California Bearing Ratio Tests Research Articles

Strength improvement of clay subgrade soil stabilised with recycled concrete aggregate and granulated blast furnace slag

In this research, a combined method of chemical and physical stabilisation has been used to investigate the effect of using recycled concrete aggregate (RCA) and granulated blast furnace slag (GBS) in improving the strength properties of subgrade soil. A comprehensive series of compaction, uniaxial compressive strength (UCS) and California bearing ratio tests were performed on different mixtures. The results show that UCS values increased for clay subgrade with up to 20% RCA content and decreased after that. The subgrade soil with 20% RCA was treated with GBS to obtain the target uniaxial strength for stabilised subgrade soils. Also, the results obtained from investigating the effect of freeze–thaw cycle on the UCS of the optimum combination with different GBS content show that the F-T cycle reduces the value of the UCS from 32% to 53% after 12 F-T cycles.

Effect of Ground Nut Shell Powder on Soil Stabilization By IJISRT

Various varieties of soil may be found across the world. The engineering features of soil are the most significant consideration in any building development. Construction on expanding soil is the most essential difficulty that civil engineers encounter. The expansive soil has typically undesired engineering properties, such as poor shear strength, plasticity, and compressibility; it expands when wet and shrinks when dry. Its characteristics can be enhanced with appropriate stabilizing procedures. Black cotton covers around 15% of the soil in India. Crops produced on black cotton soil include pea nuts, cotton, wheat, jowar, linseed, tobacco, castor, sunflower, and millets. In comparison, the peanut industry generates millions of tons of garbage. Nowadays, a key issue is "How to benefit from the industrial waste product." Soil stabilization is performed in order to improve the engineering qualities of the soil. The rising expense of typical stabilizing chemicals, along with the need to economically utilize industrial and agricultural waste for positive engineering reasons, prompted an inquiry into the stabilizing potential of groundnut shell powder (GSP) in expansive soil. This study looks at how to improve the geotechnical characteristics of expansive soil by performing various tests such as specific gravity, atterberg limit, compaction test, and California bearing ratio test to determine the properties of the untreated soil sample and then adding 5%, 7%, and 9% ground nut shell powder by weight of soil. In this phase, only untreated soil testing are conducted. After receiving treated and untreated soil results, compare the untreated black cotton soil results to various percentages of ground nut shell powder results to determine the optimum amount of ground nut shell powder necessary to increase the stability of black cotton soil.

Utilization of waste face masks to reinforce magnesite mine tailings for sustainable subgrade construction

The disposal of magnesite mine tailings (MMT), a by-product of magnesite mining, raises significant environmental concerns due to its adverse effects on soil, water and air quality. Likewise, the improper disposal of used face masks exacerbates environmental burdens. The innovative use of polypropylene fibres (PPF) derived from disposable face masks to reinforce. This study explores the compaction and strength characteristics of PPF-MMT composites with varying fibre content to develop a sustainable composite for subgrade construction. The findings indicate that the addition of PPF increases optimal moisture content and decreases maximum dry density. Shear strength analysis reveals a linear failure envelope for both MMT and PPF-MMT, with initial angle of internal friction improvement at lower PPF content (0.25% and 0.5%) but a decline at higher contents (0.75% and 1%). Importantly, PPF-MMT consistently exhibits a unique strain-hardening behaviour across all stress levels, distinguishing it from MMT, which only transitions to strain-hardening at higher stresses. Under vertical load, MMT shows contraction, while the PPF-MMT composite initially contracts but later dilates due to increased fibre-MMT interaction during horizontal displacement. Furthermore, California bearing ratio (CBR) tests demonstrate increased dry CBR with PPF, reaching a peak of 33.85% at 0.5% fibre content. The soaked CBR tests affirm the remarkable durability of PPF-MMT, maintaining significantly higher values than MMT even after 60 days of soaking. The study concludes that 0.5% fibre content as optimum dosage.

