Subgrade Stabilization Research Articles

Mechanical, freeze-thaw resistance and heavy metals leaching properties of alkali-activated recycled concrete powder solidified sludge

Solidified sludge was an efficient method to consume the large amount of sludge, which can be used as the subgrade filler in road engineering. However, the traditional solidified materials, such as cement and lime, consumed a large amount of natural resources and increased carbon emissions. This study used the alkali-activated recycled concrete powder (ARCP) to solidify sludge, which could be used as a potential subgrade stabilization filler. The optimal factors of ARCP were firstly determined by orthogonal test according to the compressive strength. Then the influences of different ARCP dosage, sludge moisture content and curing method on the mechanical properties, freeze-thaw resistance and heavy metals immobilization of the ARCP solidified sludge (ARCPS) were investigated. At last, microstructures of ARCPS were analyzed by SEM, XRD and TG-DTG tests. The experimental results demonstrated that the optimal mixture for ARCP: the silicate modulus of 1, liquid-solid ratio of 0.48 and calcium hydroxide content of 3 %. The solidified process by ARCP improved the mechanical properties and freeze-thaw resistance of ARCPS greatly. The 7 d unconfined compressive strength of ARCPS could reach 1305–2033 kPa when the sludge moisture content was 15 %, which meet the requirement of 500 kPa from the Chinese standard. The frost heaving rates of ARCPS were between non-frost heaving and mild frost heaving. The sludge moisture content was the most important factor affecting the freeze-thaw resistance of ARCPS. The properties of ARCPS were further improved after carbonation curing. The leaching mass concentration of heavy metals decreased significantly after the solidification of sludge. After 5 freeze-thaw cycles, the heavy metal leaching concentration increased but was still met the requirement of standards. SEM results showed that the surface of carbonated ARCPS was covered by dense scale-like carbonation products, which further enhanced the strength and freeze-thaw resistance of ARCPS. The results can be used to guide the application of sludge and ARCP in construction.

Subgrade Stabilization for Flexible Pavements Employing Recycled Asphalt and Pozzolana

Subgrade Stabilization for Flexible Pavements Employing Recycled Asphalt and Pozzolana

Design of sustainable bituminous concrete pavement with cement–treated granular layers constructed on stabilized subgrade

Purpose Designing a sustainable bituminous concrete with long-term performance is a challenging problem. In addition, strength of the subgrade has a crucial impact on pavement design. This paper aims to concentrate on subgrade soil stabilization with granite dust powder (GDP) and crumb rubber powder (CRP) to improve the engineering properties of the soil. Further design of bituminous concrete pavement with cement-treated layers in base and subbase course layers was carried out with life cycle cost analysis and life cycle assessment for 1 km of a four-lane national highway. Design/methodology/approach Subgrade soil stabilized with GDP and CRP is characterized as per Indian Standards (IS)-2720 to determine the optimum dosage. Further, the mechanistic-empirical pavement design was carried out using Indian Road Congress-37 (2018), analyzed using IITPAVE software and validated with ANSYS software. The life cycle cost analysis is carried out using the net present value method, and the life cycle assessment is performed according to the cradle-to-grave approach. Findings A soil mix comprising 10% GDP and 2.5% CRP yielded a soaked California bearing ratio value of 6.58%. In addition, the design of bituminous concrete pavement with cement-treated granular layers showed a 26.9% reduction in life cycle cost and 59.4% reduction in total carbon footprint per kilometer compared to the pavement with traditional aggregate layers. Originality/value The research on subgrade stabilization with sustainable materials like GDP and CRP incorporating mechanistic empirical pavement design, life cycle cost analysis and life cycle assessment is limited. Overall, the study recommends the use of GDP and CRP to stabilize soil for subgrade application and incorporate cement-treated granular layers, which offer economic and environmental benefits compared to traditional pavement construction.

Freeze-Dried β-Glucan and Poly-γ-glutamic Acid: An Efficient Stabilizer to Strengthen Subgrades of Low Compressible Fine-Grained Soils with Varying Curing Periods.

