Evaluating the stabilized lead(Pb)-contaminated soils through sampling and laboratory testing involves costly and time-consuming processes.Therefore,this study employed a low-cost and non-destructive resistivity tool ...Evaluating the stabilized lead(Pb)-contaminated soils through sampling and laboratory testing involves costly and time-consuming processes.Therefore,this study employed a low-cost and non-destructive resistivity tool to evaluate the Pb-contaminated soils stabilized by electrolytic manganese residue(EMR)-based geopolymer(EG-OPC)from the strength and environmental benefits perspective.First,unconfined compressive strength(UCS)and leaching tests were conducted to study the stabilization effectiveness of EG-OPC.Results indicated that the UCS values of soil(5000 mg/kg of pollutants)stabilized by 20%EG-OPC were 4.87 MPa and 8.13 MPa after 7 d and 60 d of curing,respectively.After 60 d of curing,the Pb concentration in the leachate reached 44 mg/L,far lower than the control group(321 mg/L).Second,soil,pore water,and leachate resistivity(ERS,ERW,and ERL)were measured to establish fitting relationships with strength parameters and pollution risk.The good fitting results(e.g.ERS/ERW versus UCS/secant modulus(E50):correlation coefficient R2 z 0.9,ERS/ERW versus Pb contents:R2 z 0.9,and ERL versus Pb2þconcentration:R2¼0.92)and well used Archie's law(ERS versus ERW:R2>0.9)indicate that the resistivity can be used to evaluate the stabilization effectiveness.Furthermore,the microscopic results revealed two behaviors,demonstrating the reliability of resistivity:(1)with the hydration process,resistivity increases due to a denser structure and lower amounts of free water and Pb ions,and(2)the addition of Pb reduces resistivity due to its inhibition or even destructive effects on cementation and formation of hydration products.展开更多
In the field of soil stabilization, only calcium silicate hydrate(CSH) and ettringite(AFt) as hydration products have been reported to directly contribute to the strength enhancement of the soil. A chloride dredger fi...In the field of soil stabilization, only calcium silicate hydrate(CSH) and ettringite(AFt) as hydration products have been reported to directly contribute to the strength enhancement of the soil. A chloride dredger fill, an artificial chloride saline soil, and a non-saline soil were stabilized by Portland cement(PC) and PC with Ca(OH)_2(CH) with different contents. A series of unconfined compressive strength(UCS) tests of stabilized soil specimen after curing for 7 d and 28 d were carried out, and the hydration products and microstructure of the specimens were observed by X-ray diffractometry(XRD), scanning electronic microscopy(SEM), and energy-dispersive X-ray analysis(EDXA). The results showed that the strengths of PC+CH-stabilized chloride saline soils were much higher than those of PC-stabilized soils. A new hydration product of calcium aluminate chloride hydrate, also known as Friedel's salt, appeared in the PC+CH-stabilized chloride saline soils. The solid-phase volume of Friedel's salt expanded during the formation of the hydrate; this volume filled the pores in the stabilized soil. This pore-filling effect was the most important contribution to the significantly enhanced strength of the PC+CH-stabilized chloride saline soils. On the basis of this understanding, a new optimized stabilizer was designed according to the concept that the chloride in saline soil could be utilized as a component of the stabilizer. The strength of the chloride saline soils stabilized by the optimized stabilizer was even further increased compared with that of the PC+CH-stabilized soils.展开更多
In order to improve the engineering properties oforganic soil, a new stabilization agent is developed by theaddition of phosphor gypsum and calcium aluminate cement.The artificial organic soil is applied in the study ...In order to improve the engineering properties oforganic soil, a new stabilization agent is developed by theaddition of phosphor gypsum and calcium aluminate cement.The artificial organic soil is applied in the study and a series oflaboratory tests were carried out to explore new stabilizationagents and determine the optimal dosage. Unconfinedcompressive strength （UCS） and the pH value of soil poresolution were measured. The influence of organic content,agent composition and curing time on the UCS of sampleswere also researched. The test results show that the UCS ofstabilized organic soils by a new agent achieves approximately800 and 1 200 kPa at 28 and 90 d curing time, respectively.The pH test results show that a high alkaline environment is anecessary and not a sufficient condition for high strength. Thestrength of stabilized soil is related to the hydration product ofstabilization agent. The mechanism of strength formation wasalso explored by X-ray diffraction （XRD）, mercury intrusionporosimetry （MIP） and scanning electron microscope （SEM）tests. A large amount of ettringite is produced to fill the largepores of organic soils, which contribute to the high UCS valueof stabilized organic soils. The new agent can solidify theorganic soil successfully as well as provide a new approach totreat the organic soil.展开更多
To accelerate the early strength of lime-flyush stabilized soil for extending its further uses in highway and shortening highway constraction time, five kinds of chemical odditives were chosen on the basis of mechanis...To accelerate the early strength of lime-flyush stabilized soil for extending its further uses in highway and shortening highway constraction time, five kinds of chemical odditives were chosen on the basis of mechanism analysis of accelerating early strength in highway as a semi-rigid base materhd, and a series of experiments about the effect of differeat kinds of additives and quantity on the early strength of the stabilized soll were tested. The results show that chemical additives can efftciently improve the early strength of lime-flyush stabilized soil both the 7 d and 28d, and the optimum quantity for above chemical additive is 1.5%-2.5% approximately. Some suggestions for the practical construction were also proposed.展开更多
This paper studies the microstructure variation induced by super-absorbent polymer(SAP)to understand the mechanism of macroscopic strength improvement of stabilized soil.The fabric changes of cement elime stabilized s...This paper studies the microstructure variation induced by super-absorbent polymer(SAP)to understand the mechanism of macroscopic strength improvement of stabilized soil.The fabric changes of cement elime stabilized soil were analyzed with respect to the variation of SAP content,water content,lime content and curing time,using mercury intrusion porosimetry(MIP)tests.It can be observed that the delimitation pore diameter between inter-and intra-aggregate pores was 0.2 mm for the studied soil,determined through the intrusion/extrusion cycles.Experimental results showed that fabric in both inter-and intra-aggregate pores varied significantly with SAP content,lime content,water content and curing time.Two main changes in fabric due to SAP are identified as:(1)an increase in intra-aggregate pores(<0.2 mm)due to the closer soilecementelime cluster space at higher SAP content;and(2)a decrease in inter-aggregate pores represented by a reduction in small-pores(0.2e2 mm)due to the lower pore volume of soil mixture after water absorption by SAP,and a slight increase in large-pores(>2 mm)due to the shrinkage of SAP particle during the freezeedry process of MIP test.Accordingly,the strength gain due to SAP for cementelime stabilized soil was mainly due to a denser fabric with less interaggregate pores.The cementitious products gradually developed over time,leading to an increase in intra-aggregate pores with an increasing proportion of micro-pores(0.006e0.2 mm).Meanwhile,the inter-aggregate pores were filled by cementitious products,resulting in a decrease in total void ratio.Hence,the strength development over time is attributable to the enhancement of cementation bonding and the refinement of fabric due to the increasing cementitious compounds.展开更多