Plastic as a Soil Stabilizer

Soil stabilization is any process which improves the physical properties of soil, such as increasing shear strength, bearing capacity etc. which can be done by use of controlled compaction or addition of suitable admixtures like cement, lime and waste materials like fly ash, phosphogypsum etc. The cost of introducing these additives has also increased in recent years which opened the door widely for the development of other kinds of soil additives such as plastics, bamboo etc. This new technique of soil stabilization can be effectively used to meet the challenges of society, to reduce the quantities of waste, producing useful material from non-useful waste materials. Use of plastic products such as polythene bags, bottles etc. is increasing day by day leading to various environmental concerns.Therefore the disposal of the plastic wastes without causing any ecological hazards has become a real challenge. Thus using plastic bottles as a soil stabilizer is an economical utilization since there is scarcity of good quality soil for embankments. This project involves the detailed study on the possible use of waste plastic bottles for soil stabilization. The analysis was done by conducting plate load tests on soil reinforced with layers of plastic bottles filled with sand and bottles cut to halves placed at middle and one-third positions of tank.The comparison of test results showed that cut bottles placed at middle position were the most efficient in increasing strength of soil. The optimum percentage of plastic strips in soil was found out by California Bearing Ratio Test and using this percentage of plastic, plate load test was also performed. The size and content of strips of waste plastic bottles have significant effect on the enhancement of strength of the soil].

Utilization of Nano Silica and Plantain Leaf Ash for Improving Strength Properties of Expansive Soil

This study investigates the effect of nanosilica and plantain leaf ash on the sustainable stabilization of expansive soil. This study conducted various strength tests, including Unconfined Compressive Strength (UCS), direct shear, and California Bearing Ratio (CBR) tests, to analyze the enhancement of mechanical properties by adding nano silica and plantain leaf ash. Scanning Electron Microscopy (SEM) analysis was conducted to investigate the interaction mechanism between the soil and the combination of nano silica and plantain leaf ash. Three different combinations of plantain leaf ash were utilized, ranging from 5% to 15%, alongside nano silica ranging from 0.4% to 1.2%. The reinforced soil’s compressive strength, shear strength, and bearing capacity were assessed through UCS, direct shear, and CBR tests. The results demonstrated significant improvements in compressive strength, up to 4.6 times, and enhancements in cohesion and frictional angle, up to 3.3 and 1.6 times, respectively, at 28 days. Moreover, the addition of nano silica and plantain leaf ash led to increased bearing capacity and reduced soil swelling potential, contributing to the overall stability and strength improvement in expansive soil. The SEM test results demonstrate that maximum bonding and compaction occur when 1.2% nano silica and 15% plantain leaf ash are added to the soil.

ENHANCEMENT OF SUB GRADE SOIL BY USING FLYASH AND LIME

Abstract -In India 15% of land is covered by Black Cotton Soil. The presence of montmorillonite clay mineral in the Expansive soil causes Swelling and shrinking properties which leads to major problems in Construction sites. This can be resolved by using soil stabilization techniques which enhances the engineering properties of soil. The soil stabilization is most important for the construction which is widely used in pavements or any other structures on expansive soil. Utilization of industrial waste materials in the improvement of soils is cost-efficient and eco-friendly method. In the present study an experimental investigation is taken to know the Geotechnical Characteristics of Expansive Soil with the Combination of FLYASH and LIME. In this study soil is mixed with the different proportions of (10%,20%,30% & 40%) FLYASH and (2.5%,5%,7.5%,10%,12.5% & 15%) LIME. The strength gained by soil is investigated by conducting California bearing ratio test & it is also calculated to reduce the thickness of the layer. The maximum dry density increased from 1.38g/cc to 1.54g/cc. The CBR un soaked test value enhances from 1.01% to 6.49% respectively Key Words: Black Cotton Soil, Fly ash, Lime, Compaction, maximum dry density, CBR

Research on correlation between dynamic resilient modulus and CBR of coarse-grained chlorine saline soil

