Stabilization Of Soft Clay Research Articles

Feasibility of biochar for low-emission soft clay stabilization using CO2 curing

Use of traditional lime-cement binders on stabilizing soft sensitive clays pose a significant challenge for the construction sector to reach Finland’s carbon neutrality goals by 2030. Traditional stabilization recipes consisting of cement as binders contributing significantly to CO2 emissions (≅ 500 kg CO2 eq./ton in deep mixing alone). This laboratory study explores the feasibility of achieving near carbon-negative stabilization of soft clay leveraging accelerated CO2 curing (ACC) in biochar (BC) enhanced cementitious composites. BC, a by-product of the biofuel industry, is used as partial replacement of cement (0 %, 10 %, and 50 % of binder) in developing precast cementitious piles. One non-carbonated treatment and two ACC treatments are employed to assess their uniaxial compressive strength, thermogravimetric properties and CO2 sequestration capacity. The results demonstrate that synergistic effects of using BC with ACC not only enhances the compressive strength of the composites but also promotes CO2 uptake due to formation of stable carbonates. BC due to its surface functional groups, honeycomb porous structure, and hydrophilicity facilitated uniform CO2 diffusion in the clay matrix and likely improved internal curing. In ACC treated composites, the replacement of 50 % of cement with BC resulted in sufficient load-bearing capacity (≥50 kPa as per Finnish Guidelines) for both shallow and deep clay layers, making a suitable subgrade media for many types of geotechnical applications. The measured bound CO2 increased gravimetrically from 2 % to 41 % when cement was partially replaced by BC. In case of non-carbonated samples, 10 % partial replacement of BC provided high strength (≥200kPa). Life Cycle Assessment (LCA) of a case study of utilizing BC stabilized clay in deep mixing operations can potentially reduce net carbon emissions to −50 kg CO2 eq./ton.

Innovative Approaches to Soft Clay Stabilization: Utilizing Sustainable Materials for the Stone Column Technique

Innovative Approaches to Soft Clay Stabilization: Utilizing Sustainable Materials for the Stone Column Technique

Performance of incineration bottom ash amended marine soft clay stabilized by cement in seawater

Incineration serves as an effective waste management method driven by its ability to reduce mass and volume of municipal solid waste. However, this process generates incineration bottom ash (IBA), which is commonly disposed of in landfills in many countries, especially when dealing with fine IBA. To address this issue, recycling fine IBA for soft marine clay (MC) stabilization is a sustainable option compared to landfilling. Previous studies revealed that aggregate-like and weak hydration properties of fine IBA may increase the strength and decrease compressibility of MC. Nevertheless, when using IBA-MC in land reclamation or coastal protection, the performance may deteriorate, particularly in the presence of seawater. Therefore, this study employed chemical stabilization method combined with ordinary Portland cement (OPC), to solidify/stabilize IBA-MC (OPC-IBA-MC). The aim was to improve the performance of IBA-MC in seawater. The appearance, water content, strength, mineralogy, and microstructure of IBA-MC and OPC-IBA-MC soaked in seawater were investigated. The results showed that the strength of OPC-IBA-MC (4075 kPa) cured in air for three months was significantly higher than that of IBA-MC (983 kPa). Nevertheless, after soaking in seawater, OPC-IBA-MC was dismantled, rendering its strength untestable. The mineralogy and microstructure of OPC-IBA-MC revealed that the formation and growth of ettringite caused instability in OPC-IBA-MC in seawater.

Environmentally friendly binders from calcium carbide residue and silica fume and feasibility for soft clay stabilization

This investigation elucidates the development of an innovative, sustainable binder derived from calcium carbide residue and silica fume, aimed at enhancing soft clay stabilization with minimal environmental impact. Various mixtures were examined, focusing on the CaO to SiO2 molar ratio (Ca/Si), which varied from 1.85 to 0.65. Comprehensive analyses of the raw materials and pastes, including chemical composition, phase evolution, and microstructure, were conducted using techniques like Energy dispersive X-ray fluorescence, X-ray diffraction, thermogravimetric analysis, and scanning electron microscopy. Results indicate a significant impact of raw material fractions on the compressive strength and cementitious properties. The mixture with a Ca/Si of 1.55 demonstrated the highest long-term strength, attributed to increased C–S–H content. A mixture of 30 wt% calcium carbide residue and silica fume was found to improve the unconfined compressive strength of soft Bangkok clay by 84% compared to 10 wt% ordinary Portland cement, demonstrating its efficacy and potential for widespread application in green construction initiatives. This research not only promotes the recycling of industrial by-products, reducing environmental impact, but also represents a significant advancement in sustainable construction materials.