This study attempted to investigate the potential of sugarcane press mud(PM) as a secondary additive in conjunction with lime for the stabilization of an expansive soil.The physico-mechanical properties of an expansiv...This study attempted to investigate the potential of sugarcane press mud(PM) as a secondary additive in conjunction with lime for the stabilization of an expansive soil.The physico-mechanical properties of an expansive soil,such as plasticity,shrink-swell behavior,unconfined compressive strength(UCS),mineralogical and microstructural characteristics were investigated.The expansive soil was stabilized at its optimum lime content(7%) for producing maximum strength,and was modified with four different quantities of PM in small dosages(0.25%-2%).Cylindrical soil samples,38 mm in diameter and 76 mm in height,were cast and cured for varying periods to evaluate the strength of the amended soil.The spent samples after strength tests were further used for determination of other properties.The test results revealed that PM modification led to a substantial improvement in 7-d strength and noticeable increase in 28-d strength of the lime-stabilized soil(LSS).The addition of PM does not cause any detrimental changes to the shrink-swell properties as well as plasticity nature of the stabilized soil,despite being a material of organic origin.Mineralogical investigation revealed that the formation of calcium silicate hydrate(CSH) minerals,similar to that of pure lime stabilization with only the type of mineral varying due to the modification of PM addition,does not significantly alter the microstructure of the LSS except for superficial changes being noticed.展开更多
This study investigates the innovative reuse of sewage sludge with eco-friendly alkaline solutes to improve clayey soil without conventional cementitious binders.The unconfined compressive strength(UCS)was the main cr...This study investigates the innovative reuse of sewage sludge with eco-friendly alkaline solutes to improve clayey soil without conventional cementitious binders.The unconfined compressive strength(UCS)was the main criterion to assess the quality and effectiveness of the proposed solutions,as this test was performed to measure the strength of the stabilized clay by varying binders’dosages and curing times.Moreover,the direct shear test(DST)was used to investigate the Mohr-Coulomb parameters of the treated soil.Microstructure observations of the natural and treated soil were conducted using scanning electron microscope(SEM),energy-dispersive spectroscopy(EDS),and FTIR.Furthermore,toxicity characteristic leaching procedure(TCLP)tests were performed on the treated soil to investigate the leachability of metals.According to the results,using 2.5%of sewage sludge activated by NaOH and Na_(2)SiO_(3)increases the UCS values from 176 kPa to 1.46 MPa after 7 d and 56 d of curing,respectively.The results of the DST indicate that sewage sludge as a precursor increases cohesion and enhances frictional resistance,thereby improving the Mohr-Coulomb parameters of the stabilized soil.The SEM micrographs show that alkali-activated sewage sludge increases the integrity and reduces the cavity volumes in the stabilized soil.Moreover,TCLP tests revealed that the solubility of metals in the treated soil alkaliactivated by sewage sludge significantly decreased.This study suggests that using sewage sludge can replace cement and lime in ground improvement,improve the circular economy,and reduce the carbon footprint of construction projects.展开更多
Clayey soils in Syria cover a total area of more than 20,000 km2 of the country,most of which are located in the southwestern region.In many places of the country,the clayey soils caused severe damage to infrastructur...Clayey soils in Syria cover a total area of more than 20,000 km2 of the country,most of which are located in the southwestern region.In many places of the country,the clayey soils caused severe damage to infrastructures.Extensive studies have been carried out on the stabilization of clayey soils using lime.Syria is rich in both lime and natural pozzolana.However,few works have been conducted to investigate the influence of adding natural pozzolana on the geotechnical properties of lime-treated clayey soils.The aim of this paper is to understand the effect of adding natural pozzolana on some geotechnical properties of lime-stabilized clayey soils.Natural pozzolana and lime are added to soil within the range of 0%–20%and 0%–8%,respectively.Consistency,compaction,California bearing ratio(CBR)and linear shrinkage properties are particularly investigated.The test results show that the investigated properties of lime-treated clayey soils can be considerably enhanced when the natural pozzolana is added as a stabilizing agent.Analysis results of scanning electron microscopy(SEM)and energy-dispersive X-ray spectroscopy(EDX)show significant changes in the microstructure of the treated clayey soil.A better flocculation of clayey particles and further formation of cementing materials in the natural pozzolana-lime-treated clayey soil are clearly observed.展开更多
The suitability of using precipitated silica(PS) from the burning of rice husk was investigated to improve the geotechnical engineering properties of a black cotton soil. A laboratory experimental program consisting o...The suitability of using precipitated silica(PS) from the burning of rice husk was investigated to improve the geotechnical engineering properties of a black cotton soil. A laboratory experimental program consisting of series of specific gravity, Atterberg limits, compaction, California bearing ratio(CBR), unconfined compression and consolidation tests was conducted on the untreated and PS treated soil samples. The application of PS to the soil significantly changed its properties by reducing its plasticity and making it more workable, improving its soaked strength, and increasing its permeability and the rate at which the soil gets consolidated. An optimal PS content of 50%, which provided the highest soaked strength, is recommended for the improvement of the subgrade characteristics of the BC soil for use as a pavement layer material.展开更多
Solidification/stabilization （S/S） is one of the most effective methods of dealing with heavy metal contaminated soils. The effects of cyclic wetting and drying on solidified/stabilized contaminated soils were inves...Solidification/stabilization （S/S） is one of the most effective methods of dealing with heavy metal contaminated soils. The effects of cyclic wetting and drying on solidified/stabilized contaminated soils were investigated. A series of test program, unconfined compressive strength （UCS） test, TCLP leaching test and scanning electron microscopy （SEM） test, were performed on lead and zinc contaminated soils solidified/stabilized by fly ash. Test results show that UCS and the leaching characteristics of heavy metal ions of S/S contaminated soils are significantly improved with the increase of fly ash content. UCS of S/S soils firstly increases with the increase of the times of drying and wetting cycles, after reaching the peak, it decreases with it. When the pollutant content is lower （1 000 mg/kg）, the TCLP concentration first slightly decreases under cyclic drying and wetting, then increases, but the change is minor. The TCLP concentration is higher under a high pollutant content of 5 000 mg/kg, and increases with the increase of the times of drying and wetting cycles. The results of scanning electron microscopy （SEM） test are consistent with UCS tests and TCLP leaching tests, which reveals the micro-mechanism of the variations of engineering properties of stabilized contaminated soils after drying and wetting cycles.展开更多
In order to investigate the effect o f some factors on the unconfined compressive strength(UCS)for composite soil stabilizer-stabilized gravel soil(CSSSGS),the orthogonal test is adopted to set up the experimental sch...In order to investigate the effect o f some factors on the unconfined compressive strength(UCS)for composite soil stabilizer-stabilized gravel soil(CSSSGS),the orthogonal test is adopted to set up the experimental scheme.Three levels o f each factor armconsidered to obtain the change laws o f UCS,in which the binder dosages are8%,10%,and12%;the curing times ae7,14and21d;the gradation nae0.3,0.35and0.4;and the degrees of compaction are95%,97%,and99%.The range analysis clearly indicates that the influence degree o f the four factors on UCS is in such an order:dosage,age,gradation,and degree o f compaction.The variance analysis shows that only the composite soil stabilizer dosage can significantly affect UCS.In road construction,the examination o f composite soil stabilizer dosage and base-course maintenance should be given much more attention to obtain satisfactory base-course strength,compared w ith gradation floating and the change of degree o f compaction.展开更多