A large area of coarse-grained saline soil is distributed in saline soil areas, and chlorine saline soil with a high salt content is a typical representative. The dynamic resilient modulus was accurately predicted using the California-bearing ratio (CBR) value to determine the relationship between the dynamic resilient modulus of coarse-grained chloride saline soil and its CBR value. Indoor dynamic triaxial tests and CBR tests were conducted to investigate the evolution of the dynamic resilient modulus (MR) and CBR of coarse-grained chlorine saline soil under the influence of the stress level, water content, and salt content. The test results showed that the dynamic resilient modulus increased with an increase in the confining pressure and bulk stress and decreased as the deviator stress increased; however, the CBR increased with an increase in the corresponding unit pressure. The higher the salt and water contents, the more obvious the influence of stress on the dynamic resilient modulus and CBR value. Under the same stress level, the decrease in the dynamic resilient modulus and CBR gradually increased with increasing salt and moisture content, and the effect of salt tended to be more significant than that of water. Based on the correlation between the dynamic resilient modulus and CBR revealed by the experiment, a more widely applicable model was selected from the existing theoretical models related to CBR for the regression analysis of the test data, and a prediction model of the dynamic resilient modulus based on the CBR value was proposed (MR = 21.06CBR0.52). This prediction model had a high correlation coefficient (R2 = 0.893) and could effectively predict the dynamic resilient modulus of coarse-grained chlorine saline soil using CBR values. The results provide a simple and reliable method for determining the design parameters of a coarse-grained saline soil subgrade.

Soil-geogrid interaction: The shear zone thickness of seafloor sediments with geogrid compared to filling materials

In geotechnical applications close to marine areas, using soil with rounded gravel that waves have left on the seafloor as fill material can help ensure the sustainable use of natural resources. However, typical fill materials have more shear strength than rounded sediments, but geogrids can solve the issue. Nevertheless, it is not well known how the grains’ shape factors will affect the soil-geogrid interlocking mechanism and how the soil-geogrid interlocking based on grain shape will vary in the soil above and below the geogrid. This study aims to address the ambiguities specified. Therefore, three soil specimens were acquired, and the grains’ shape parameters were determined using image processing. Subsequently, soil specimens were tested using large-scale direct shear (LSDS) and California Bearing Ratio (CBR) tests. Besides, LSDS tests were conducted by placing the geogrid at the shear surface, at different depths beneath the shear surface, and at varying levels above the shear surface to assess the soil-geogrid interaction distance. The findings showed that soil with seafloor gravels, using geogrid, could have the same shear strength as soil with crushed aggregates. Also, the highest shear strength was achieved when the geogrid was located below the shear surface by the maximum grain diameter.

Improvement of subgrade California Bearing Ratio (CBR) using recycled concrete aggregate and fly ash

The study aims to understand the effect of different admixtures on improving the quality of flexible pavement subgrades. In this paper, recycled concrete aggregates (RCA) and Fly Ash were used as the admixtures in improving the maximum dry density (MDD), swelling potential, and California bearing ratio (CBR) of subgrade soil. The percentages of RCA and fly Ash used were 5%, 10%, and 15%. With the upscaling in fly ash dosage, the optimum moisture content and the California bearing ratio increased. However, the MDD of soil decreased for higher fly ash contents. On the contrary, the optimum moisture content (OMC) of the soil decreased and the MDD and California Bearing Ratio increased with an increase in RCA content. Both RCA and fly ash-treated soil demonstrated lower values of swelling. At 5% dosage, both RCA and fly ash admixtures were found to improve CBR. However, at higher percentages (10% and 15%) of fly ash, the CBR values decreased while in comparison, soil samples performed significantly better in the CBR test with the increasing dosage of RCA. The findings of this research can be used to examine the suitability and effects of recycled aggregate and fly ash on the performance of soil in terms of CBR, particularly when the soil is planned to be used as a subgrade in highways.

Design and mechanic analysis of asphalt pavements with subgrade reinforced using the AEMC software

The Construction industry is one of the major contributors to waste generation in various aspects of its production chain. Construction and Demolition Waste (CDW) stand out, generated by the lack of reuse and inadequate disposal, as well as a lack of knowledge about the potential uses of this material. Thus, this article presents a methodology for the use and design of asphalt pavement layers that use CDW as coarse aggregate and/or infrastructure layer. In this context, a mechanical analysis of the material used as a subgrade reinforcement in asphalt pavements for roads is carried out. In this sense, the study promoted the California Bearing Ratio (CBR) test of recycled aggregate, and subsequently, empirical design was performed using the DNIT method and mechanistic structural evaluation using the MeDiNa AEMC. The results of stresses, strains, and displacements reveal that the material can partially replace the simple granular gravel (BGS) as a sub-base material, contributing positively to the structural performance of the road infrastructure. It should be noted that this is a preliminary study, but the use of the material may be of interest in the short and medium term, significantly contributing to another way of useful and conscious disposal, bringing sustainability to the Construction industry.

