Communications on Applied Nonlinear Analysis ISSN: 1074-133X Vol 32 No. 9s (2025) 1563 https://internationalpubls.com Comparative Study of Geotechnical Properties of Fly Ash and Bio Soil Mixed with Low Plastic Clay Shubhra Upadhyay1*, Ruchin Agarwal2, Pratyush3, and Som Pal Gangwar4 1Post Graduate Scholar (*Corressponding author), Department of Civil Engineering, Kamla Nehru Institute of Technology, Sultanpur, Uttar Pradesh, 228001, India; Email: shubhra.upadhyaya27@gmail.com 2Assistant Professor, Department of Civil Engineering, Kamla Nehru Institute of Technology, Sultanpur, Uttar Pradesh, 228001, India; Email: ruchin@knit.ac.in 3Research Scholar, Department of Civil Engineering, Kamla Nehru Institute of Technology, Sultanpur, Uttar Pradesh, 228001, India; Email: pratyushjeet067@gmail.ac.in 4Associate Professor, Department of Electronics Engineering, Kamla Nehru Institute of Technology, Sultanpur, Uttar Pradesh, 228001, India; Email: sompalgangwar @knit.ac.in Article History: Received: 12-01-2025 Revised: 15-02-2025 Accepted: 01-03-2025 Abstract: Bio soil is a byproduct obtained from the biomining of legacy waste, which typically contains over 50% of this inert material. Currently, its primary applications are limited to agriculture and filling low-lying areas. However, since bio soil is considered a waste material, this study explores its potential use in geotechnical structures, particularly as a subgrade material for highways. Fly ash is commonly used as a filling or subgrade material in highways and expressways. This research investigates whether bio soil can serve a similar purpose. For designing subgrades, the California Bearing Ratio (CBR) and compaction characteristics are crucial properties. This study compares the geotechnical properties of fly ash with those of a mixture of bio soil and low plastic clay. Laboratory tests were conducted to evaluate the compaction characteristics and CBR values of the bio soil-clay mixtures, focusing on the effect of different mixing ratios on strength improvement. Proctor compaction tests were used to analyze the compaction behavior, while CBR tests were conducted to assess strength characteristics. The study examined the impact of adding varying proportions of low plastic clay (0%, 20%, 40%, 60%, and 80%) to bio soil. Results showed that the optimal improvement in CBR and Maximum Dry Density (MDD) was achieved with a 60:40 ratio of bio soil to clay when compared to fly ash. Consequently, the findings suggest that bio soil, despite being a waste product, can be effectively utilized as a subgrade material in highways when mixed with low plastic clay. Keywords: Legacy Waste, Bio soil, Fly ash, Clay mailto:ruchin@knit.ac.in mailto:pratyushjeet067@gmail.ac.in mailto:sompalgangwar@knit.ac.in Communications on Applied Nonlinear Analysis ISSN: 1074-133X Vol 32 No. 9s (2025) 1564 https://internationalpubls.com 1 Introduction Many developing nations struggle with proper Municipal Solid Waste (MSW) management, often resorting to open dumping due to insufficient resources and lack of governmental support. For instance, in India, more than 90% of MSW ends up in open dumpsites [1]. This practice has led to urban areas being overwhelmed by overflowing waste sites containing substantial amounts of accumulated refuse. These locations typically lack proper infrastructure to effectively handle the liquid and gaseous waste decomposition products [2]. As a consequence, harmful substances are released into the environment, contaminating soil, air, and water sources, and creating significant health hazards [3]. The expansion of urban areas in India has resulted in waste disposal sites becoming incorporated within city limits, negatively impacting public health, environmental quality, and urban aesthetics [4]. The increasing population has heightened the need for landfill space to accommodate MSW, presenting sustainability challenges due to the constrained capacity of urban