The warm and ice-rich frozen soil is characterized by high unfrozen water content, low shear strength and large compressibility, which is unreliable to meet the stability requirements of engineering infrastructures an...The warm and ice-rich frozen soil is characterized by high unfrozen water content, low shear strength and large compressibility, which is unreliable to meet the stability requirements of engineering infrastructures and foundations in permafrost regions. In this study, a novel approach for stabilizing the warm and ice-rich frozen soil with sulphoaluminate cement was proposed based on chemical stabilization. The mechanical behaviors of the stabilized soil, such as strength and stress-strain relationship, were investigated through a series of triaxial compression tests conducted at -1.0℃, and the mechanism of strength variations of the stabilized soil was also explained based on scanning electron microscope test. The investigations indicated that the strength of stabilized soil to resist failure has been improved, and the linear Mohr-Coulomb criteria can accurately reflect the shear strength of stabilized soil under various applied confining pressure. The increase in both curing age and cement mixing ratio were favorable to the growth of cohesion and internal friction angle. More importantly, the strength improvement mechanism of the stabilized soil is attributed to the formation of structural skeleton and the generation of cementitious hydration products within itself. Therefore, the investigations conducted in this study provide valuable references for chemical stabilization of warm and ice-rich frozen ground, thereby providing a basis for in-situ ground improvement for reinforcing warm and ice-rich permafrost foundations by soil-cement column installation.展开更多
In recent years,there has been growing interest in developing methods for mitigating greenhouse effect,as greenhouse gas emissions continue to contribute to global temperature rise.On the other hand,investigating geop...In recent years,there has been growing interest in developing methods for mitigating greenhouse effect,as greenhouse gas emissions continue to contribute to global temperature rise.On the other hand,investigating geopolymers as environmentally friendly binders to mitigate the greenhouse effect using soil stabilization has been widely conducted.However,the effect of CO_(2)exposure on the mechanical properties of geopolymer-stabilized soils is rarely reported.In this context,the effect of CO_(2)exposure on the mechanical and microstructural features of sandy soil stabilized with volcanic ash-based geopolymer was investigated.Several factors were concerned,for example the binder content,relative density,CO_(2)pressure,curing condition,curing time,and carbonate content.The results showed that the compressive strength of the stabilized sandy soil specimens with 20%volcanic ash increased from 3 MPa to 11 MPa.It was also observed that 100 kPa CO_(2)pressure was the optimal pressure for strength development among the other pressures.The mechanical strength showed a direct relationship with binder content and carbonate content.Additionally,in the ambient curing(AC)condition,the mechanical strength and carbonate content increased with the curing time.However,the required water for carbonation evaporated after 7 d of oven curing(OC)condition and as a result,the 14-d cured samples showed lower mechanical strength and carbonate content in comparison with 7-d cured samples.Moreover,the rate of strength development was higher in OC cured samples than AC cured samples until 7 d due to higher geopolymerization and carbonation rate.展开更多
A comprehensive understanding of aggregate dynamics is the foundation for establishing sustainable sugarcane production systems,especially in vulnerable red soil ecosystems.While existing studies have established a ba...A comprehensive understanding of aggregate dynamics is the foundation for establishing sustainable sugarcane production systems,especially in vulnerable red soil ecosystems.While existing studies have established a basic understanding of aggregate formation and stabilization,the functional relationship between aggregate stability and erosion resistance under extended sugarcane monoculture remains inadequately characterized.We employed an integrated methodology combining dry/wet sieving,the Le Bissonnais method and scanning electron microscopy to quantitatively evaluate the soil aggregate stability and erosion resistance across six distinct cultivation chrono-sequences(3–32 years)and two soil depths(0–15 cm and 15–30 cm)in the sugarcane cultivation area of Qingshui Village,Wuxuan County,Guangxi Zhuang Autonomous Region,China,aiming at providing insights for developing soil conservation strategies in sugarcane cultivation systems.The results reveal three core findings.First,planting years significantly influence the proportions of soil aggregates with varying particle sizes.Under the treatments with Le Bissonais methods,the mean weight diameter(MWD)under fast wetting,disturbance after pre-wetting,and slow wetting decrease with increasing planting years,while the relative dissipation index,relative mechanical fragmentation index,and erodibility factor(K)exhibit varying degrees of change,indicating progressive soil structural degradation and increased erosion susceptibility.Second,long-term sugarcane monocropping leads to declining soil organic carbon,liquid limit,plastic limit,and clay content,likely due to factors such as soil-forming materials and rainfall.Concurrently,the increased sand content and porosity weaken interparticle bonding and reducing aggregate stability over time.Third,correlation analysis demonstrates that MWD and geometric mean diameter(GMD)under disturbance after pre-wetting and slow wetting treatments show strong positive correlations with soil organic carbon,p H,clay content,liquid limit,and plastic limit but negative correlations with sand content,total porosity,and capillary porosity.Furthermore,K is significantly negatively correlated with soil physicochemical properties as well as GMD and MWD.These results help us understand the mechanism of aggregate stability variation in sugarcane-cultivated red soils and support the development of soil conservation strategies for sustaining sugarcane productivity in subtropical regions.展开更多
The present study investigates the engineering properties of submerged organic silt(orSi)stabilized with F-class fly ash(FA),with and without the addition of an activator(CaO).The utilization of F-class FA for soil im...The present study investigates the engineering properties of submerged organic silt(orSi)stabilized with F-class fly ash(FA),with and without the addition of an activator(CaO).The utilization of F-class FA for soil improvement is an important aspect of sustainable and environmentally-conscious geotechnical engineering when marginal usage of lime and concrete is of great interest to engineers and societies.Currently,discussion is predominantly focused on the positive aspects of using the F-class FA,with a paucity of emphasis on the negative aspects.To explore these features more thoroughly,a series of strength and compressibility tests was conducted.The sample preparation and curing methodology were chosen to replicate the in situ conditions where soil is surcharged and submerged in water.It was found that the incorporation of F-class FA without an activator reduces the undrained shear strength of submerged orSi by about 20%–25%and permanently prevents any thixotropic strength restoration.An increase in undrained shear strength is observed when lime(3%–6%)is added to the soil–FA mixture or when only lime(in the same amount of 3%–6%)is used.Consequently,F-class FA can be successfully used as a filler for slurries with minimum lime content in soil mixing methods.The F-class FA(with or without an activator)shifts the so-called“creep delay”in time,consequently reducing the total creep settlements.The shift of“creep delay”is more considerable for orSi stabilized with lime or with FA and lime as an activator,than for orSi stabilized with pure F-class FA.展开更多
