Unconfined Compressive Strength Values Research Articles

Reusing COVID-19 personal protective equipment wastes for pavement base, subbase, and subgrade applications

Since 2019, the coronavirus disease (COVID-19) pandemic has caused a substantial increase in personal protective equipment waste generation, resulting in significant environmental concerns. In addition, the expansive clay subgrade (ECS) must be stabilized prior to pavement construction because of its unfavorable engineering properties. The use of recycled concrete aggregates (RCA) in pavement bases/subbases offers a sustainable solution to decrease the demand for quarry materials and waste pile-up. However, RCA should be reinforced for base and subbase applications because of its low shear and dynamic properties. This study explores an innovative waste solution by recycling shredded nitrile gloves (SNG) to stabilize clay subgrades and reusing discarded shredded face masks (SFM) to treat RCA for base/subbase applications. A series of experiments including compaction, unconfined compression strength, and repeated-load triaxial tests were conducted. The test results showed that the incorporation of SNG and SFM improved the strength and stiffness of the pavement layers. The addition of 1.5% SNG to ECS resulted in the highest unconfined compressive strength (UCS) value (315.50 kPa) and highest resilient modulus (Mr) (79.98 MPa). Furthermore, introducing 1% SFM into RCA increased the UCS and Mr to peak values of 216 kPa and 314.35 MPa, respectively.

Performance of Nickel Slag as a Stabilization Material for Soft Soil

The chemical soil stabilization method is an effort to improve soil bearing capacity according to soil work specifications in construction. The use of conventional stabilization materials, such as cement and lime, is considered environmentally unfriendly. Utilizing by-products from the mining industry becomes an alternative that can be developed in soil improvement efforts. This research aims to examine the influence of nickel slag on the enhancement of soil bearing capacity as observed through its unconfined compressive strength value. In this study, the concentration of added nickel slag as a stabilization material is 3%, 6%, 9%, and 12% by dry soil weight. The test specimens used are cylinders with a diameter of 5 cm and a height of 10 cm. Unconfined compressive strength testing is conducted after the specimens are cured for 14 days. The results of this study indicate that the clay soil used is classified as organic clay with high plasticity based on the USCS classification, with an unconfined compressive strength value of 0.2 kg/cm2. The addition of nickel slag with concentrations of 3%, 6%, 9%, and 12% results in respective increases in unconfined compressive strength by 46%, 50%, 68%, and 47%. These findings demonstrate that the optimum nickel slag content of 6% provides the maximum unconfined compressive strength. Therefore, it can be concluded that nickel slag, as a source of silica, has the potential to be used as an alternative material in soft soil improvement.

Optimization of physical and strength performance of cellulose-based fiber additives stabilized expansive soil

Expansive soils are known as geotechnically problematic soils and represent a significant challenge for both civil engineering and geotechnical applications. The primary issue with expansive soils is their susceptibility to moisture-induced volume changes, resulting in both shrinkage and swelling behaviors. This study presents a comprehensive investigation into optimizing the physical and strength properties of expansive soil through the use of cellulose-based fiber additives, namely bamboo fiber (BF), rice husk fiber (RHF), and wheat straw fiber (WSF). Various fiber dosages (5 %, 10 %, and 15 %) and sizes (75 µm, 150 µm, and 300 µm) were employed in combinations to identify the optimal conditions and analyze the soil-fiber reinforcement mechanisms. The experimental design was leveraged by the Taguchi method to optimize conditions, focusing on key response factors such as the Atterberg limit test (PI, LL), free swell ratio (FSR), linear shrinkage (LS), and unconfined compressive strength (UCS) and statistical analysis for results were validated by Analysis of Variance (ANOVA). Additionally, cellulose content and water absorption capacity were assessed to confirm the suitability of cellulose-based fibers as soil stabilizers. Hence, the results demonstrate a substantial enhancement in both the physical and mechanical properties of the stabilized soil with the incorporation of cellulose-based fiber additives. Specifically, the Plastic Index (PI) improved by 85 % when using RHF fibers at a dosage and size of 15 % and 300 µm, respectively. The Free Swell Ratio (FSR) witnessed improvement with WSF fibers at a dosage of 15 % and a size of 150 µm. Linear shrinkage exhibited remarkable improvement, exceeding 95 %, with a combination of 15 % and 75 µm fibers. Furthermore, the Unconfined Compressive Strength (UCS) values were improved by more than 100 % when using 15 % BF fibers with a size of 300 µm. Therefore, the findings of the study highlight that cellulose-based additives as highly effective and sustainable alternatives for soil stabilization, surpassing the engineering performance of traditional soil stabilizers