Stabilization of Soft Clay by a Low-Calcium Fly Ash Geopolymer

Stabilization of Soft Clay by a Low-Calcium Fly Ash Geopolymer

Stabilization of Soft Clay with Sustainable Binders for Dry Deep Mixing Design

Abstract Dry deep mixing (DDM) is a soil stabilization method widely used in countries with large soft clay areas, such as in the Nordic countries. In Finland, DDM is performed using a binder material that commonly consists of cement and lime in a 50:50 or 30:70 ratio. However, both lime and cement generate large amounts of emissions of carbon dioxide, which has led to a shift toward alternative materials in recent years. This paper presents the results of an extensive testing program where samples of Finnish sensitive soft clay are stabilized with eight different low emissions binders and tested by means of the uniaxial compression strength test. The alternative binders comprise different by-products and/or pozzolanas in varied percentages, which include lime kiln dust (LKD), biomass-based fly ash from bioenergy production, gypsum, blast furnace slag, as well as lime and cement in reduced amounts. The tests were performed on samples stabilized at different binder densities (60, 70, 100, 120, 140, and 160 kg/m3) and after 28 days of curing to determine the optimum densities for DDM design purposes. The results showed that binders such as blast furnace cement, the cement- quicklime-gypsum (33:33:33), and the LKD-cement (50:50) exhibited higher strength than the traditional lime/cement binders at different binder densities. In addition to these results, a simplified CO2 emissions calculation procedure is proposed for a DDM design supporting a road embankment, and two different emissions factors are obtained for the investigated binders. The results showed that some alternative binders can provide high binding efficiency with low CO2 emissions.

On the use of one-part geopolymer activated by solid sodium silicate in soft clay stabilization

The application of geopolymers in ground improvement has garnered significant attention in recent years. However, most geopolymer preparations have focused on the two-part method, which not only has negative environmental impacts but also falls short of meeting practical requirements. This study aimed to address these limitations by employing solid sodium silicate (Na2O·nSiO2, n is the molar ratio, NS) to activate binary precursors (fly ash [FA] and ground granulated blast furnace slag [GGBFS]), along with water, to synthesize a one-part geopolymer (OPG) for soft clay stabilization. The primary factors on the properties of the OPG binder were firstly identified through macro- and micro-tests. Subsequently, the optimization of the OPG mixing proportion was achieved by reducing the molar concentration of NS, and was further used for soft clay stabilization. The effects of the FA/GGBFS ratio (0, 0.1, and 0.2), curing period (7, 14, and 28 days), and binder content (0.15, 0.20, and 0.25) on the mechanical properties of the OPG-stabilized soft clay were then evaluated using unconfined compressive strength (UCS) tests. Furthermore, mercury intrusion porosimetry (MIP), scanning electron microscopy with energy dispersive X-ray spectrometry (SEM-EDS), and X-ray diffraction (XRD) techniques were employed to examine the evolution of microstructure, hydrate composition, and mineral/phase of the OPG-stabilized soft clay samples. The experimental results indicated that an appropriate OPG stabilizer proportion was achieved with an FA/GGBFS ratio of 0.1, water/precursor ratio of 0.8, molar ratio of NS of 1.0, and molar concentration of 3 mol/L. The high-early-strength feature of OPG binder contributed to the rapid strength development of the stabilized soft clay at an early age. A noticeable pozzolanic reaction was observed in the OPG-stabilized soft clay sample with an FA/GGBFS ratio of 0.1. Additionally, a binder content of 0.20 was recommended for the stabilization of soft clay due to its optimal balance between economic benefits and meeting the required UCS criteria in soil stabilization. Finally, a reliable nonlinear relationship between UCS and porosity of OPG-stabilized soft clay was established to assess the mechanical properties and stabilization effects of the OPG-stabilized soft clay for practical applications. This study greatly enhances the scientific understanding of geopolymerization in the OPG system by using a combination of the binary precursor of FA and GGBFS and the solid NS activator. It sheds light on the stabilization mechanism of OPG-stabilized soft clay. The outcomes of this study make a valuable contribution to the advancement of environmentally friendly soil stabilizers, promoting green and low-carbon practices in the field of ground improvement.