In response to the effectiveness of reforestation in controlling soil erosion,there has been a dramatic increase in forest coverage in the hilly red soil region of southern China.Aggregate stability and soil shear str...In response to the effectiveness of reforestation in controlling soil erosion,there has been a dramatic increase in forest coverage in the hilly red soil region of southern China.Aggregate stability and soil shear strength are indicators that reflect soil resistance to erosion and its ability to prevent shallow landslides,respectively.However,limited research has focused on the response of soil aggregate stability and shear strength to reforestation.We selected three types of reforestations(Phyllostachys edulis forest,Cunninghamia lanceolata(Lamb.)Hook.forest,Citrus sinensis(L.)Osbeck.orchard),a natural forest(mixed coniferous and broadleaf forests),and a fallow land as study plots,and measured root traits,and soil physicochemical traits,i.e.,pH,soil organic matter(SOC),Soil water content(SWC),soil bulk density(BD),soil cohesion(c),soil internal friction angle(φ)and analyzed their multiple interactions.The soil aggregate stability traits,refer to the mean weight diameter(MWD)and geometric mean diameter(GMD),exhibited a significant increase in reforested plots,approximately 200%compared to fallow land and 50%compared to natural forests.For soil shear strength the values were approximately 20%higher than in fallow land and approximately 10%lower than in natural forests.Soil aggregate stability and soil shear strength did not exhibit a significant positive correlation across all plots,and the underlying drivers of these traits were variable.For instance,in natural forest and timber stands,soil aggregate stability was mainly influenced by soil organic carbon,while soil shear strength was primarily affected by root length density.In economic forest,aggregate stability and shear strength are mainly affected by organic carbon.Overall,we found that vegetation restoration enhances soil erosion resistance,however,the primary drivers for the improvement of aggregate stability(soil organic carbon)and shear strength(root length density)are different.Therefore,in future benefit assessments of vegetation restoration projects aimed at soil erosion control,different indicators should be considered based on specific conditions.展开更多
This study investigates the use of a low-carbon soil stabilizer called SDG,which is made up of granulated blast furnace slag (GGBFS),desulfurization gypsum (DG),and calcium carbide slag (CCS),to solidify the soil.The ...This study investigates the use of a low-carbon soil stabilizer called SDG,which is made up of granulated blast furnace slag (GGBFS),desulfurization gypsum (DG),and calcium carbide slag (CCS),to solidify the soil.The impact of SDG components on the strength and durability of solidified soil was analysed through a series of tests,including unconfined compressive strength,water stability coefficient,water absorption rate,drying-wetting cycles,and shrinkage tests.Furthermore,microstructure characteristics were analysed using X-ray diffraction (XRD) and scanning electron microscopy (SEM).The study shows that the solidified soil has excellent strength and durability when the SDG stabilizer contains 60% GGBGS,10% DG,and 30% CCS.Additionally,increasing the DG content negatively affects the soil's resistance to water.The SDG stabilizer has potential chemical cementitious characteristics and the calcium carbide slag is rich in calcium ions,which undergo an ion exchange reaction with minerals in the soil.These findings offer new ideas for the development of soil stabilizers.展开更多
We read with great interest the investigations conducted by Pourakbar et al.(2024)on the“Stabilization of clay soil using alkali-activated sewage sludge.”The authors have investigated the feasibility of utilizing al...We read with great interest the investigations conducted by Pourakbar et al.(2024)on the“Stabilization of clay soil using alkali-activated sewage sludge.”The authors have investigated the feasibility of utilizing alkali-activated sewage sludge(AASS)as a binder for stabilizing the clayey soil.Sewage sludge(SS)in varying proportions of 1.5%,2%,2.5%,3.5%,and 4.5%was utilized to prepare geopolymer binders using sodium and potassium-based alkali activators.Furthermore,unconfined compressive strength(UCS)and direct shear tests were conducted to examine the strength development of clayey soil stabilized with AASS.While the study presented some intriguing results,we have identified critical concerns regarding(i)the selection of SS as a precursor for alkali activation,(ii)technical inconsistencies associated with the compaction characteristics and microstructural analysis,and(iii)the feasibility of the proposed methodology for practical applications.Through our discussion,we seek to highlight these issues and provide constructive feedback to advance the understanding of alkali activation processes and their implications for soil stabilization.展开更多
oil aggregates profoundly impact soil sustainability and crop productivity, and they are influenced by complexinteractions between minerals and organics. This study aimed to elucidate the alterations in mineralogy and...oil aggregates profoundly impact soil sustainability and crop productivity, and they are influenced by complexinteractions between minerals and organics. This study aimed to elucidate the alterations in mineralogy and soilorganic carbon(SOC) following long-term green manure incorporation and the effect on soil aggregates. Based on 5-and 36-year field experiments, surface soil samples(0–20 cm) were collected from Alfisol and Ferrisol soilssubjected to rice–rice–winter fallow(CK) and rice–rice–Chinese milk vetch(MV) treatments to investigate aggregatestability, mineralogy, SOC composition, and soil microstructural characteristics. The results showed that high clay-content Ferrisol exhibited greater aggregate stability than low clay-content Alfisol. The phyllosilicates in Alfisolprimarily comprised illite and vermiculite, whereas those in Ferrisol with high-content free-form Fe oxides(Fed) weredominated by kaolinite. Additionally, the clay fraction in Ferrisol contained more aromatic-C than the clay fraction inAlfisol. The 36-year MV incorporation significantly increased the Ferrisol macroaggregate stability(9.57–13.37%),and it also facilitated the transformation of vermiculite into kaolinite and significantly increased the clay, Fed, and aromatic-C contents in Ferrisol. Backscattered electron(BSE)-scanning electron microscopy/energy dispersive X-ray spectroscopy(SEM/EDS) revealed a compact aggregate structure in Ferrisol with co-localization of Feoxides and kaolinite. Moreover, the partial least path model(PLS-PM) revealed that clay content directly improvedmacroaggregate stability, and that kaolinite and Fed positively and directly affected clay or indirectly modulated clay formation by increasing the aromatic-C levels. Overall, long-term MV incorporation promotes clay aggregation by affecting mineral transformation to produce more kaolinite and Fe oxides and retain aromatic-C, and it ultimately improves aggregate stability.展开更多
The traditional cement-based stabilization cannot effectively stabilize the marine soft clay under submerged conditions.In order to solve this problem,the enhancement of cement-stabilized marine soft clay was investig...The traditional cement-based stabilization cannot effectively stabilize the marine soft clay under submerged conditions.In order to solve this problem,the enhancement of cement-stabilized marine soft clay was investigated in this study by adding the ionic soil stabilizer(ISS)and polyacrylamide(PAM).For this purpose,varying contents of ISS and PAM(ISS-P)were added into cement-stabilized marine soft clay and subjected to curing under submerged conditions.Atterberg limits tests,direct shear tests,unconfined compression strength(UCS)tests,water-stability tests,scanning electron microscopy analysis,and X-ray diffraction analysis were carried out.The results show that using 1.8%ISS and 0.9%PAM as the optimal ratio,the cohesion,internal friction angle,UCS,and water-stability of the samples increased by 182.7%,15.4%,176.5%,and 368.5% compared to the cement-stabilized soft clay after 28 d.The increment in soil cohesion with increasing ISS-P content was more apparent than that in the internal friction angle.The combined action of ion exchange attraction and electrostatic adsorption altered the failure characteristics of the samples,resulting in localized micro-cracking and multiple failure paths.Increasing the content of ISS-P strengthened the skeletal structure of soil,reduced inter-particle spacing,and enhanced the water-stability.Additionally,ISS promotes the hydration of cement and compensates for the inhibitory effect of PAM on early cement hydration.ISS-P can effectively enhance the strength and stability of submerged cement-based stabilized marine soft clay.展开更多
基金supported by the National Key R&D Program of China(Grant No.2022YFC3901204)the Foundation for Distinguished Young Scholars of Hubei Province,China(Grant No.2021CFA096)the National Natural Science Foundation of China(Grant No.U20A20320).