Review of Correlations between Unconfined Compressive Strength (UCS) Values and Dynamic Cone Penetrometer (DCP–DN) Values of Stabilized Soils

Review of Correlations between Unconfined Compressive Strength (UCS) Values and Dynamic Cone Penetrometer (DCP–DN) Values of Stabilized Soils

Experimental Study on the Road Performance of Phosphogypsum-Modified Lime-Fly Ash Stabilized Red Clay

To assess the impact of solid waste phosphogypsum on the road performance of lime-fly ash-stabilized red clay, we conducted comprehensive tests on the road performance, swelling and shrinkage characteristics, and mechanical properties of lime-fly ash soil with varying phosphogypsum content and curing age. Additionally, we analyzed the microstructure and composition changes using scanning electron microscopy and X-ray diffraction tests. The results revealed that phosphogypsum significantly enhances the early strength and moisture stability of lime-fly ash soil. The mechanical properties of lime-fly ash soil continue to improve with increased curing age, with performance improvements tapering off after 60 days and eventually stabilizing. Moreover, as the phosphogypsum content increases, the unconfined compressive strength (UCS), splitting strength, and CBR value of the lime-fly ash soil initially increase and then decrease. The optimal mixing ratio was determined to be 4% phosphogypsum, resulting in a 7-day UCS increase of 67.2%, a 28-day UCS increase of 3 times, and a 28-day splitting strength increase of 4.3 times. The moisture stability coefficient also exhibited a 43% increase after 7 days, and its anti-disintegration ability was enhanced, reaching 0.91 after 28 days, which meets the specified standards. Microscopic analysis revealed that the addition of phosphogypsum improved the overall integrity of the lime-fly ash soil, and the formation of ettringite effectively filled the soil’s pores. However, excessive ettringite caused increased expansion and deformation. To optimize the use of phosphogypsum-modified lime-fly ash-stabilized red clay as subgrade filler, it is advisable to incorporate additives to further reduce swelling deformation.

Effects of metakaolin and sodium silicate treatment on highwater content dredged clay for improved construction fill performance

This study experimentally investigated the strength characteristics of metakaolin (MK) and sodium silicate (SS) treated dredged clay at high water content for use as construction fills. A series of laboratory tests including direct shear tests, unconfined compression tests, SEM and XRD tests were carried out to systematically evaluate the effects of water content, sodium silicate modulus, curing agent content, and curing time on the strength behavior of MK and SS treated dredged clay samples. The direct shear test results showed that the shear strength at a given vertical stress consistently increases with the increase of curing agent content and curing time while decreasing with the modulus of SS. Both cohesion and friction angle increase with increasing curing agent content and curing time, while reducing with the increasing modulus of SS. Unconfined compression test results showed that all samples tested exhibit a strain-softening behavior. The value of unconfined compressive strength increases with the increase of curing agent content and curing time but decreases with the increase of water content and modulus of SS. The optimal dosage combination is a sodium silicate modulus of 0.9, curing agent content of 12%, and curing time of 28d. SEM test confirmed the formation of gels in the treated soil sample, the dredged clay showed a more uniform and denser microstructure after treatment. Through XRD analysis, it is not easy to generate direct chemical reactions with no new mineral components generated in the sample. For high-water content dredged clay, it is recommended to use an optimum dosage combination of MK and SS to achieve a better treatment effect for use as construction fills.