Performance of Treated Soft Clay with Nano-Modified Cementitious Binders at Reference and Cold Temperatures

Lime is considered the preferred choice for the treatment of the high plasticity clayey soils; however, for environmental concerns (quality of water and vegetation), it is prohibited in many regions, including Manitoba, Canada. Hence, it is imperative to find a suitable treatment alternative that provides an optimal solution for such a problematic soil type during different periods of the construction season. Hence, improvement of problematic/weak soils such as soft clay by nano-modified cementitious additives was tested under normal and cold conditions. This approach may significantly impact the construction of roads/pavements in cold regions. This current study focused on investigating the effects of single, binary, and ternary cementitious systems, comprising General Use cement (0–15%) with/without slag (0–15%), and nano-silica (0–3%), on the properties of soft clay (Type A7/CH) under reference (22 ± 2 °C) and cold temperatures (+ 5 °C). The mechanical performance of the control and treated mixtures were tested in terms of California Bearing Ratio (CBR) as well as unconfined compressive strength at 7, 28, 56, and 91 days of curing, while the durability properties were assessed based on the resistance to freezing–thawing cycles [durability factor (DFF/T)]. Moreover, thermogravimetry and scanning electron microscope analyses were conducted to corroborate the trends of the aforementioned tests. In comparison to the untreated clay, increasing the binders’ content significantly enhanced the mechanical/durability properties of the soil treated herein. The ternary mixtures comprising cement, slag and nano-silica showed the highest mechanical and durability properties at both reference and cold temperatures. Its CBR, 7-day compressive strength, 28-day compressive strength, and DFF/T were 46.3 and 31.6%, 700 and 562 kPa, 1349 and 891 kPa, and 94 and 71%, respectively. Such mixtures may present a viable option for soft clay stabilization at low temperatures, thus contributing to extending construction activities during fall and spring periods in cold regions.

Discussion of “Soft Clay Stabilization Using Three Industry Byproducts” by Bo Xu and Yaolin Yi

Discussion of “Soft Clay Stabilization Using Three Industry Byproducts” by Bo Xu and Yaolin Yi

Stabilization of Soft Clay from Bukit Rawi using Portland Composite Cement

One method for stabilizing soft clay is to mix it with cement. Portland composite cement (PCC) is a cement produced by grinding together portland slag and gypsum with one or more inorganic materials that is suitable for stabilization of soft soils. The purpose of this study was to mix soft clay from Bukit Rawi, Central Kalimantan with PCC, which was then tested for unconfined compression strength (UCS) and the California Bearing Ratio (CBR) to see if it could be used as a road subgrade. Soft soil from Bukit Rawi was mixed with PCC with percentages of 6%, 8%, 10%, and 12% on a dry weight basis. The mixture was tested by Proctor standard compaction to obtain the optimum moisture content and maximum dry density. At these optimum conditions, UCS and CBR tests were carried out. The findings reveal that adding PCC to Bukit Rawi soil enhances UCS and CBR, which were previously 3.47% of CBR and 0.67kg/cm2 of UCS. The addition of PCC with a level of 2‒3% is planned for field application, because it is considered capable of fulfilling the requirements as a subgrade layer with a CBR of 15%. Furthermore, 12 percent PCC is required in the combination as a foundation (minimum 20kg/cm2 of UCS).