文摘Evaluating the stabilized lead(Pb)-contaminated soils through sampling and laboratory testing involves costly and time-consuming processes.Therefore,this study employed a low-cost and non-destructive resistivity tool to evaluate the Pb-contaminated soils stabilized by electrolytic manganese residue(EMR)-based geopolymer(EG-OPC)from the strength and environmental benefits perspective.First,unconfined compressive strength(UCS)and leaching tests were conducted to study the stabilization effectiveness of EG-OPC.Results indicated that the UCS values of soil(5000 mg/kg of pollutants)stabilized by 20%EG-OPC were 4.87 MPa and 8.13 MPa after 7 d and 60 d of curing,respectively.After 60 d of curing,the Pb concentration in the leachate reached 44 mg/L,far lower than the control group(321 mg/L).Second,soil,pore water,and leachate resistivity(ERS,ERW,and ERL)were measured to establish fitting relationships with strength parameters and pollution risk.The good fitting results(e.g.ERS/ERW versus UCS/secant modulus(E50):correlation coefficient R2 z 0.9,ERS/ERW versus Pb contents:R2 z 0.9,and ERL versus Pb2þconcentration:R2¼0.92)and well used Archie's law(ERS versus ERW:R2>0.9)indicate that the resistivity can be used to evaluate the stabilization effectiveness.Furthermore,the microscopic results revealed two behaviors,demonstrating the reliability of resistivity:(1)with the hydration process,resistivity increases due to a denser structure and lower amounts of free water and Pb ions,and(2)the addition of Pb reduces resistivity due to its inhibition or even destructive effects on cementation and formation of hydration products.
基金Project(51008007)supported by the National Natural Science Foundation of ChinaProject(2013318J01100)supported by the Science and Technology Project of Ministry of Communications,China
文摘In the field of soil stabilization, only calcium silicate hydrate(CSH) and ettringite(AFt) as hydration products have been reported to directly contribute to the strength enhancement of the soil. A chloride dredger fill, an artificial chloride saline soil, and a non-saline soil were stabilized by Portland cement(PC) and PC with Ca(OH)_2(CH) with different contents. A series of unconfined compressive strength(UCS) tests of stabilized soil specimen after curing for 7 d and 28 d were carried out, and the hydration products and microstructure of the specimens were observed by X-ray diffractometry(XRD), scanning electronic microscopy(SEM), and energy-dispersive X-ray analysis(EDXA). The results showed that the strengths of PC+CH-stabilized chloride saline soils were much higher than those of PC-stabilized soils. A new hydration product of calcium aluminate chloride hydrate, also known as Friedel's salt, appeared in the PC+CH-stabilized chloride saline soils. The solid-phase volume of Friedel's salt expanded during the formation of the hydrate; this volume filled the pores in the stabilized soil. This pore-filling effect was the most important contribution to the significantly enhanced strength of the PC+CH-stabilized chloride saline soils. On the basis of this understanding, a new optimized stabilizer was designed according to the concept that the chloride in saline soil could be utilized as a component of the stabilizer. The strength of the chloride saline soils stabilized by the optimized stabilizer was even further increased compared with that of the PC+CH-stabilized soils.
基金The National Natural Science Foundation of Chin(No.51578148)the Project of China Communications Construction(No.2015-ZJKJ-26)the Fundamental Research Funds for the Centra Universities,the Scientific Innovation Research of College Graduates in Jiangsu Province(No.SJLX15_0062)
文摘In order to improve the engineering properties oforganic soil, a new stabilization agent is developed by theaddition of phosphor gypsum and calcium aluminate cement.The artificial organic soil is applied in the study and a series oflaboratory tests were carried out to explore new stabilizationagents and determine the optimal dosage. Unconfinedcompressive strength （UCS） and the pH value of soil poresolution were measured. The influence of organic content,agent composition and curing time on the UCS of sampleswere also researched. The test results show that the UCS ofstabilized organic soils by a new agent achieves approximately800 and 1 200 kPa at 28 and 90 d curing time, respectively.The pH test results show that a high alkaline environment is anecessary and not a sufficient condition for high strength. Thestrength of stabilized soil is related to the hydration product ofstabilization agent. The mechanism of strength formation wasalso explored by X-ray diffraction （XRD）, mercury intrusionporosimetry （MIP） and scanning electron microscope （SEM）tests. A large amount of ettringite is produced to fill the largepores of organic soils, which contribute to the high UCS valueof stabilized organic soils. The new agent can solidify theorganic soil successfully as well as provide a new approach totreat the organic soil.
文摘To accelerate the early strength of lime-flyush stabilized soil for extending its further uses in highway and shortening highway constraction time, five kinds of chemical odditives were chosen on the basis of mechanism analysis of accelerating early strength in highway as a semi-rigid base materhd, and a series of experiments about the effect of differeat kinds of additives and quantity on the early strength of the stabilized soll were tested. The results show that chemical additives can efftciently improve the early strength of lime-flyush stabilized soil both the 7 d and 28d, and the optimum quantity for above chemical additive is 1.5%-2.5% approximately. Some suggestions for the practical construction were also proposed.
基金the China Postdoctoral Science Foundation(Grant Nos.2016M600396 and 2017T100355)the Fundamental Research Funds for the Central Universities of China(Grant No.B200204001)Jiangsu Natural Resources Science and Technology Fund(Grant No.KJXM2019025)are also acknowledged.
文摘This paper studies the microstructure variation induced by super-absorbent polymer(SAP)to understand the mechanism of macroscopic strength improvement of stabilized soil.The fabric changes of cement elime stabilized soil were analyzed with respect to the variation of SAP content,water content,lime content and curing time,using mercury intrusion porosimetry(MIP)tests.It can be observed that the delimitation pore diameter between inter-and intra-aggregate pores was 0.2 mm for the studied soil,determined through the intrusion/extrusion cycles.Experimental results showed that fabric in both inter-and intra-aggregate pores varied significantly with SAP content,lime content,water content and curing time.Two main changes in fabric due to SAP are identified as:(1)an increase in intra-aggregate pores(<0.2 mm)due to the closer soilecementelime cluster space at higher SAP content;and(2)a decrease in inter-aggregate pores represented by a reduction in small-pores(0.2e2 mm)due to the lower pore volume of soil mixture after water absorption by SAP,and a slight increase in large-pores(>2 mm)due to the shrinkage of SAP particle during the freezeedry process of MIP test.Accordingly,the strength gain due to SAP for cementelime stabilized soil was mainly due to a denser fabric with less interaggregate pores.The cementitious products gradually developed over time,leading to an increase in intra-aggregate pores with an increasing proportion of micro-pores(0.006e0.2 mm).Meanwhile,the inter-aggregate pores were filled by cementitious products,resulting in a decrease in total void ratio.Hence,the strength development over time is attributable to the enhancement of cementation bonding and the refinement of fabric due to the increasing cementitious compounds.