Influence of Eggshell Ash and Stone Powder on Geotechnical Properties of Expansive Clay in Dukem Town

Expansive clays exhibit a distinctive swelling–shrinkage behavior, leading to structural distress and damage when subjected to varying moisture levels during different seasons. So, to mitigate these issues, stabilization techniques are commonly employed, aiming to diminish swelling tendencies and enhance the strength characteristics of expansive clays. This study delves into the transformative impact of utilizing eggshell ash (ESA) and stone powder (SP) as stabilizing agents on both the index properties and strength parameters of expansive clays. The selection of these stabilizing agents is guided by criteria encompassing cost-effectiveness, availability, and environmental compatibility. Through comprehensive analysis utilizing scanning electron microscopy (SEM) and X-ray diffraction (XRD), the mineralogical compositions of both soil and additives are meticulously examined. The XRD analysis of the expansive clay unveils the presence of minerals such as quartz, sanidine (potassium or sodium feldspar), and magnetite. Incorporating ESA into the expansive clay matrix yields substantial improvements across various soil index values, encompassing the free swell index, free swell ratio, linear shrinkage, and unconfined compressive strength value. To further amplify these benefits, the study extends its focus to the influence of SP while maintaining a consistent 6% ESA content. Notably, the addition of SP exhibits a significant enhancement in compressive strength, alongside other crucial properties. Synthesizing these findings, the laboratory results point to an optimal combination ratio of 6% ESA and 15% SP, as a recommended approach to achieve superior stabilization effects. This research contributes to a deeper understanding of the interplay between stabilizing agents and expansive clays, paving the way for improved engineering practices and more resilient structural designs.

Assessing the effect of lime-zeolite on geotechnical properties and microstructure of reconstituted clay used as a subgrade soil

This study investigates the replacement of conventional stabilizers with eco-friendly alternatives, with a specific focus on enhancing pavement subgrade applications. This research aims to evaluate the impact of lime-zeolite treatment on the properties of clayey subgrades and its potential to outperform traditional stabilization methods. Various tests, such as Proctor compaction, Atterberg limits, swelling, and unconfined compressive strength (UCS), were performed considering the plasticity index variation. Optimal zeolite replacement led to significant improvements in the clayey soils' behavior. It reduced the plasticity index by up to 9.4% and almost eliminated swelling. Furthermore, unconfined compressive strength (UCS) values were enhanced by up to 7.56 times when compared to untreated soil. Ultrasonic pulse velocity (UPV) tests indicated substantial increases in primary wave velocity (Vp) and constrained modulus (Mv), reaching values of 2650 m/s and 9600 MPa, respectively, representing improvements of around 6.5 times and 50 times over untreated clay. The results highlight the remarkable efficacy of lime-zeolite substitution, particularly at a 25% replacement level. The improvements in plasticity, swelling, and strength characteristics signify the potential of this eco-friendly approach in pavement subgrade enhancement. The significant increases in UPV parameters provide insights into the improved structural integrity of the treated soils. This innovative approach offers valuable contributions to pavement subgrade design by addressing plasticity, swelling, and strength issues in clayey soils, ultimately leading to more sustainable and effective infrastructure projects.

Stabilization of Batu Pahat Peat by Using Rice Husk Ash (RHA)

