition to this finding, as cement participation is referring to a large range of values, the reported values in this paper can be used as reference for soil stabilization reported on one marginal soils category, namely hard clayey soils, that exhibit a water-induced collapsibility in its natural state, improved with a new eco-cement available since 2021 for the construction industry. [ABSTRACT FROM AUTHOR]

The impact of natural sodium bentonite on the microstructure, permeability and strength characteristics of bentonite-modified loess (BML) were evaluated by scanning electron microscope (SEM) test, triaxial flexible wall permeability test, uniaxial compression test and direct shear tests. The experimental results indicate that bentonite can be used for loess solidification attributed to its effective particle filling, water absorption and expansion characteristics. The quantitative parameters of SEM images such as the average pore area, width, length and surface porosity of BML declined first and then increased with bentonite content, and the lowest was observed at a bentonite content of 15%. The hydraulic conductivity of BML declined with increasing bentonite content and was lower than the maximum allowable limit of 1.0 × 10−9 m/s. The uniaxial compressive strength and shear strength parameters of BML increased initially and subsequently declined as bentonite content increased. A normalized prediction model was established for modified loess based on the correlation between mechanical characteristics and the microscopic pore parameters, which was verified to be rational in estimating the macro- and micro-scale properties of BML. Therefore, when the anti-seepage landfill layers are constructed in the Loess Plateau area, 15% of bentonite is recommended in modified loess, which has optimal impermeability and mechanical properties. [ABSTRACT FROM AUTHOR]

The earliest method of waste disposal is dumping waste in landfills. The important component of landfills which prevents the passage of leachate to the subsoil is defined as the bottom liner. A landfill liner must contain a specific range in terms of swelling behavior, strength, and permeability before placing down beneath the constructed landfills. The present paper summarizes the detail of the different materials and their feasibility which satisfy the criteria to be used as landfills liner. The detail of findings of microstructural analysis (SEM–EDX, XRD, FT-IR, etc.) along with the waste materials which compact the particles and enhance the strength and stability of soils is also discussed. A lot of landfill liner materials such as Bentonite, sand, fly ash, cement, biochar, marine clay, lateritic soil, and geosynthetics have been used to enhance the geotechnical properties of liners. Among all, geosynthetic clay liner (GCL) and compacted clay liner (CCL) show increased hydraulic conductivity for clay soil with high plasticity whereas this value reduces for clayey soil having low plasticity with the increase in the concentration of the salt solution. The hydraulic conductivity of the mix containing biochar, bentonite, and sand is found to be 1 × 10−9 m/s. The hydraulic conductivity and shear strength of the soil increases while the compressibility of the soil decreases with an increase in the biochar percentage having smaller particle size. Also, the alkaline activator is suggested to be best for soil stabilization as compared to standard Portland cement. The development of new materials must be environmentally sustainable and should contain sufficient shear strength so that it can sustain the overburdened load of dumped waste. It should also be free from cracking so that the contamination of subsoil and groundwater can be minimized. [ABSTRACT FROM AUTHOR]

The cement composite calcium lignosulfonate is used to enhance the mechanical properties and the freeze–thaw resistance of loess. Based on an unconfined compressive test under different freeze–thaw cycles, the influence of cement dosage, curing age, and freeze–thaw cycles on compressive strength are discussed. The results indicate that the strength of loess can increase by up to 13 times, and the loss of strength is reduced from 72% to 28% under the reinforcement of cement dosage and curing age. The loss of strength is mainly concentrated in the initial 5 freeze–thaw cycles, and the structure gradually stabilizes after 10 freeze–thaw cycles. In addition, according to the X-ray diffraction test, it is found that the stabilized loess exhibits a comparatively more stable mineral composition. The scanning electron microscope results reveal that hydration products enveloped the soil particles, forming a mesh structure that strengthens the connection between the soil particles. The freeze–thaw damage makes the small and medium pores turn into large pores in loess, while the stabilized loess changes micro and small pores into small and medium pores, with no large pores found. It is feasible to improve loess with the cement composite calcium lignosulfonate, which can provide references for the reinforcement treatment of loess.

In this work, a series of unconfined compression tests at different water contents were performed to investigate the mechanical behaviour of clay–sand mixtures compacted in standard Proctor conditions. For studying the effect of water content and suction on unconfined compressive strength (UCS) and on strain secant modulus (E50 modulus) of these mixtures, drying–wetting paths were defined by measuring the soil–water characteristic curves (SWCCs) using osmotic and salt solution techniques and filter paper method. The results highlighted that an increase in sand content of the mixture leads to an increase in the maximum dry densities and a decrease in the optimum water content of the materials. However, at the given state, when clay is mixed with 25% of sand, the UCS and E50 modulus increase to 37% and 70%, respectively, compared to those of clayey samples. But when clay is mixed with 50% of sand, the UCS and E50 modulus decrease to 38% and 46%, respectively, compared to those of clayey samples. The results also indicate that the UCS and E50 increase with a decrease in the water content and an increase in suction, irrespective of the sand content.

Kuttanad region in Kerala, India, is a place that predominantly consists of soft soil formations with low shear strength and low water resistance rendering them problematic for construction purposes. Pavements constructed on such soft deposits have been subjected to structural rutting and the high erodibility of the in-situ soil necessitates the need to use suitable ground improvement techniques. The present environmental scenario demands the implementation of sustainable techniques for ground rejuvenation and effective stabilizers for enhancing engineering properties. This study investigates the amelioration of Kuttanad soft soil using chitosan as a soil amendment to improve its durability and erodibility characteristics. The untreated and chitosan-treated samples were exposed to 5 h of wetting cycle followed by 43 h of drying cycles until their failure. The unconfined compressive strength (UCS) of samples prepared with different dosages (0.5, 2, 4%) and cured for 14, 28, 60, and 90 days was evaluated at the onset and after each drying cycle to measure their durability index. Kuttanad soil was amended with 2% and cured for 90 days withstood five cycles with a UCS of more than 1,000 kPa. The drip erosion tests were used to check the erodibility performance for the aforementioned different dosages and curing periods. The 2% and 4% chitosan amended samples resisted the entire test duration of 10 min indicating the highest water erosion resistance. The findings of the current study evaluated through durability and erosion tests reinforced the effectiveness of chitosan as an effective biopolymer for soft soils subjected to constant water attack and can be easily implemented in places with such vulnerability. A typical earthen canal lining amended with chitosan reduced the carbon emissions by 8.74 and 7.44 times compared to conventional amendments like lime and cement in Carbon Footprint Analysis.