The freeze-drying of biopolymers presents a fresh option with greater potential for application in soil subgrade stabilization. A freeze-dried combination of β-glucan (BG) and γ-poly-glutamic acid (GPA) biopolymers was used to treat low compressible clay (CL) and low compressible silt (ML) soils in dosages of 0.5%, 1%, 1.5%, and 2%. The California bearing ratio (CBR) test for the treated specimens was performed under three curing conditions: (i) thermal curing at 60 °C, (ii) air-curing for seven days followed by submergence for 4 days, and (iii) no curing, i.e., tested immediately after mixing. To investigate the influence of shear strength on the freeze-dried biopolymer-stabilized soil specimens and their variations with aging, unconfined compressive strength (UCS) tests were conducted after thermal curing at 60 °C for 3 days, 7 days, and 7 days of thermal curing followed by 21 days of air curing. The maximum CBR of 125.3% was observed for thermally cured CL and a minimum CBR of 6.1% was observed under soaked curing conditions for ML soils. Scanning electron microscopy (SEM), infrared spectroscopy, average particle size, permeability, and adsorption tests revealed the pore filling, biopolymer adsorption and coating on the soil surface, and agglomeration of the soil along with the presence of hydrogen bonds, covalent amide bonds, and Van der Waals forces that contributed to the stiffening of the stabilized soil. Using three-dimensional (3D) finite element analysis (FEA) and layered elastic analysis (LEA), a mechanistic-empirical pavement design was carried out for the stabilized soil and a design thickness catalog was prepared for the maximum CBR. The cost reductions for a 1 km section of the pavement were expected to be 12.5%.

Subgrade stabilization for road foundation in application for inundated area in Perlis, Malaysia

Abstract Inundated areas, which are prone to frequent flooding, pose significant challenges for road infrastructure due to the adverse effects of water on subgrade soils. Thus, the objectives of this research were to identify and characterize the soil type from roadside of Kampung Bakau, Kangar, Perlis, and evaluate and propose the effective subgrade stabilization methods to enhance the performance and durability of road foundations under such condition. In this research, atterberg limit, standard proctor, and california bearing ratio (CBR) tests were conducted. For CBR test, 6 sets of soil samples were considered. In addition, during the CBR tests, soaked and unsoaked method were performed to simulate the condition of flooding. In general, the soil samples taken were characterized as high plasticity silt. Besides that, the results obtained from CBR test showed that lime with 8 % addition in mixture provides the highest strength which was 4.50 kN of load resisted at 2.00 mm penetration. Meanwhile, cement with 3 % addition in mixture showed the lowest strength observed in the CBR test which was 1.75 kN. In conclusion, this research showed that for high plasticity silt type of soil, the optimized subgrade stabilization method is by lime with 8 % addition in mixture.

Coal ash as a natural additive for subgrade stabilization in the construction of low-volume traffic roads

The road network in Colombia, as reported by the National Roads Institute of Colombia (INVIAS), comprises a total of 206,708 kilometers, with 142,284 kilometers falling under the rural roads with low traffic volume network category. Sadly, an estimated of 96% of these roads are in poor condition. The primary reason behind this issue is the presence of subgrades that exhibit inadequate mechanical performance, largely due to the lack of proper stabilization methods. Moreover, these roads often serve as the sole access and exit routes for rural communities, significantly impacting their connectivity with nearby urban centers. Recognizing this critical issue, this article proposes the use of coal ash for subgrade stabilization during the construction of low-traffic-volume roads. The study conducted demonstrates that coal ash can enhance the mechanical properties of subgrades, leading to an increase in strength and load-bearing capacity. The improved mechanical properties are attributed to the binding and reactive characteristics displayed by the coal ashes, which greatly contribute to soil stabilization. To verify these claims, a series of physical, mechanical, and strength characterization tests were conducted on both natural and treated clayey sand samples obtained from a rural population in Colombia. The detailed analysis of the results shows an improvement in the mechanical properties of the soil due to the use of coal ash as a stabilizing agent.

Soil improvement withsugarcane bagasse ash : technical-economic viabilityfor tertiary roads

Introduction: Economic evaluation of soil subgrade improvement using sugarcane bagasse ash case study: Propal Road - La Cabaña Sugar Mill”, developed at the Pontifical Javeriana University of Cali in 2022. Problem: Tertiary roads in Colombia are essential for mobility in rural areas and for the sugar industry, which generates waste such as sugarcane bagasse ash (SGBA). Objective: To present the results of the economic and technical feasibility study of using sugarcane bagasse ash for soil improvement in tertiary roads. Methodology: Characterization tests of natural soil state and modified Proctor, expansion index, CBR, and unconfined compression for stabilized soils at percentages of 5, 10, 15, and 20% of SGBA are carried out. Results: The mechanical properties of the soil improve with additions of ash between 5% and 15%; however, the utilization of 15% of SGBA is proposed to favor the disposal of a significant volume of this waste. Conclusion: The technical and economic feasibility of using SGBA as a promising solution to improve tertiary roads in Colombia is demonstrated. Originality: Viability of implementing sugarcane bagasse ash on rural roads of sugar mills and agricultural areas with production of this type of waste. Limitations: Similar studies should be carried out for each region to confirm the appropriate percentage for subgrade stabilization using SGBA.