Malaysia possesses the distinction of being the ninth biggest expanse of peat soil land globally, hence encountering significant geotechnical challenges characterised by elevated moisture content, substantial organic composition, diminished shear strength, and reduced bearing capacity. The objective of this study is to investigate the fundamental geotechnical characteristics and strength of Batu Pahat peat that has been stabilised using Ordinary Portland Cement (OPC) and Rice Husk Ash (RHA). The application of Ordinary Portland Cement (OPC) in the process of peat stabilisation has the potential to enhance the mechanical properties and strength of the soil. Nevertheless, the extensive utilisation of cement might result in environmental degradation. Therefore, it is imperative to consider the incorporation of agricultural waste by-products as a partial substitute for cement. Hence, the objective of this research is to employ Rice Husk Ash (RHA) as a supplementary material in cementitious systems. An experimental investigation was undertaken to determine the ideal mix ratio by replacing cement with rice husk ash (RHA) in the range of 5% to 20%. The findings indicate that the peat under investigation can be classified as a hemic peat variety characterised by a high level of acidity. The experimental findings indicated that the peat treated with a 5% concentration of rice husk ash (RHA) (referred to as C95 RHA5) exhibited the maximum Unconfined Compressive Strength (UCS) value of 262 kN/m2. To validate the findings of the Unconfined Compressive Strength (UCS) test, an additional analysis was performed using the Scanning Electron Microscope-Energy Dispersive X-Ray (SEM-EDX) technique. This examination aimed to confirm the presence of calcium, which serves as evidence for the observed improvement in strength. In conclusion, it can be inferred that the utilisation of RHA as a substitute for cement at a proportion of 5% exhibits potential for application in Hemic peat.

Pengaruh Waktu Pemeraman Terhadap Nilai Kuat Tekan Bebas Dan Permeabilitas Tanah Lempung Yang Dicampur Dengan Semen Dan Abu Ampas Tebu

Soft clay has a relatively low subgrade bearing capacity and relatively large subgrade compression and lasts for a relatively long time so that it becomes a major problem in the development of transportation infrastructure. One of the efforts to improve soft clay soil is by adding bagasse ash and cement as a stabilizing agent on the soil. The research aims to determine the curing time on the value of unconfined compressive strength in clay soil after adding bagasse ash and cement, the permeability value of clay soil after adding bagasse ash and cement and the comparison value of unconfined compressive strength with curing time. This study used a variation of 0%,5%,10%,15% of palm bunch ash and cement by 5% of the dry weight of the soil. The test results of the free compressive strength value with a curing time of 0 days at 5% Cement + Sugar Bagasse Ash 0%, 5%, 10%, and 15% there was an increase and decrease in the value of the free compressive strength (Qu), in this case the highest Qu was in the variation cement 5% and bagasse ash 10% with a curing time of 14 days an increase in cohesion value of 0.716. The permeability coefficient increases with the increase in the percentage of bagasse ash with a fixed percentage of cement. With an average increase in the coefficient of permeability of 0.0149.

The effect of thermal stabilization process on mineralogy, morphology and engineering properties of red soil in southern Iran

Red soil from southern Iran is widely utilized in structural foundations, road construction, brick making, and high-level landfills. When subjected to heat, soils undergo significant changes in their physical, mechanical, and microstructural characteristics. This study aims to investigate the impact of temperature on the engineering properties of red soil, with a focus on the microstructural perspective. To achieve this, we conducted a series of macrostructural tests (unconfined compressive strength, gradation, weight loss, and permeability) and microstructural analyses (pH, electrical conductivity, X-ray diffraction (XRD), Energy-dispersive X-ray spectroscopy (EDX), and scanning electron microscopy (SEM)) on Iran red soil samples. The samples were subjected to temperatures ranging from 100 ℃ to 900 ℃ for 2 h. The key findings of this research highlight significant changes in the engineering properties of red soil, particularly at temperatures between 500 ℃ and 900 ℃. Microstructural observations revealed various alterations, including dehydration, dehydroxylation, changes in soil texture, formation of cavities, and increased porosity within the soil structure. Notably, at high temperatures (approximately 900 ℃), new crystalline minerals such as Gehlenite, Diopside, Anorthite, Sanidine, and Mullite were formed. The unconfined compressive strength values exhibited a remarkable increase, reaching nearly 20 times, from 0.12 MPa to 2.3 MPa, concurrently with the formation of new compounds, including the α -β quartz transition. Overall, this study sheds light on the profound effects of temperature on the engineering properties of red soil in southern Iran, offering crucial insights for its practical applications in construction and related fields.