Feasibility of lime and biopolymer treatment for soft clay improvement: a comparative and complementary approach

Highway pavement infrastructure projects which involve soil improvement should be executed, ensuring environmental sustainability. In the present study, guar gum (GG) and lime were assessed for the purpose of soft clay stabilization. The experimental program for the soil stabilization employed a two-stage process. The initial stage involves treatment of the soil with various percentages of lime (3, 5, 7, and 9%) and GG (0.6, 1.0, 1.4, and 1.8%), maintaining the same material acquisition cost and considering curing (0, 7, 14, and 28 days) for the unconfined compressive strength (UCS). In the second experimental stage, a complementary approach in which 3% lime was combined with GG at various percentages (0.1, 0.2, and 0.3%) was employed. The tests conducted include UCS, California bearing ratio (CBR), and strength loss resistance (SLR). Results show that the sole use of lime and GG resulted in significant improvement in the UCS, albeit lime was better. While UCS improved with curing time for the lime-stabilized soil, UCS gain for GG occurred only for up to 7 days curing because biodegradation of GG by microbes in the soil ensues on further curing. Lime-GG stabilization resulted in better UCS and CBR improvement with curing than lime stabilization; however, lime stabilization yielded better SLR. The optimum additive content for strength improvement was obtained at 3% lime + 0.3% GG. Microstructural analysis indicated cementation in the stabilized soil. Predictive models for the UCS were developed based on regression methods. Model evaluation revealed that Gaussian process model provided the best UCS prediction.

Stabilization of Soft Clay Using Perlite Geopolymer Activated by Sodium Hydroxide

Stabilization of Soft Clay Using Perlite Geopolymer Activated by Sodium Hydroxide

Settlement and Stress Analysis of Soil–Cement Column-Reinforced Foundation under an In Situ Stabilized Layer

Abstract Ground improvement using a joint technology combined with in situ shallow stabilization of soft clay and soil–cement column-reinforced foundations is an effective technique for the treatme...

THE EFFECT OF UTILIZING SILICA FUME AND EGGSHELL ASH ON THE GEOTECHNICAL PROPERTIES OF SOFT KAOLIN CLAY

The application of chemical stabilizer in soil stabilization can effectively reduce the negative environmental impact in the construction industry. However, the stabilization of soft clay remains a challenge due to the costly and non-eco-friendly materials such as cement and lime. This research demonstrates the combination of SF and ESA in stabilizing the kaolin soils, based on the basic engineering properties and undrained shear strength (USS). Its effect was studied via the inclusion as cement replacement material in kaolin soil at 2, 4 and 6% (by weight of dry soft kaolin clay soil) of SF and ESA substitutions of 3, 6 and 9% (by weight of dry soft kaolin clay and SF content). The result shows a considerably lower specific gravity (4.9% reduction), reduced plasticity index (PI)(48.4% reduction), decreased maximum dry density (MDD) (5.5% reduction), increased optimum moisture content (OMC)(8.7% increment), and higher USS (68.8%). In conclusion, the combinations of SF and ESA as soil stabilization agents successfully enhance the soil strength of the kaolin opening a route to the low cost and eco-friendly materials in soil stabilization.

A Generic Framework of Unifying Industrial By-products for Soil Stabilization

This paper presents a newly proposed generic framework for unifying different industrial by-products (IBPs) as composite binders to potentially replace ordinary Portland cement (OPC) for soft clay stabilization. The concepts of three chemical moduli (TCM) and strength activity index (SAI) are used to determine the fractions of different IBPs, and the final design mix is further tuned by adding gypsum for additional strength gain contributed by density due to ettringite formation. As a case study, a coastal soft clay was stabilized by different IBPs and gypsum using the new generic framework. Results show that the highest unconfined compression strengths of the IBPs stabilized clay cured for 7, 28, and 60 days reach 0.75, 1.21, and 1.39 MPa, respectively, which are even higher than those of the OPC-stabilized counterparts, suggesting the possibility of using IBPs to substitute OPC. Moreover, the additive gypsum plays a beneficial role for more strength gain due to the formation and volumetric expansion of ettringite. The implementation strategy for the new framework is recommended, and its practical implications for soil stabilization are discussed in terms of IBPs recycling and reuse, environmental sustainability, and economic benefits.