Building MLR, ANN and FL models to predict the strength of problematic clayey soil stabilized with a combination of nano lime and nano pozzolan of natural sources for pavement construction

The current study aims at predicting the strength of the problematic clayey soils treated with combinations of pozzolan of natural sources and lime powder when added as soil additives at a nano scale. Multiple linear regression (MLR), artificial neural networks (ANN) and fuzzy logic (FL) tools were employed in the analytical study. The variables of the present study include the following: nano pozzoaln of natural source (NNP) content, nano lime content (NL), median particle size of NNP, active silica content of NNP (SiO2active), Initial liquid limit (ILL) and initial plastic limit (IPL) of the investigated soils. NNP was added at five percentages, i.e. 0%, 0.5%, 1%, 1.5% and 2%, while NL was added at five percentages, i.e. 0%, 0.3%, 0.6%, 0.9% and 1.2%. Three median particle sizes namely 50, 100 and 500 nm size were studied. Based on the different investigated soils and combinations, 120 soil mixtures were prepared and tested. California bearing ratio (CBR) and plasticity index (PI) were particularly examined. CBR tests were conducted at a soaked condition on specimens compacted to a maximum dry density (MDD) at the optimum moisture content (OMC). PI values were obtained following the Atterberg limits test. Based on the results of the performance criteria of the developed predictive models, it can be concluded that the CBR and PI of the expansive clayey soils can be effectively predicted using ANN and FL techniques. The results obtained by MLR were far from those obtained by both ANN & FL. In addition, ANN tool was slightly more accurate than FL as far as prediction of CBR and PI is concerned. The higher capability of ANN & FL models in predicting CBR & PI values, which generally obtained through time-consuming and expensive tests, could be useful for geotechnical engineers to assess or design a new pavement project. Further, it is recommended to do a re-evaluation of the current study in future, particularly when more data is available in the literature.

Bearing capacity of Percut Sei Tuan clay stabilized with palm shell ash

Improvements to the bearing capacity of the soil have been carried out and developed at this time, one of which is the stabilization of clay soils. There are several alternatives to solve low soil bearing capacity, one of which is using geo-synthetic materials but has a weakness in terms of high cost. Another alternative is to add palm shell ash as a stabilizing agent. The effect of adding palm shell ash has not been thoroughly studied, so further research is needed. The material added is palm shell ash with a variation of 0%, 4%, 8%, 10%, and 12% in each test. The tests carried out in the laboratory were water content (w), specific gravity test (Gs), Atterberg limit test, sieve analysis (sieve analysis), soil compaction test, and CBR (California Bearing Ratio) test. The CBR test was carried out by curing the soil for 1, 3, 5, and 7 days with a mixture of palm shell ash before compaction. The soil in this study belongs to the A-7-5 group. The CBR (California bearing ratio) value increased with the increase in the palm shell ash percentage in the mixture after curing the soil. The highest CBR value was in the variation of 12% palm shell ash with a 7-day curing period of 6.92% with a soil bearing capacity of 5.06.

Natural Gradient Boosting for Probabilistic Prediction of Soaked CBR Values Using an Explainable Artificial Intelligence Approach

The California bearing ratio (CBR) value of subgrade is the most used parameter for dimensioning flexible and rigid pavements. The test for determining the CBR value is typically conducted under soaked conditions and is costly, labour-intensive, and time-consuming. Machine learning (ML) techniques have been recently implemented in engineering practice to predict the CBR value from the soil index properties with satisfactory results. However, they provide only deterministic predictions, which do not account for the aleatoric uncertainty linked to input variables and the epistemic uncertainty inherent in the model itself. This work addresses this limitation by introducing an ML model based on the natural gradient boosting (NGBoost) algorithm, becoming the first study to estimate the soaked CBR value from this probabilistic perspective. A database of 2130 soaked CBR tests was compiled for this study. The NGBoost model showcased robust predictive performance, establishing itself as a reliable and effective algorithm for predicting the soaked CBR value. Furthermore, it produced probabilistic CBR predictions as probability density functions, facilitating the establishment of reliable confidence intervals, representing a notable improvement compared to conventional deterministic models. Finally, the Shapley additive explanations method was implemented to investigate the interpretability of the proposed model.