文摘This study attempted to investigate the potential of sugarcane press mud(PM) as a secondary additive in conjunction with lime for the stabilization of an expansive soil.The physico-mechanical properties of an expansive soil,such as plasticity,shrink-swell behavior,unconfined compressive strength(UCS),mineralogical and microstructural characteristics were investigated.The expansive soil was stabilized at its optimum lime content(7%) for producing maximum strength,and was modified with four different quantities of PM in small dosages(0.25%-2%).Cylindrical soil samples,38 mm in diameter and 76 mm in height,were cast and cured for varying periods to evaluate the strength of the amended soil.The spent samples after strength tests were further used for determination of other properties.The test results revealed that PM modification led to a substantial improvement in 7-d strength and noticeable increase in 28-d strength of the lime-stabilized soil(LSS).The addition of PM does not cause any detrimental changes to the shrink-swell properties as well as plasticity nature of the stabilized soil,despite being a material of organic origin.Mineralogical investigation revealed that the formation of calcium silicate hydrate(CSH) minerals,similar to that of pure lime stabilization with only the type of mineral varying due to the modification of PM addition,does not significantly alter the microstructure of the LSS except for superficial changes being noticed.
文摘This study investigates the innovative reuse of sewage sludge with eco-friendly alkaline solutes to improve clayey soil without conventional cementitious binders.The unconfined compressive strength(UCS)was the main criterion to assess the quality and effectiveness of the proposed solutions,as this test was performed to measure the strength of the stabilized clay by varying binders’dosages and curing times.Moreover,the direct shear test(DST)was used to investigate the Mohr-Coulomb parameters of the treated soil.Microstructure observations of the natural and treated soil were conducted using scanning electron microscope(SEM),energy-dispersive spectroscopy(EDS),and FTIR.Furthermore,toxicity characteristic leaching procedure(TCLP)tests were performed on the treated soil to investigate the leachability of metals.According to the results,using 2.5%of sewage sludge activated by NaOH and Na_(2)SiO_(3)increases the UCS values from 176 kPa to 1.46 MPa after 7 d and 56 d of curing,respectively.The results of the DST indicate that sewage sludge as a precursor increases cohesion and enhances frictional resistance,thereby improving the Mohr-Coulomb parameters of the stabilized soil.The SEM micrographs show that alkali-activated sewage sludge increases the integrity and reduces the cavity volumes in the stabilized soil.Moreover,TCLP tests revealed that the solubility of metals in the treated soil alkaliactivated by sewage sludge significantly decreased.This study suggests that using sewage sludge can replace cement and lime in ground improvement,improve the circular economy,and reduce the carbon footprint of construction projects.
基金financial support of this research from Damascus University
文摘Clayey soils in Syria cover a total area of more than 20,000 km2 of the country,most of which are located in the southwestern region.In many places of the country,the clayey soils caused severe damage to infrastructures.Extensive studies have been carried out on the stabilization of clayey soils using lime.Syria is rich in both lime and natural pozzolana.However,few works have been conducted to investigate the influence of adding natural pozzolana on the geotechnical properties of lime-treated clayey soils.The aim of this paper is to understand the effect of adding natural pozzolana on some geotechnical properties of lime-stabilized clayey soils.Natural pozzolana and lime are added to soil within the range of 0%–20%and 0%–8%,respectively.Consistency,compaction,California bearing ratio(CBR)and linear shrinkage properties are particularly investigated.The test results show that the investigated properties of lime-treated clayey soils can be considerably enhanced when the natural pozzolana is added as a stabilizing agent.Analysis results of scanning electron microscopy(SEM)and energy-dispersive X-ray spectroscopy(EDX)show significant changes in the microstructure of the treated clayey soil.A better flocculation of clayey particles and further formation of cementing materials in the natural pozzolana-lime-treated clayey soil are clearly observed.
文摘The suitability of using precipitated silica(PS) from the burning of rice husk was investigated to improve the geotechnical engineering properties of a black cotton soil. A laboratory experimental program consisting of series of specific gravity, Atterberg limits, compaction, California bearing ratio(CBR), unconfined compression and consolidation tests was conducted on the untreated and PS treated soil samples. The application of PS to the soil significantly changed its properties by reducing its plasticity and making it more workable, improving its soaked strength, and increasing its permeability and the rate at which the soil gets consolidated. An optimal PS content of 50%, which provided the highest soaked strength, is recommended for the improvement of the subgrade characteristics of the BC soil for use as a pavement layer material.
基金Foundation item： Projects（41172273, 40802079, 51108288） supported by the National Natural Science Foundation of China Project（KLE-TJGE-B1106） supported by the Opening Fund of Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education （Tongji University）, China
文摘Solidification/stabilization （S/S） is one of the most effective methods of dealing with heavy metal contaminated soils. The effects of cyclic wetting and drying on solidified/stabilized contaminated soils were investigated. A series of test program, unconfined compressive strength （UCS） test, TCLP leaching test and scanning electron microscopy （SEM） test, were performed on lead and zinc contaminated soils solidified/stabilized by fly ash. Test results show that UCS and the leaching characteristics of heavy metal ions of S/S contaminated soils are significantly improved with the increase of fly ash content. UCS of S/S soils firstly increases with the increase of the times of drying and wetting cycles, after reaching the peak, it decreases with it. When the pollutant content is lower （1 000 mg/kg）, the TCLP concentration first slightly decreases under cyclic drying and wetting, then increases, but the change is minor. The TCLP concentration is higher under a high pollutant content of 5 000 mg/kg, and increases with the increase of the times of drying and wetting cycles. The results of scanning electron microscopy （SEM） test are consistent with UCS tests and TCLP leaching tests, which reveals the micro-mechanism of the variations of engineering properties of stabilized contaminated soils after drying and wetting cycles.
基金The National Natural Science Foundation of China(No.51108081)
文摘In order to investigate the effect o f some factors on the unconfined compressive strength(UCS)for composite soil stabilizer-stabilized gravel soil(CSSSGS),the orthogonal test is adopted to set up the experimental scheme.Three levels o f each factor armconsidered to obtain the change laws o f UCS,in which the binder dosages are8%,10%,and12%;the curing times ae7,14and21d;the gradation nae0.3,0.35and0.4;and the degrees of compaction are95%,97%,and99%.The range analysis clearly indicates that the influence degree o f the four factors on UCS is in such an order:dosage,age,gradation,and degree o f compaction.The variance analysis shows that only the composite soil stabilizer dosage can significantly affect UCS.In road construction,the examination o f composite soil stabilizer dosage and base-course maintenance should be given much more attention to obtain satisfactory base-course strength,compared w ith gradation floating and the change of degree o f compaction.