Influence of sand incorporation on unconfined compression strength of cement-based stabilized soft clay

Cement-based stabilization by deep mixing or grouting is a popular method used to enhance soft clay ground because clay gradation has a significant effect on its unconfined compression strength. However, the functional relationship between the gradation and the strength is currently unclear, which limits the assessment and cognition for the strength formation of cement-based stabilized soft clay. Strength experiments controlling the sand ratio were conducted, in addition to the literature review, to clarify the sand incorporation effect on the strength. An effective cement ratio (the mass ratio of cement to involved clay) was proposed to evaluate the strength of stabilized clay with sand incorporation. In order to combat data dispersion and the labour-intensive nature of these experiments, meso-mechanical numerical simulations were carried out by the finite element method. This served to enrich the data and clarify the mesoscopic mechanism. The numerical result indicates that the strength of stabilized clay at low sand incorporation ratio is mainly controlled by the strength of the cement-clay-water matrix, thus verifying the rationality of studying the effective cement ratio. Subsequently, the threshold sand ratio in the cement-clay-water matrix was discussed to optimize the stabilization of soft clay.

Soft Clay Stabilization Using Three Industry Byproducts

AbstractIn order to reduce the disposal of industrial byproducts and the environmental impacts associated with ordinary Portland cement (OPC) production, it is encouraged to use industrial byproduc...

SOIL STABILIZATION AND IMPROVEMENT OF MARINE CLAYS USING CEMENT AND LIME IN A MARSHLAND

This study assesses the stabilization of marine clay soil using cement and lime to improve on the subgrade material. The tests conducted include: the natural moisture content, specific gravity, sieve analysis, Atterberg limit, compaction and California Bearing Ratio (CBR). The types of stabilization used were mechanical and chemical. The results obtained were classified using AASHTO classification system and based on the results the soil corresponds to group A-6 soils. The highest CBR values of 33.24% and 424.35% were obtained at 20% cement content for unsoaked and soaked and for lime the highest CBR values were 5.07 and 10.46 for 11% lime content for both unsoaked and unsoaked. Based on the results obtained, the addition of cement and lime to clay soil in the presence of water improved the CBR values for soft clay stabilization for highway construction with low traffic volume. It is therefore concluded that the addition of cement and lime to clay soil improved the bearing capacity and the maximum dry density of the clay soil. Further research should be carried out to examine the effects of industrial by-products on effective clay soil stabilization.

Experimental investigation on the stabilization of soft clay using granulated blast furnace slag

Soft clay is associated with a soft consistency and poor shear strength. High percentage fines lead to higher liquid limit and lower plasticity index. Low bearing capacity and excessive settlement lead to uneconomic engineering structure constructed over it. There is a serious need to mitigate this problem and hence soil stabilization is the need of the hour. In the present study, Granulated Blast Furnace Slag (GBFS) which is an industrial waste/by-product of steel industry is used as a stabilizer to improve the geotechnical property of the soft clay. Soft clay is replaced by granulated blast furnace slag in various percentages by weight (10%, 20%, 30%, 40% and 50%) and examined for its plasticity, compaction and strength properties of the mix. From the experimental investigation, it is shown that the plasticity index decreases and unconfined compressive strength (UCS) increases upon addition of slag to the soil. With the curing age, UCS value increased indicating the chemical reaction between free lime and soil. 40% slag replacing the soft clay is recommended as stabilizer as it gave the maximum increase in UCS value compared to the rest mix. Based on the laboratory work, it can be concluded that granulated blast furnace slag can be used as a potential stabilizer for soft clay and also largely solves the problem of disposal of slag.

Soft clay stabilization using ladle slag-ground granulated blastfurnace slag blend

Ladle furnace basic slag (ladle slag, LS) is a by-product of the steel refining process. There is a great amount of LS generated worldwide every year and the current solution is simply landfilling it, which causes both economic and environmental issues. This study attempts to use LS to activate ground granulated blastfurnace slag (GGBS) for stabilization of soft clay, as well as immobilization of heavy metals in LS. The LS-GGBS-stabilized clays with different binder contents and LS:GGBS ratios were cured for different periods, and then subjected to unconfined compressive strength (UCS) test, leaching test, and X-ray diffraction (XRD). The results indicated that the LS-GGBS-stabilized clays with LS:GGBS ratio of 2:8–5:5 could achieve similar or higher UCS compared to ordinary Portland cement-stabilized clay after 56 days of curing. The leaching of potential heavy metals was not detected for the LS-GGBS stabilized clays. According to XRD analysis, the main hydration products of LS-GGBS-stabilized clay were calcium silicate hydrates (CSH) and ettringite, which were responsible for the strength development of LS-GGBS-stabilized clays.