Model tests on ordinary and geosynthetic encased stone columns with recycled aggregates as filler material

PurposeSincethe availability of natural aggregates is very sparse, recycled industrial and construction waste provides a sustainable alternative to ground improvement using vibro replacement method. Utilizing recycled building waste caters the requirement for its disposal and offers an effective remedy for the scarcity of natural resources. The aim of this study was to give a sustainable alternative for the natural aggregates as the material for stone column.Materials and methodsA good stone column material should be hard, dense, chemically inert and must comply with the size requirement. The utilization of construction debris and spent railway ballast as column material has been the subject of numerous researches. This work focuses on finding the suitability of railway ballast and concrete debris as alternatives for stone column material. A detailed laboratory testing of these materials has been carried to judge their strength requirements as the material for both Ordinary Stone Columns (OSCs) and Geosynthetic Encased Stone Columns (GESCs). The improvement in capacity of both OSCs and GESCs is evaluated by performing California Bearing Ratio (CBR) test in laboratory by creating unit cell stone column models of different recycled aggregates and comparing their load settlement behavior with natural aggregates.Results and discussionRailway ballast, natural aggregates, concrete debris and virgin soil were found to show decreasing order in CBR test results. Loading required for causing settlement in both OSCs and GESCsshowed remarkable increase as compared to that of virgin clay and the maximum load settlement improvement was observed for railway ballast in both the types of stone columns. The CBR values for GESC made from railway ballast, natural aggregates and concrete debris were 54, 49 and 38% respectively. On the other hand, CBR for OSC made from railway ballast, concrete debris and natural aggregates were found to be 25.5, 20.4 and 24% respectively and CBR of virgin clay was found to be just 11%.ConclusionThe demonstrated application of sustainable sources in place of natural aggregates provides a crucial pathway for utilizing the recycled aggregates as stone column filler material. Up on encasing the OSC with geotextile the performance of stone columns has improved appreciably in terms of load capacity. Railway ballast and concrete debris can be adopted as an alternate for the natural stone column materials to improve the bearing capacity of site consisting mainly of soft clays.

Utilization of Earthquake Demolition Wastes and Afşin–Elbistan Fly Ash for Soil Improvement after the Kahramanmaraş Earthquake (6 February 2023)

Türkiye is surrounded by active faults that have the potential to produce big earthquakes. Recently, one of these faults has become active. Two earthquakes of magnitude 7.7 and 7.6 occurred 9 h apart on 6 February 2023 in Kahramanmaraş. It is reported that 150 million tons of earthquake demolition waste (EDW) is estimated to be produced as a result of those natural hazards. This waste poses a serious risk to both the environment and human health. Its use in geotechnical applications will provide serious environmental benefits. In this study, Afşin–Elbistan fly ash (AEFA) and EDW were used to stabilize weak clayey soils in different proportions. Samples were prepared by separately adding 5, 10, 15, and 20% AEFA and EDW to high-plasticity clay. The AEFA used in this study was used because the production of AEFA is too high, and it is not used in concrete production because it does not comply with the standards and causes serious environmental problems for the region. The Atterberg limit, standard compaction, unconfined compression strength (UCS), triaxial, and California bearing ratio (CBR) tests were performed on soil samples, and samples were prepared from soil mixtures with various proportions of AEFA and EDW added. In addition, clay mixtures were prepared with EDW by keeping the AEFA ratio constant at 15% and their effects were also investigated. According to Atterberg test results, the natural soil class was determined as high-plasticity clay, the soil class of the mixtures created by adding EDW and AEFA was determined as low-plasticity clay, and all ternary mixtures were determined as low-plasticity silt. In addition, the maximum dry density increased for all mixtures, while the optimum water content decreased. A significant increase was observed in UCS test results, especially in ternary mixtures. While cohesion increased in AEFA mixtures, it decreased in ternary mixtures as the EDW ratio increased. It was observed that the internal friction angle increased in all mixtures. According to CBR test results, it was determined that the binary AEFA mixture ratio was 20%, the binary EDW mixture ratio was 10% and above, and all ratios of the ternary AEFA + EDW mixtures could be used as road sub-base material. After the major earthquake disaster, the use of EDW is of great importance for the environment. As a result, AEFA and EDW were found to enhance the geotechnical properties of clay.