land [5]. Research indicates that legacy waste dumpsites occupy more than 10,000 hectares of urban land, creating substantial challenges for urban local bodies and municipal corporations in managing waste disposal safely [6]. In response to these issues, the Indian government initiated the Swachh Bharat Mission (SBM) to enhance public health and sanitation. A key component of this program is the remediation of abandoned dumpsites through Landfill Biomining (LFBM), also referred to as landfill mining. This process involves digging up, stabilizing, and sorting waste into various recyclable materials. The Central Statistics Office (CSO, 2021) reports that India produces about 152,076 metric tonnes of MSW daily, with approximately 98% being collected. Roughly 37% of this waste undergoes treatment, while the remainder is sent to landfills or dumpsites. Nevertheless, the majority of these sites have surpassed their capacity but continue to function due to limited space and other challenges [7]. Moreover, these waste sites present considerable environmental hazards, such as contamination of air and water, due to their lack of proper management and sanitary controls. Considering these issues, it is essential to investigate methods for repurposing the accumulated waste in these dumpsites. The stockpiled refuse at these locations comprises various materials, including plastics, wood, textiles, metals, glass, stone, and others, which can be utilized as secondary resources. A substantial portion of this waste consists of a soil-like substance referred to as the fine fraction (FF) or bio soil. This material is composed of decomposed organic matter, soil particles, sediment, woody debris, and other inert components. Bio soil constitutes approximately 40% to 80% of the total waste in landfills, varying based on the cut-off diameter. However, the potential reuse of this material is complicated by the presence of contaminants such as micro plastics, heavy metals, and organic pollutants. The use of bio soil as a building material presents an opportunity to recycle waste resources back into the human-constructed material cycle, aligning with circular economy objectives in developing nations. This strategy can simultaneously aid in the restoration of dumpsites while addressing the increasing need for construction materials in urban environments. The objective of this research is to examine the geotechnical characteristics of bio soil to determine its potential as a construction material. Various combinations of bio soil and other soil types will be tested to identify the optimal blend for construction purposes. The study will also compare the geotechnical properties of these bio soil mixtures with those of fly ash, a material frequently Communications on Applied Nonlinear Analysis ISSN: 1074-133X Vol 32 No. 9s (2025) 1565 https://internationalpubls.com employed in subgrade construction for highways and other infrastructure. Essential tests, including the California Bearing Ratio (CBR) and Proctor compaction tests, will be conducted to evaluate the strength and compaction qualities of the bio soil mixtures. Through comparison with fly ash, this investigation aims to ascertain whether bio soil can serve as a viable alternative in subgrade construction. If proven successful, this approach could provide a sustainable solution to address waste management issues and construction material shortages, thereby contributing to environmental conservation and urban growth. 2 Sample preparation and materials used An experimental investigation has been done using Bio soil, soil (low plastic clay) & fly ash. Bio soil is added to soil (low plastic clay - CL soil) in a varying percentage (100%, 80%, 60%, 40% & 20% by dry weight) and compared with geotechnical properties of Fly Ash respectively. Total 6 samples are prepared by mixing Bio soil and low plastic clay and have been compared with Fly ash after investigating the geotechnical properties of both. Table 2.1 shows different samples. Table 2.1 Details of Samples Sr. No. Details of Sample Name of Sample Nomenclature 1. Bio soil Sample 1 (100:0) S1 2. Soil Sample 2 (0:100) S2 3. 