Effect of stabilizing subgrade layer using various additives on the flexible pavement design

Soil stabilization involves enhancing the physical properties of soil to increase its stability, durability, and ability to support heavy loads, making it a crucial technique in civil engineering and construction. The process is used to reduce soil permeability and compressibility and increase its shear strength. To achieve this, various additives are used. This paper evaluates RoadCem (nanomaterial) and traditional additives such as cement, lime, and ashes materials such as rice husk ash (RHA) and fly ash (FA) as by-product materials in clayey soil stabilization. The used percentages of Lime were (2, 4, 6, and 8%), cement and RoadCem (3, 6, 9, and 12%), FA (3, 6, 9, 12, and 15%), and RHA (5, 10, 15, 20, and 25%) by dry weight of the tested soil. Various tests were used to examine and evaluate the physical and engineering characteristics of the treated soil, modified proctor, atterberg limits, free swelling (FS%), unconfined compressive strength (UCS), California bearing ratio (CBR), and resilient modulus (Mr) as well as microstructure tests [scanning electron microscopic (SEM)]. All admixtures were tested and subjected to two curing periods, 7 and 28 days. The results indicated that the optimum additives percentages were selected as 6% FA and 15% RHA activated by 6% lime and 6% for both RoadCem and cement. At these percentages, plasticity, FS%, and optimum moisture content (OMC) values were decreased. In contrast, maximum dry density (MDD), UCS, CBR%, and Mr values were increased. In addition, the correlation between Mr and both CBR and UCS was drawn. SEM results showed that major changes were observed in the microstructure of treated samples due to the forming of cementitious materials. The study evaluated the effect of subgrade stabilization on reducing base layer thickness under light, medium, and heavy expected traffic loads with an economic analysis to examine the benefits of subgrade stabilization. The cost analysis showed that the optimal economic additives were RoadCem and cement.

Geopolymer Production From Waste Polyethylene Terephthalate and Glass For Clay Subgrade Stabilization

In this study, the efficacy of Polyethylene Terephthalate (PET) and Waste Glass Powder (WGP) as soil stabilizers was investigated to address the research questions and objectives. It examines the enhancement of mechanical strength of clayey subgrade soils sourced from Ogun state, Nigeria across varying proportions (5% −20%) including the potential cost analysis. Providing experimental insights into soil stabilization using PET individually and in combination with WGP-based geopolymers. Optimal stabilization was achieved at 5% PET, accompanied by 5%-20% WGP, and activated with a 2M NaOH solution. Results demonstrated enhanced mechanical strength with both stabilizers, with the combination of PET and WGP proving the most effective. Specifically, stabilization with 5% PET (1.18mm) WGP geopolymer, activated with 2% NaOH, yielded optimal results, exhibiting UCS values ranging from 180kN/m2 to 320kN/m2, surpassing cement-based stabilization (UCS value: 380kN/m2). Moreover, durability testing revealed significant improvements, with PET+WGP samples displaying a UCS mean of 259.4kN/m2, a weight of 89.67g, and a percent change in mean and weight of −25.79% and −25.86%, respectively, compared to cement-stabilized soil (UCS mean: 408.66 kN/m2, percent change: 2.15%, weight mean: 109.25g, percent change: -25.86%). Furthermore, PET+WGP exhibited a 125% increase in CBR compared to PET alone and a better cost reduction of $6,153,850,000.00 for 100km, highlighting its superior performance and cost reduction. The findings of this study hold significance for informed decision-making in material selection for road pavement works, offering an alternative method and contributing to Sustainable Development Goals and Circular Economy initiatives by advocating sustainable waste management and road infrastructure.