Compressive and Tensile Strength of Nano-clay Stabilised Soil Subjected to Repeated Freeze–Thaw Cycles

Abstract Improvement of the mechanical properties of clayey soils by additional elements to enhance the strength under numerous freezing and thawing cycles has been considered as a serious concern for engineering applications in cold regions. The objective of the current study is to investigate the effect of nano-clay as a stabiliser on the mechanical properties of clay. To this end, the clay specimens were prepared by adding various percentages of nano-clay ranging from 0.5% to 3% by dry weight of soil and were experimentally tested under the uniaxial compression and tensile splitting tests under different curing times (0, 7 and 28 days) after experiencing various freeze–thaw cycles ranging from 0 to 11. It can be concluded from the results that nano-clay particles may be used as a stabiliser in geotechnical applications to improve soil property. The results indicate that the optimum moisture content (OMC) of specimens increases and the maximum dry density (MDD) decreases with the increasing nano-clay content. The specimens containing about 1% nano-clay recorded maximum values of unconfined compressive strength (UCS) as well as tensile strength. For example, the addition 1% nano-clay increased the UCS and tensile values of clay specimens under the curing time of 28 days by 34% and 247%, respectively. In addition, the long-term durability of specimens against freeze–thaw cycles increases further with the addition of nano-clay content ranging from 2% to 3%.

The Effect of Existing Soil on the Unconfined Compressive Strength (UCS) Value on Cement Treated Recycling Base (CTRB) Type Flexible Pavement

Recycling technology or Cement Treated Recycling Base (CTRB) is one method for repairing damage to ancient road pavements, however, when the process is in place (Mixed in place), difficulties can arise, such as mixing with existing soil material that shouldn't be mixed in its implementation. because this will affect the results of Unconfined Compressive Strength (UCS). As a binder in the form of local cement from South Kalimantan, the brand is cheaper because production costs are cheaper. This study aims to obtain UCS Results at minimal cement levels that still meet the requirements with the use of brand local cement, obtain the typical influence of existing soil on UCS and what percentage of existing soil material can still be tolerated either curing or non-curing and correlation and get recommendations for the maximum percentage of influence of percent of existing land on UCS in curing or non-curing conditions. RAM samples were obtained for the purpose of investigation, which was done in a lab, existing soil and additional materials in the field. Inspection of old aggregates, making test specimens with variations in cement content of 1-10%, after obtaining minimum UCS according to technical requirements then making test specimens with variations in soil examinations and soil content of 0%, 5%, 10%, 15%, 20%, and 25% again then conducting data analysis to find correlations / relationships. The results of the research showed variances in cement content of 1% (one) - 10% that still meet the technical specifications of UCS (at least 30 kg/cm²) obtained a minimum cement content of 5% (five percent) with a UCS of 33.77 kg/cm². Then the test results of the influence of existing soil on UCS that is still tolerated are mixed, namely in curing conditions is 17% with the equation Y = -0.10075 x + 46.894 (R2 = 0.964). and non-curing 8.9% with the equation Y = -0.1113 x + 39.814 (R2=0.956). The R2 conclusions for both indicate a very There is a substantial correlation between the two factors

Utilization of Plastic Waste as Soil Stabilization Material and Their Effect on Unconfined Compressive Strength Values

Utilization of Plastic Waste as Soil Stabilization Material and Their Effect on Unconfined Compressive Strength Values

Stabilization of Soil Using Concrete Slush Waste and Polyester Fibres

Abstract: Soil stabilization is a technique used in civil engineering to enhance the engineering properties of soil so that it can withstand large loads without shear failure. Many chemicals, by products and waste materials can be utilized for stabilization. In the present work, the behavior of soil after addition of the Concrete Slush Waste (varying proportion 4%, 8% and 12%) and Polyester Fibre (varying proportion 0.5%, 0.75%, and 1.0%; length 40 mm) was studied at different proportion and then various soil properties like Optimum Moisture Content, Maximum Dry Density, California Bearing Ratio, and Unconfined Compressive Strength values were determined. To conclude the current experimental research, it was ascertained that a combination of Concrete Slush Waste and Polyester Fibre can be used to improve the various engineering properties of soil.

Study on Preparation and Performance of Foamed Lightweight Soil Grouting Material for Goaf Treatment.