Utilization of Plastic Waste in Reinforcing Sandy Soil for Sustainable Engineering Applications

Large quantities of polyethylene terephthalate (PET) plastic are discarded into the environment during production, application, and disposal. Although current clean-up strategies aim to mitigate the adverse impacts of PET pollution, efforts struggle to keep up with the escalating amount of PET waste. This accumulation of PET waste poses significant threats to ecosystems worldwide. One recycling method for PET plastic waste involves its utilization in soil reinforcement applications within civil engineering. By incorporating PET plastic waste to reinforce poor-quality sands, sustainable construction practices can be promoted in civil engineering infrastructures, addressing multiple aspects of sustainability, including engineering, economic, social, and environmental considerations. The experimental work conducted in this research involved sieve analysis, proctor compaction test, California Bearing Ratio (CBR) test, and direct shear box test. The sand was reinforced with varying percentages of PET plastic waste flakes, namely 5, 10, and 15 %, with respect to the weight of the soil sample taken for the test, and laboratory tests were performed on the samples. Including PET plastic flakes enhanced various soil properties, such as shear strength and friction angle. It also improved the CBR value of the composite, making it suitable for pavement construction. The reduction in dry density further supports the application of the composite in lightweight structures. In conclusion, the geotechnical material obtained from the soil-PET plastic waste composite can be utilized in various geotechnical projects, including landfills and slope stabilization.

The usage of marginal aggregate as subbase layer

Aggregate holds the main role in determining the quality of pavement layers. Unfortunately, the locally available aggregates sometimes did not pass one or more requirements stated in the standard, making these aggregates technically unable to be used. These aggregates are called marginal or substandard aggregates. However, previous research projects have shown the potential of utilizing marginal aggregates as pavement layers. This research aims to analyst the techniques for utilizing marginal aggregates as pavement layers, specifically as subbases. Two techniques were evaluated herein, namely by varying the aggregate gradation and by adding cement and lime as stabilizers, and the specimens were assessed by the California Bearing Ratio (CBR) test. The research results found that varying the percentage of coarse and fine aggregates in the specimens improved the CBR value. The specimen obtained the highest CBR value with 70% coarse aggregate and 30% fine aggregate. Moreover, it was found that adding cement and lime as stabilizers at the right percentage was also able to improve the CBR value of the specimens and mixing the stabilizers beyond a certain percentage decreases the CBR value. The amount of cement and lime needed depended on the aggregate gradation used.    

Geotechnical Properties of Cement-Stabilized Lateritic Soil with Bamboo Leaf Ash in the Takie Area of Ogbomoso