基金supported by the National Natural Science Foundation of China (No. 41471062, No. 41971085, No. 41971086)。
文摘The warm and ice-rich frozen soil is characterized by high unfrozen water content, low shear strength and large compressibility, which is unreliable to meet the stability requirements of engineering infrastructures and foundations in permafrost regions. In this study, a novel approach for stabilizing the warm and ice-rich frozen soil with sulphoaluminate cement was proposed based on chemical stabilization. The mechanical behaviors of the stabilized soil, such as strength and stress-strain relationship, were investigated through a series of triaxial compression tests conducted at -1.0℃, and the mechanism of strength variations of the stabilized soil was also explained based on scanning electron microscope test. The investigations indicated that the strength of stabilized soil to resist failure has been improved, and the linear Mohr-Coulomb criteria can accurately reflect the shear strength of stabilized soil under various applied confining pressure. The increase in both curing age and cement mixing ratio were favorable to the growth of cohesion and internal friction angle. More importantly, the strength improvement mechanism of the stabilized soil is attributed to the formation of structural skeleton and the generation of cementitious hydration products within itself. Therefore, the investigations conducted in this study provide valuable references for chemical stabilization of warm and ice-rich frozen ground, thereby providing a basis for in-situ ground improvement for reinforcing warm and ice-rich permafrost foundations by soil-cement column installation.
基金This study was supported by MatSoil Company(Grant No.04G/2022)This research was funded by the European Union’s Horizon 2020 research and innovation program under the Marie Sklodowska-Curie(Grant No.778120).
文摘In recent years,there has been growing interest in developing methods for mitigating greenhouse effect,as greenhouse gas emissions continue to contribute to global temperature rise.On the other hand,investigating geopolymers as environmentally friendly binders to mitigate the greenhouse effect using soil stabilization has been widely conducted.However,the effect of CO_(2)exposure on the mechanical properties of geopolymer-stabilized soils is rarely reported.In this context,the effect of CO_(2)exposure on the mechanical and microstructural features of sandy soil stabilized with volcanic ash-based geopolymer was investigated.Several factors were concerned,for example the binder content,relative density,CO_(2)pressure,curing condition,curing time,and carbonate content.The results showed that the compressive strength of the stabilized sandy soil specimens with 20%volcanic ash increased from 3 MPa to 11 MPa.It was also observed that 100 kPa CO_(2)pressure was the optimal pressure for strength development among the other pressures.The mechanical strength showed a direct relationship with binder content and carbonate content.Additionally,in the ambient curing(AC)condition,the mechanical strength and carbonate content increased with the curing time.However,the required water for carbonation evaporated after 7 d of oven curing(OC)condition and as a result,the 14-d cured samples showed lower mechanical strength and carbonate content in comparison with 7-d cured samples.Moreover,the rate of strength development was higher in OC cured samples than AC cured samples until 7 d due to higher geopolymerization and carbonation rate.
基金financial support for the research provided by the National Natural Science Foundation of China(No.42107350)the National Key Research,Development Program of China(No.2023YFD1902801)the Central Government Guides the Development of Local Science and Technology Project,Grant/Award Number:Guike ZY21195022。
文摘A comprehensive understanding of aggregate dynamics is the foundation for establishing sustainable sugarcane production systems,especially in vulnerable red soil ecosystems.While existing studies have established a basic understanding of aggregate formation and stabilization,the functional relationship between aggregate stability and erosion resistance under extended sugarcane monoculture remains inadequately characterized.We employed an integrated methodology combining dry/wet sieving,the Le Bissonnais method and scanning electron microscopy to quantitatively evaluate the soil aggregate stability and erosion resistance across six distinct cultivation chrono-sequences(3–32 years)and two soil depths(0–15 cm and 15–30 cm)in the sugarcane cultivation area of Qingshui Village,Wuxuan County,Guangxi Zhuang Autonomous Region,China,aiming at providing insights for developing soil conservation strategies in sugarcane cultivation systems.The results reveal three core findings.First,planting years significantly influence the proportions of soil aggregates with varying particle sizes.Under the treatments with Le Bissonais methods,the mean weight diameter(MWD)under fast wetting,disturbance after pre-wetting,and slow wetting decrease with increasing planting years,while the relative dissipation index,relative mechanical fragmentation index,and erodibility factor(K)exhibit varying degrees of change,indicating progressive soil structural degradation and increased erosion susceptibility.Second,long-term sugarcane monocropping leads to declining soil organic carbon,liquid limit,plastic limit,and clay content,likely due to factors such as soil-forming materials and rainfall.Concurrently,the increased sand content and porosity weaken interparticle bonding and reducing aggregate stability over time.Third,correlation analysis demonstrates that MWD and geometric mean diameter(GMD)under disturbance after pre-wetting and slow wetting treatments show strong positive correlations with soil organic carbon,p H,clay content,liquid limit,and plastic limit but negative correlations with sand content,total porosity,and capillary porosity.Furthermore,K is significantly negatively correlated with soil physicochemical properties as well as GMD and MWD.These results help us understand the mechanism of aggregate stability variation in sugarcane-cultivated red soils and support the development of soil conservation strategies for sustaining sugarcane productivity in subtropical regions.
基金supported by the Polish National Science Center(Grant No.2022/06/X/ST10/00320)received by Witold Tisler.
文摘The present study investigates the engineering properties of submerged organic silt(orSi)stabilized with F-class fly ash(FA),with and without the addition of an activator(CaO).The utilization of F-class FA for soil improvement is an important aspect of sustainable and environmentally-conscious geotechnical engineering when marginal usage of lime and concrete is of great interest to engineers and societies.Currently,discussion is predominantly focused on the positive aspects of using the F-class FA,with a paucity of emphasis on the negative aspects.To explore these features more thoroughly,a series of strength and compressibility tests was conducted.The sample preparation and curing methodology were chosen to replicate the in situ conditions where soil is surcharged and submerged in water.It was found that the incorporation of F-class FA without an activator reduces the undrained shear strength of submerged orSi by about 20%–25%and permanently prevents any thixotropic strength restoration.An increase in undrained shear strength is observed when lime(3%–6%)is added to the soil–FA mixture or when only lime(in the same amount of 3%–6%)is used.Consequently,F-class FA can be successfully used as a filler for slurries with minimum lime content in soil mixing methods.The F-class FA(with or without an activator)shifts the so-called“creep delay”in time,consequently reducing the total creep settlements.The shift of“creep delay”is more considerable for orSi stabilized with lime or with FA and lime as an activator,than for orSi stabilized with pure F-class FA.
基金supported by the National Natural Science Foundation of China(NO.32201626)the Key Research and Development Program of Jiangxi Province(20223BBG74S01,20223BBG71013).