CONSTRUCTION OF SUSTAINABLE ROADS USING THE MIXTURE OF ALKALI-ACTIVATED RICE HUSK ASH AND FLY ASH

Soil stabilization, crucial for enhancing the stability and engineering properties of soil, has been the subject of extensive research utilizing mechanical and chemical methods. This study delves into the challenges faced in traditional soil subgrade stabilization methods, stemming from factors such as soil erosion, inadequate load-bearing capacity, and susceptibility to environmental conditions. These challenges have prompted the exploration of innovative solutions for road subgrade soil stabilization. Our primary motivation stems from the limitations of conventional techniques and the pressing need to address issues like resource exploitation and environmental pollution. Geopolymers, specifically alkaline-activated materials, have emerged as a promising alternative for soil stabilization. This research investigates the effects of geopolymer blended with rice husk ash (RHA) and fly ash (FA) on various geotechnical properties of natural and admixed black cotton soil. The soil is replaced with admixtures ranging from 0% to 30% of blended geopolymer by weight. The study provides a comprehensive analysis, focusing on quantifiable improvements in soil properties through numerical results. The investigations consistently reveal that the application of geopolymer as a soil stabilizer results in notable improvements in the geotechnical properties like index properties, strength properties, resistance to penetration (CBR), etc., of problematic soil. Comparative analysis with traditional methods underscores the superiority of the proposed geopolymer blend, showcasing its innovation, sustainability, and cost-effectiveness. The findings of this study contribute to the advancement of soil stabilization techniques, specifically in the context of geopolymer applications. For future work, this study suggests an in-depth exploration of geopolymer-stabilized soil's long-term durability and environmental impact. Additionally, further research could focus on optimizing the geopolymer blend ratios for varying soil types and environmental conditions.

Investigation of Subgrade Stabilization Life-Extending Benefits in Flexible Pavements Using a Non-Linear Mechanistic-Empirical Analysis

This paper investigates the effect of subgrade soil stabilization on the performance and life extension of flexible pavements. Several variables affecting soil stabilization were considered, including subgrade soil type (CL or CH), additive type and content (3, 6, and 9% of hydrated lime, 5, 10, and 15% of class C fly ash (CFA), and 5, 10, and 15% of cement kiln dust (CKD)), three stabilization thicknesses (15, 30, and 45 cm), and four pavement sections with varying thicknesses. The effects of these variables were investigated using four different damage mechanisms, including the fatigue life of the asphalt concrete (AC) and stabilized subgrade layers, the crushing life of the stabilized subgrade soil, and the rutting life of the pavement, using a non-linear mechanistic-empirical methodology. The results suggest that the optimum percentage that maximizes the pavement life occurs at 3% of lime for subgrade soil type CL, 6% of lime for subgrade type CH, and 15% of CFA and CKD for both subgrade soil types. The maximum pavement life increase occurred in the section with the lowest thickness and the highest stabilization thickness, which was 1890% for 3% of lime in the CL subgrade and 568% for 6% of lime in the CH subgrade. The maximum increase in the pavement life of subgrade stabilization with 15% of CFA was 2048% in a CL subgrade, and 397% in a CH subgrade, and life extension due to subgrade stabilization with 15% of CKD was 2323% in a CL subgrade and 797% in a CH subgrade.

Subgrade Stabilization with Ca (OH)2 Lime to Improve the Physical and Mechanical Properties of Soil (Case Study: The National Road Trengguli – Bts. Kab. Demak/Kudus)

Subgrade Stabilization with Ca (OH)2 Lime to Improve the Physical and Mechanical Properties of Soil (Case Study: The National Road Trengguli – Bts. Kab. Demak/Kudus)

Subbase stabilization with fly ash

Due to increased activities in civil engineering, and especially in the transport infrastructure, and thus an increase in the use of additional construction materials, innovative solutions are needed in finding alternative materials for the preservation of natural resources. One of the solutions for preserving natural building materials is the application of recycled material, which will also meet the required standards in civil engineering. In the transport infrastructure, there is a great opportunity for the use of recycled material, starting from the subbase, through the embankment and all the way to the superstructure and the concrete structures. One of the recycled materials that can be used in construction is fly ash. Fly ash is the most promising waste material when it comes to the wide range of applications in construction. Fly ash is obtained by burning coal in thermal power plants to produce electricity. Due to variations in the composition and characteristics of fly ash, several divisions and classifications have been created. One of the main classifications is according to the American standard ASTM C 618-05 where it is divided into class C and class F fly ash. This research aims to investigate the application of fly ash for subgrade stabilization and to determine the difference from a financial and environmental perspective for the application of fly ash compared to natural stone aggregate. The main research was carried out in connection with the increased use of natural stone aggregate, which appeared as a need during the rehabilitation of state road R1206, section Karpalak - Zelino. Apart from the use of large quantities of stone aggregate for the stabilization of the subgrade, it also had an impact on the financial framework for the realization of the road project. In Macedonia, an analysis of the chemical composition of 4 samples of fly ash obtained in REC Bitola was carried out. From the obtained results, it can be concluded that it belongs to the classification of F-class fly ash and with the use of an activator (lime or cement) it can be used in the stabilization of the subgrade.