80% Bio soil + 20% CL soil Sample 3 (80:20) S3 4. 60% Bio soil + 40% CL soil Sample 4 (60:40) S4 5. 40% Bio soil + 60% CL soil Sample 5 (60:40) S5 6. 20% Bio soil + 80% CL soil Sample 6 (20:80) S6 7. Fly Ash Sample 7 (FA) S7 2.1 Materials Used The materials utilized in this study are as follows: 2.1.1 Bio Soil The Bio soil used in this study is sourced from Biomining work, Baswar Dumpsite, Naini, Prayagraj, Uttar Pradesh. Fig.2.2 shows the particle size distribution (PSD) analysis of used Bio soil following IS: 2720-Part-4-1975. According to the Indian Standard Classification System (ISCS), this soil is classified as Poorly Graded Sand (SP). Figure 2.1 Bio Soil Communications on Applied Nonlinear Analysis ISSN: 1074-133X Vol 32 No. 9s (2025) 1566 https://internationalpubls.com Table 2.2 Properties of Bio Soil Specific Gravity 2.042 Coefficient of Curvature, Cc 0.7097 Coefficient of uniformity, Cu 10.502 Classification Poorly Graded Sand (SP) D50(mm) 1.089 Water content (%) 25.12 Maximum dry Density (MDD), γd (g/cc) 1.37 Optimum Moisture Content (OMC), % 25.12 2.1.2 Soil The Soil used was sourced from Kurebhar, Sultanpur, Uttar Pradesh. Fig.4.3 shows the particle size distribution (PSD) analysis of used soil following IS: 2720-Part-4-1975. According to the Indian Standard Classification System (ISCS), this soil is classified as Low Plasticity Clay (CL). Figure 2.3 Soil Communications on Applied Nonlinear Analysis ISSN: 1074-133X Vol 32 No. 9s (2025) 1567 https://internationalpubls.com Table 2.3 Soil properties Specific Gravity 2.742 Liquid Limit, WL (%) 30 Plastic Limit, WP (%) 23 Plasticity Index, IP (%) 7 Classification Low Plastic Clay (CL) Water content (%) 11.45% 2.1.3 Fly Ash The used Fly Ash was sourced from NTPC Tanda, Uttar Pradesh. Fly ash is fine, powdery material that is a byproduct of burning coal in power plants. It is carried away in the exhaust gases and collected using electrostatic precipitators or other methods. Fly ash is commonly used as a supplementary cementitious material in concrete and construction due to its pozzolanic properties. Figure 3.1 Fly Ash Communications on Applied Nonlinear Analysis ISSN: 1074-133X Vol 32 No. 9s (2025) 1568 https://internationalpubls.com 3 Results and Discussions 3.1 Specific Gravity Figure 3.1 Trend of Specific Gravity From figure 3.1 following result is deduced, • For all types of the mixture samples studied, the specific gravity of samples is increasing as proportion of CL soil in Bio soil is increasing 3.2 Compaction Characteristics Figure 3.1 Trend of MDD From figure 3.2 following results are deduced, • For all types of the mixtures studied, the MDD increases as the proportion of CL soil increases (upto 60%). • It is also found that, MDD of Sample 5 (40:60) is more than MDD of Fly Ash. 2.041 2.742 2.130 2.231 2.368 2.656 2.297 0.000 0.500 1.000 1.500 2.000 2.500 3.000 S1 S2 S3 S4 S5 S6 S7 S p ec if ic G ra v it y Samples Trend of Specific Gravity 1.49 1.76 1.58 1.65 1.70 1.61 1.3 0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00 S1 S2 S3 S4 S5 S6 S7 M D D ( g /c c) Samples Trend of MDD Communications on Applied Nonlinear Analysis ISSN: 1074-133X Vol 32 No. 9s (2025) 1569 https://internationalpubls.com Figure 3.2 Trend of OMC From the figure 3.3, shows the variation of OMC of various proportions of Bio soil & CL soil. Following figure 3.4 shows comparison of MDD of Bio soil, CL soil, Fly Ash & different samples prepared by mixing bio soil and CL soil. From figure, it is found that, bio soil when mixed with CL soil in proportion of 40:60 respectively, then its MDD is more than that of Fly Ash & OMC of it is also less than that of Fly Ash. Figure 3.3 Comparison Proctor test of different Samples 17.91 14.62 17.09 16.78 16.00 17.07 