The harm goafs and other underground cavities cause to roads, which could lead to secondary geological hazards, has attracted increased attention. This study focuses on developing and evaluating the effectiveness of foamed lightweight soil grouting material for goaf treatment. The study examines the foam stability of different foaming agent dilution ratios by analyzing foam density, foaming ratio, settlement distance, and bleeding volume. The results show that there is no significant variation in foam settlement distance for different dilution ratios, and the difference in foaming ratio does not exceed 0.4 times. However, the bleeding volume is positively correlated with the dilution ratio of the foaming agent. At a dilution ratio of 60×, the bleeding volume is about 1.5 times greater than that at 40×, which reduces foam stability. Furthermore, an appropriate amount of sodium dodecyl benzene sulfonate improves both the foaming ability of the foaming agent and the stability of the foam. Additionally, this study investigates how the water-solid ratio affects the basic physical properties, water absorption, and stability of foamed lightweight soil. Foamed lightweight soil with target volumetric weights of 6.0 kN/m3 and 7.0 kN/m3 meet the flow value requirement of 170~190 mm when the water-solid ratio ranges are set at 1:1.6~1:1.9 and 1:1.9~1:2.0, respectively. With an increasing proportion of solids in the water-solid ratio, the unconfined compressive strength initially increases and then decreases after 7 and 28 days, reaching its maximum value when the water-solid ratio is between 1:1.7 and 1:1.8. The values of unconfined compressive strength at 28 days are approximately 1.5-2 times higher than those at 7 days. When the water ratio is excessively high, the water absorption rate of foamed lightweight soil increases, resulting in the formation of connected pores inside the material. Therefore, the water-solid ratio should not be set at 1:1.6. During the dry-wet cycle test, the unconfined compressive strength of foamed lightweight soil decreases, but the rate of strength loss is relatively low. The prepared foamed lightweight soil meets the durability requirements during dry-wet cycles. The outcomes of this study may aid the development of enhanced approaches for goaf treatment using foamed lightweight soil grout material.

Durability of MICP-reinforced calcareous sand in marine environments: Laboratory and field experimental study

As eco-friendly methods, microbial induced carbonate precipitation (MICP) method was used to reinforce the calcareous sand in the South China Sea in this paper. The durability characteristics and deterioration mechanism of MICP-reinforced calcareous sand under various environment factors were investigated synthetically based on the unconfined compressive strength, mass loss rate and microscopic morphology in laboratory and field experimental study. Results show that, the unconfined compressive strength value of the sample is only 35.19 % of the initial strength, while the mass loss rate is about 6.69 % after 30-days of field marine environment erosion. MICP-reinforced calcareous sand shows the strongest resistance to temperature cycles, followed by dry-wet cycles, coupling effect of temperature and dry-wet cycle and salt spraying with drying cycles. MICP-reinforced calcareous sand exhibits the worst resistance to the field marine conditions, but the integrity of the sample could still be maintained after 30-days of field tests. The deterioration mechanism of MICP-reinforced calcareous sand is consistent under the various environmental cycles. First, the weakly cemented calcium carbonate crystals on the sample surface fall off, and then the hard-shell layer on the sample surface became weaker under various erosion. Finally, the internal cemented structure of the sample was gradually destroyed. The results indicated the utilization value of the MICP method in ocean engineering, but it is necessary to enhance the performance of the MICP-reinforced calcareous sand to ensure its protective effect after a certain environmental impact cycle.

Machine learning models for predicting unconfined compressive strength: A case study for Precambrian basement complex rocks from Ado-Ekiti, Southwestern Nigeria