Cement Stabilization of soft soil subgrade and Cost Analysis

The soft soil when present in subgrade creates a lot of problem in highways. Due to soft soil subgrade, the rutting is predominant cause of flexible pavement failure all around the world. This kind of soil is either replaced or modified prior to construction of other layers of road to minimize the formation of rut. This study deals with stabilization of soft soil subgrade by cement. The sample was collected from a depth around existing road subgrade. A series of laboratory tests on untreated soil sample was first done to determine the competency of soil as a subgrade layer followed by preparation of sample with varying stabilizer content i.e. 4%, 6% and 8% cement by weight of dry soil, to determine the optimum stabilizer content. Samples with varying cement content were also prepared for California Bearing Ratio (hereafter, CBR) and Unconfined Compressive Strength (hereafter, UCS)with different curing periods i.e. 7 days for CBR and 3, 7, 14 and 28 days for UCS. UCS test on these sample showed a significant improvement over the values of natural soil without stabilizer. CBR showed a similar trend and the resulting modified soil was competent enough to be used as a subgrade for heavy traffic condition. The pavement was modelled using Kenpave for 30 and 50 million standard axle (msa) traffic intensity to determine the ideal pavement section for two types of pavement used in this study. In addition, the cost of construction for replacement method and for cement stabilization are determined using norms of Department of Road and District rate of Kathmandu and are compared. The cement stabilized soil with optimum content is found to be cheaper than conventional method of replacement.

Gypsum and rice husk ash for sustainable stabilization of forest road subgrade

Forest roads are crucial for economic development and resource accessibility, especially in regions with extensive wood demand driven by construction growth. These roads require consistent maintenance to prevent structural issues, even though they experience lower traffic. Traditionally, gypsum has been used for soil stabilization due to its cation exchange capability with clay minerals and flocculation properties. However, its water solubility in wet conditions necessitates innovative solutions. This study explores a novel approach by combining gypsum with rice husk ash (RHA), an abundant agricultural waste, to address the challenges posed by expansive and low-bearing clay soils in forest road construction. In this study, an expansive soil with high plasticity and swelling potential is treated with varying combinations of RHA (5–20%) and gypsum (2–6%), followed by curing for 7, 15 and 30 days. Mechanical property tests revealed reduced plasticity and swelling pressure, alongside increased unconfined compressive strength. Microscopic analysis illustrated the formation of calcium silicate hydrate (CSH) and calcium aluminosilicate hydrate (CAH) gels, which possibly contributes to improved stability. This research underscores the potential of sustainable soil stabilization using gypsum and RHA synergy to fortify forest roads against expansive clay soil challenges, promoting eco-friendly and resilient infrastructure solutions.

Advancements in the Evolution of Engineering Characteristics and Reinforcement Technologies for Subgrade Silt.

Technical challenges associated with the treatment of silt subgrades frequently arise in coastal and river delta areas. Given the importance of environmental sustainability, the selection of efficient, cost-effective, and eco-friendly techniques for silt subgrade stabilization is paramount. While recycled polyester fibers primarily sourced from discarded polyester bottles have not yet been systematically employed in silt subgrade reinforcement, their potential is considerable. This paper offers a comprehensive review of the existing literature on the microstructural, physicochemical, and mechanical properties of silt, summarizing prior advancements in silt stabilization methodologies. Building upon this foundation, we introduce a novel approach utilizing recycled polyester fibers for silt subgrade improvement, outlining both its application prospects and challenges, which require further investigation. The findings of this study serve as a robust scientific foundation for the broader adoption and engineering implementation of this technology.