This paper presents findings related to the impact of Bamboo Leaf Ash (BLA) and cement stabilization on the lateritic soil in the Takie Area of Ogbomoso. The study employed various testing methodologies to assess soil characteristics, particle size distribution, and California Bearing Ratio (CBR) under different stabilization conditions. Chemical analysis compared Ordinary Portland Cement (OPC) and BLA, demonstrating distinct differences between the two materials. The results of particle size distribution affirmed an intermediate, moderately graded soil with low clay content primarily comprising sand and gravel. The CBR tests unveiled the considerable influence of cement and BLA percentages on the soil's bearing capacity in both unsoaked and soaked conditions. Notably, the introduction of 2% cement displayed the highest CBR value, especially when paired with 10% BLA, showing promising results for soil strength enhancement. Conversely, the impact of BLA on soil strength in soaked conditions was less pronounced. This research provides valuable insights into the use of BLA and cement stabilization in lateritic soil, contributing to the understanding of soil behavior for engineering applications. Keywords: Geotechnical Properties, Cement Stabilization, Lateritic Soil, Bamboo Leaf Ash, California Bearing Ratio. Aims Research Journal Reference Format: Obakin, O. A., Oladunmoye, O.M., Ajayi, S.A.. & Taiwo J.B. (2023): Geotechnical Properties of Cement-Stabilized Lateritic Soil with Bamboo Leaf Ash in the Takie Area of Ogbomoso. Advances in Multidisciplinary and Scientific Research Journal Vol. 9. No. 4. Pp 19-26. . www.isteams.net/aimsjournal. dx.doi.org/10.22624/AIMS/V9N4P2

Identifying the microstructure and mechanical properties of expansive soil stabilized using fly ash and waste foundry sand

Expansive soil causes road construction damage in the form of cracks or deformations due to changes in moisture content. One method to address this issue is soil stabilization using additive materials. Special additives can sometimes be expensive; hence it is necessary to use additive materials based on industrial waste as a waste management solution to solve the problem of expansive soil as a road construction subgrade. This study aims to analyze the effects of adding two types of industrial waste, namely fly ash (FA) and waste foundry sand (WFS), regarding the microstructure, physical, and mechanical properties of expansive soil. The method of stabilizing expansive soil involves mixing the soil with 9 % FA and various levels of WFS (0 %, 7.5 %, 10 %, 15 %) based on the dry weight of the soil. Microstructure testing includes quantitative X-ray diffraction and scanning electron microscopy. Physical property testing includes specific gravity, Atterberg limits and sieve analysis. Mechanical testing, i.e. compaction, California Bearing Ratio, swelling, and Triaxial tests were conducted. Soil stabilized with 9 % FA and 15 % WFS shows a significant increase in the internal friction angle and cohesion, reducing swelling by 67.18 % compared to the original soil swelling. The addition of 9 % fly ash and 15 % WFS to expansive soil reduces the content of montmorillonite. Natural expansive soils have a very poor soaked CBR of 0.94 %, while stabilized soils with 9 % FA and 15 % WFS have a soaked CBR of 6.46 %. This means that the soaked CBR of the stabilized soil meets the minimum CBR required for road subgrade construction. A mixture of 9 % FA and 15 % WFS in expansive soil can be recommended as a material for stabilizing expansive soil due to its ability to improve microstructure and mechanical properties

Cost Comparison of Flexible Pavement on Weak Sub-Grade Soil Modified with Lime and SD

The effectiveness of flexible pavement is affected by the subgrade quality. The subgrade refers to a compacted layer of soil that provides sideways support to the pavement. When constructed on a weak subgrade, it negatively impacts the pavement's performance, leading to a shorter lifespan. Traditionally, the common method to stabilize a soft subgrade involves removing the weak soil and replacing it with stronger soil. However, due to the high expenses associated with soil replacement, highway agencies are exploring alternative approaches to constructing highways on soft subgrades. Soil stabilization is a commonly employed alternative in pavement construction, serving as an effective method to enhance the engineering characteristics of soil, including its strength and stability. This paper focuses on the utilization of lime and stone dust (SD) as admixtures for an efficient ground improvement technique over weak subgrade soil deposits. The California Bearing Ratio (CBR) test is conducted by making the specimens of weak subgrade by adding the variable percentages of a mixture of lime and SD. First, the soil was mixed up with lime to 12% by weight with an increment of 3% again the soil was mixed with SD with increments of 10% up to 50% by weight of soil. The study determined an optimal lime content of 3% based on the geotechnical properties of the mixture and the cost considerations of lime and the weak subgrade. Following this, SD was added to the optimized lime-weak subgrade mixture in varying increments of 10% by weight, up to a maximum of 40%. The modified mixes were then evaluated for their CBR and maximum dry density values. The CBR is increased to 15% and the total pavement thickness decreased to 725 mm for 50% SD addition with 4.89 % in cost reduction.