文摘In response to the effectiveness of reforestation in controlling soil erosion,there has been a dramatic increase in forest coverage in the hilly red soil region of southern China.Aggregate stability and soil shear strength are indicators that reflect soil resistance to erosion and its ability to prevent shallow landslides,respectively.However,limited research has focused on the response of soil aggregate stability and shear strength to reforestation.We selected three types of reforestations(Phyllostachys edulis forest,Cunninghamia lanceolata(Lamb.)Hook.forest,Citrus sinensis(L.)Osbeck.orchard),a natural forest(mixed coniferous and broadleaf forests),and a fallow land as study plots,and measured root traits,and soil physicochemical traits,i.e.,pH,soil organic matter(SOC),Soil water content(SWC),soil bulk density(BD),soil cohesion(c),soil internal friction angle(φ)and analyzed their multiple interactions.The soil aggregate stability traits,refer to the mean weight diameter(MWD)and geometric mean diameter(GMD),exhibited a significant increase in reforested plots,approximately 200%compared to fallow land and 50%compared to natural forests.For soil shear strength the values were approximately 20%higher than in fallow land and approximately 10%lower than in natural forests.Soil aggregate stability and soil shear strength did not exhibit a significant positive correlation across all plots,and the underlying drivers of these traits were variable.For instance,in natural forest and timber stands,soil aggregate stability was mainly influenced by soil organic carbon,while soil shear strength was primarily affected by root length density.In economic forest,aggregate stability and shear strength are mainly affected by organic carbon.Overall,we found that vegetation restoration enhances soil erosion resistance,however,the primary drivers for the improvement of aggregate stability(soil organic carbon)and shear strength(root length density)are different.Therefore,in future benefit assessments of vegetation restoration projects aimed at soil erosion control,different indicators should be considered based on specific conditions.
基金Funded by the National Key R&D Program of China (No. 2022YFC3803405)the China State Construction Key Laboratory Project (No. ZJXJ-PT-2022-14)。
文摘This study investigates the use of a low-carbon soil stabilizer called SDG,which is made up of granulated blast furnace slag (GGBFS),desulfurization gypsum (DG),and calcium carbide slag (CCS),to solidify the soil.The impact of SDG components on the strength and durability of solidified soil was analysed through a series of tests,including unconfined compressive strength,water stability coefficient,water absorption rate,drying-wetting cycles,and shrinkage tests.Furthermore,microstructure characteristics were analysed using X-ray diffraction (XRD) and scanning electron microscopy (SEM).The study shows that the solidified soil has excellent strength and durability when the SDG stabilizer contains 60% GGBGS,10% DG,and 30% CCS.Additionally,increasing the DG content negatively affects the soil's resistance to water.The SDG stabilizer has potential chemical cementitious characteristics and the calcium carbide slag is rich in calcium ions,which undergo an ion exchange reaction with minerals in the soil.These findings offer new ideas for the development of soil stabilizers.
文摘We read with great interest the investigations conducted by Pourakbar et al.(2024)on the“Stabilization of clay soil using alkali-activated sewage sludge.”The authors have investigated the feasibility of utilizing alkali-activated sewage sludge(AASS)as a binder for stabilizing the clayey soil.Sewage sludge(SS)in varying proportions of 1.5%,2%,2.5%,3.5%,and 4.5%was utilized to prepare geopolymer binders using sodium and potassium-based alkali activators.Furthermore,unconfined compressive strength(UCS)and direct shear tests were conducted to examine the strength development of clayey soil stabilized with AASS.While the study presented some intriguing results,we have identified critical concerns regarding(i)the selection of SS as a precursor for alkali activation,(ii)technical inconsistencies associated with the compaction characteristics and microstructural analysis,and(iii)the feasibility of the proposed methodology for practical applications.Through our discussion,we seek to highlight these issues and provide constructive feedback to advance the understanding of alkali activation processes and their implications for soil stabilization.
基金supported by the National Natural Science Foundation of China (41977020)the China Agriculture Research System of MOF and MARA (CARS22)。
文摘oil aggregates profoundly impact soil sustainability and crop productivity, and they are influenced by complexinteractions between minerals and organics. This study aimed to elucidate the alterations in mineralogy and soilorganic carbon(SOC) following long-term green manure incorporation and the effect on soil aggregates. Based on 5-and 36-year field experiments, surface soil samples(0–20 cm) were collected from Alfisol and Ferrisol soilssubjected to rice–rice–winter fallow(CK) and rice–rice–Chinese milk vetch(MV) treatments to investigate aggregatestability, mineralogy, SOC composition, and soil microstructural characteristics. The results showed that high clay-content Ferrisol exhibited greater aggregate stability than low clay-content Alfisol. The phyllosilicates in Alfisolprimarily comprised illite and vermiculite, whereas those in Ferrisol with high-content free-form Fe oxides(Fed) weredominated by kaolinite. Additionally, the clay fraction in Ferrisol contained more aromatic-C than the clay fraction inAlfisol. The 36-year MV incorporation significantly increased the Ferrisol macroaggregate stability(9.57–13.37%),and it also facilitated the transformation of vermiculite into kaolinite and significantly increased the clay, Fed, and aromatic-C contents in Ferrisol. Backscattered electron(BSE)-scanning electron microscopy/energy dispersive X-ray spectroscopy(SEM/EDS) revealed a compact aggregate structure in Ferrisol with co-localization of Feoxides and kaolinite. Moreover, the partial least path model(PLS-PM) revealed that clay content directly improvedmacroaggregate stability, and that kaolinite and Fed positively and directly affected clay or indirectly modulated clay formation by increasing the aromatic-C levels. Overall, long-term MV incorporation promotes clay aggregation by affecting mineral transformation to produce more kaolinite and Fe oxides and retain aromatic-C, and it ultimately improves aggregate stability.
基金supported by the Fundamental Research Funds for the Central Universities(Nos.202061027,202261063)the National Natural Science Foundation of China(No.41572247)。
文摘The traditional cement-based stabilization cannot effectively stabilize the marine soft clay under submerged conditions.In order to solve this problem,the enhancement of cement-stabilized marine soft clay was investigated in this study by adding the ionic soil stabilizer(ISS)and polyacrylamide(PAM).For this purpose,varying contents of ISS and PAM(ISS-P)were added into cement-stabilized marine soft clay and subjected to curing under submerged conditions.Atterberg limits tests,direct shear tests,unconfined compression strength(UCS)tests,water-stability tests,scanning electron microscopy analysis,and X-ray diffraction analysis were carried out.The results show that using 1.8%ISS and 0.9%PAM as the optimal ratio,the cohesion,internal friction angle,UCS,and water-stability of the samples increased by 182.7%,15.4%,176.5%,and 368.5% compared to the cement-stabilized soft clay after 28 d.The increment in soil cohesion with increasing ISS-P content was more apparent than that in the internal friction angle.The combined action of ion exchange attraction and electrostatic adsorption altered the failure characteristics of the samples,resulting in localized micro-cracking and multiple failure paths.Increasing the content of ISS-P strengthened the skeletal structure of soil,reduced inter-particle spacing,and enhanced the water-stability.Additionally,ISS promotes the hydration of cement and compensates for the inhibitory effect of PAM on early cement hydration.ISS-P can effectively enhance the strength and stability of submerged cement-based stabilized marine soft clay.