Effect of Composite Portland Cement for Subgrade Stabilization and the Effect on Unsoaked CBR Value

Soil is a material that has an essential role in construction. Soils that have low bearing capacity require soil improvement. One method of soil improvement is soil stabilization using composite portland cement. Based on the results of the Dynamic Cone Penetrometer (DCP) test, the location in this study, namely Cibingbin village, Pandeglang Regency, has a bearing capacity of 2.67%, meaning that the soil at this location needs to be repaired. This study aimed to determine the effect of portland cement on physical properties and unsoaked CBR values. Variations of portland cement used were 0%, 4%, 6%, and 8%, with curing times of 0 days and seven days. The results showed that based on the unified soil classification system (USCS), the soil classification was in the CH category (inorganic clay with high plasticity, fat clay) and the maximum CBR value was obtained at 8% Portland cement variety at seven days curing time, namely 13.23%.

Effect of sandstone slurry waste on the geotechnical properties of clay subgrade

Sustainability in clayey soil subgrade stabilization has become an emerging topic worldwide. The voluminous generation of sandstone slurry waste from the sandstone cutting and processing industries endangers the environment and human health. The present research investigated how such geotechnical characteristics of the clay soil subgrade were impacted by the addition of sandstone slurry waste (SSW) produced during the cutting and processing of sandstone. Sandstone slurry waste was dried for this experimental analysis and added to the clayey soil. Sandstone slurry waste was added in proportion from 0% to 35% (by dry weight) at intervals of 5% in clay soil, and mixtures were assessed based on how well their geotechnical properties have been improved. Atterberg's limits, compaction, and California bearing ratio (CBR) tests were conducted on the untreated clay and SSW-clay composites to evaluate the soil subgrade's physical properties and strength parameters. The experimental results revealed that incorporating 25% sandstone slurry waste by dry weight in clayey soil improves the maximum dry unit weight (MDUW), workability, and strength of clayey soil. The result of the CBR test showed that the CBR values of subgrade material enhanced with the addition of SSW. The improvement in treated composites was 69.79% and 68.27% for soaked and unsoaked conditions, respectively, at 25% SSW dose. The present experimental study shows that SSW-clay composite containing 25% SSW can treat the clayey soil subgrade.

Moisture stabilization of embankment subgrade with capillary barrier cover under dry and rainy weathers

Water loss from subgrade soil subjected to dry weather is possible to cause pavement desiccation cracking. On the contrary, intruded water will cause pavement failures because of the wetting swelling or collapsing of the subgrade soils. Therefore, avoiding the excessive fluctuations of the soil moisture in subgrade soils could increase the service life of the pavement. In this paper, the capillary barrier cover (CBC), consisting of the overlying fine-grained layer and the underlying coarse-grained layer, was newly used to maintain moisture stabilization of embankment subgrade under dry and rainy weathers. A group of physical model experiments were conducted to investigate the availability of this method. The results suggest that the CBC laid on the subgrade slope can effectively resist the moisture releasing from the subgrade during drying process, which is rarely reported and fully investigated at present. Meanwhile, the fine layer of CBC with low thermal conductivity can maintain a relatively stable temperature field, which is beneficial to uniform the moisture in subgrade. On the other hand, the CBC can also prevent water infiltration into subgrade during rainfall, even though cracks developed in the fine layer of CBC. Comparing to the subgrade without CBC, that subgrade with CBC has a more stable moisture field and a better performance under climatic variations.

Experimental Study on Subgrade Stabilization Using Geogrid and Perlite

Abstract: This paper presents the summary of experimental program to evaluate the soil stabilized with perlite and the geogridreinforcement. Due to its pozzolanic properties, perlite, a glassy volcanic rock, may be utilised as a stabilising agent. The standard California bearing ratio (CBR) laboratory tests were performed on the soil samples with various combinations of perlite and single layer of geogrid reinforcement placed at various height. The laboratory experiments were undertaken to investigate the impact of using perlite (0%, 10%, 20%, 30%) and geogrid (single layer of geogrid reinforcement placed at H/2, 3H/4 and H/4). The effect of geogrid reinforcement with respect to the position and varying contents of perlite on the strength behaviour of subgrade soil has been examined. Furthermore, the test was carried out by optimum percentage of perlite with geogrid placed at optimum height. Results of the current study indicate that there is a significant increase in CBR values for subgrade soil stabilized with perlite and reinforced with geogrid. Maximum CBR value was observed in the soil sample reinforced with single geogrid layer placed at H/4 (where H is height of CBR mould) with 20% perlite