This study investigates the applicability of four distinct machine learning (ML) models – Random Forest (RF), Relevance Vector Machine (RVM), Support Vector Machine (SVM), and Artificial Neural Network (ANN) - for predicting the unconfined compressive strength (UCS) values of Precambrian basement rocks. The models employ input parameters such as rock aggregate index (Aggregate Crushing Value (ACV), Aggregate Impact Value (AIV), and Los Angeles Aggregate Value (LAAV)) and mechanical test index values (Schmidt Hammer Rebound Number (SHR) and Point Load Strength Index (IS(50)) for prediction purposes. Additionally, a multilinear regression (MLR) model was implemented to compare the predictive performance of the ML models against the traditional linear regression model. The developed models were validated using performance metrics such as Mean Absolute Error (MAE), Root Mean Squared Error (RMSE), and Adjusted R-Squared (Adj.R2). The Friedman statistical test was also employed to investigate the significance of the differences in the performance of the models. The results indicate that all the models performed well and showed better predictive performance compared to the MLR model during both the training and testing phases, except for the ANN model, which exhibited slightly poorer performance than the MLR model in the testing phase. However, the SVM model demonstrated the best predictive accuracy among all the models with MAE, RMSE, and Adj.R2 scores of 0.76 and 1.45; 1.16 and 1.8; 0.98 and 0.90, respectively, for the training and testing phases. The difference in the performance of the predictive models was statistically significant, as revealed by the Friedman statistical test. A feature importance analysis was conducted to verify the significance of each input parameter, revealing that all input features had a positive effect on the output of all the models. However, IS(50) had the most significant impact on the models.

The Effectiveness of Cement and Lime as Stabilizers for Subgrade Soils with High Plasticity and Swelling Potential

This study investigated the effects of cement and lime on the mechanical properties of subgrade soils, which are challenging to stabilize due to high plasticity and swelling potential. The study found that both cement and lime are effective stabilizing agents that increase the OMC, with cement being more effective in reducing the OMC of black cotton soil. The engineering properties of stabilized Chokocho subgrade soil were also evaluated, and the use of cement and lime as stabilizers was found to be effective in improving soil characteristics for subgrade applications. This was indicated by increased maximum dry density values, reduced plasticity index values, and increased California bearing ratio and unconfined compressive strength values. The chemical composition test demonstrated that calcium plays a significant role in soil stabilization, while aluminum can potentially affect soil stability negatively. Other elements such as magnesium, iron, silicon, zinc, and nickel contribute positively to soil stability. The low amounts of lead, copper, manganese, potassium, sulfur, and titanium present in the soil indicate a minor contribution to soil stabilization, but their impact on soil properties and plant growth cannot be ignored. Overall, the study highlights the importance of considering specific soil types and conditions when undertaking soil stabilization projects. The findings provide valuable information for future research in this field, particularly in investigating the effectiveness of other stabilizers and their interactions with specific soil types. The use of cement and lime in soil stabilization is an effective method for enhancing the strength and durability of weak soils, as shown by the reduction in plastic limit values observed in the stabilized soil samples. The appropriate content of cement and lime to use in soil stabilization could inform standards and codes for soil stabilization.

Effects of Dosage and Type of GGBS on the Mechanical Properties of a Hybrid Red-Mud Geopolymer

Bayer red mud (RM) is made from aluminum ore using the Bayer process and is considered an industrial waste. The storage of unused RM can cause environmental and geological problems. Although several studies have focused on RM geopolymers, the amount of RM consumed by these synthetic geopolymers is small (usually <50%). Therefore, in this study, a hybrid geopolymer material with more than 90% RM content was developed and made it possible to apply in engineering construction. The consumption of a considerable amount of RM would reduce the massive accumulation of RM and address the shortage of natural construction materials. Experiments were conducted with ground granulated blast-furnace slag (GGBS) as the activator. Two different active GGBSs were selected to stabilize the RM by geopolymerization. The effects of dosage and type of GGBS on the mechanical properties of RM were investigated by conducting unconfined compression tests and disintegration and compression experiments. The experimental results indicated that the type and dosage of GGBS had a significant effect on the mechanical behavior of RM. Based on the unconfined compressive strength (UCS) values and the results of the disintegration and compression experiments, the optimal RM-GGBS mixed geopolymer was determined by orthogonal analysis. Microscopic analysis showed that under optimal conditions, the amorphous phase participated in the geopolymerization process, forming an amorphous geopolymer that improved the mechanical properties of RM.