17.97 0.00 2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00 S1 S2 S3 S4 S5 S6 S7 O M C ( % ) Samples Trend of OMC 0.80 1.00 1.20 1.40 1.60 1.80 2.00 0.00 5.00 10.00 15.00 20.00 25.00 30.00 D ry D en si ty ( g /c c) Moisture Content (%) Comparison of Proctor Test of Different Samples Proctor Test Fly ash, S7 Proctor Test, S5 (40:60) Proctor Test, S4 (60:40) Proctor test, S3(80:20) Proctor Test, S1 (100:0) Proctor Test, S6 (20:80) Proctor Test, S2 (0:100) Communications on Applied Nonlinear Analysis ISSN: 1074-133X Vol 32 No. 9s (2025) 1570 https://internationalpubls.com 3.3 California Bearing Ratio (CBR) Test a) CBR of Unsoaked Samples Figure 3.4 Trend of CBR values of different Unsoaked Samples From figure 3.5 following results are deduced, • For all types of the mixtures studied, the CBR increases as the proportion of CL soil increases (upto 60%). • It is also found that, CBR of Sample 5 (40:60) is more than CBR of Fly Ash. Figure 3.5 Comparison of Load Vs Penetration Curves of different Unsoaked Samples Above figure 3.6 shows comparison of CBR of Unsoaked Bio soil, CL soil, Fly Ash & different samples prepared by mixing bio soil and CL soil. From figure, it is found that, bio soil when mixed with CL soil in proportion of 40:60 respectively, then its CBR is more than that of Fly Ash. 4.27 8.08 5.9 8.64 9.75 7.89 7.43 0 2 4 6 8 10 12 S1 S2 S3 S4 S5 S6 S7 C B R (% ) Samples Trend of CBR(Unsoaked) 0 100 200 300 400 500 600 700 0 2 4 6 8 10 12 14 16 L o a d ( k g ) Penetration (mm) Comparison of CBR of Unsoaked Samples CBR, S1(100-0) CBR, S3 (80:20) CBR, S4(60:40) CBR, S5(40:60) CBR, S6(20:80) CBR,S7(Fly Ash) CBR, S2 (0:100) Communications on Applied Nonlinear Analysis ISSN: 1074-133X Vol 32 No. 9s (2025) 1571 https://internationalpubls.com b) CBR of Soaked Samples Figure 3.6 Trend of CBR values of different Soaked Samples From figure 3.7 following results are deduced, • For all types of the mixtures studied, the CBR increases as the proportion of CL soil increases (upto 60%). • It is also found that, CBR of Sample 5 (40:60) is more than MDD of Fly Ash. Figure 3.7 Comparison of Load Vs Penetration Curves of different Soaked Samples Above figure 3.8 shows comparison of CBR of Soaked Bio soil, CL soil, Fly Ash & different samples prepared by mixing bio soil and CL soil. From figure, it is found that, bio soil when mixed with CL soil in proportion of 40:60 respectively, then its CBR is more than that of Fly Ash. 5.57 9.94 7.89 11.15 12.63 10.22 9.66 0 2 4 6 8 10 12 14 S1 S2 S3 S4 S5 S6 S7 C B R (% ) Samples Trend of CBR(Soaked) 0 200 400 600 800 1000 0 2 4 6 8 10 12 14 16 L o a d ( k g ) Penetration(mm) Comparison of CBR of Soaked Sample CBR, S7 (Fly Ash) CBR, S6 (20:80) CBR, S5 (40:60) CBR, S4(60:40) CBR, S3 (80:20) CBR, S1 (100:0) CBR, S2 (0:100) Communications on Applied Nonlinear Analysis ISSN: 1074-133X Vol 32 No. 9s (2025) 1572 https://internationalpubls.com 3.4 COMPARISON OF RESULTS Following table shows the comparison of geotechnical properties of bio soil, CL soil, Fly ash and Sample 5 Table 3.1 Comparison of Properties 4 Conclusions A series of the following tests: Specific Gravity test, Standard Compaction test & California Bearing Ratio tests were carried out on Bio soil, Soil, fly ash & different mixtures of bio soil & soil (in the proportions (80:20), (60:40), (40:60), (20:80); to explore the impact of soil variation in Bio soil and elucidate the trends of change in these characteristics concerning fly ash, an investigation is conducted. Drawing from the results and discussions derived from the Specific Gravity test, Standard Compaction test, and California Bearing Ratio tests, the following conclusions are drawn: 1. For Bio-soil only a. The specific gravity of bio-soil used in the work is 2.041 and has been classified as Poorly Graded Sand (SP) with OMC & MDD are 17.91% & 1.49g/cc b. The value of Unsoaked & Soaked CBR for bio soil is 4.27% & 5.57% respectively 2. For CL soil only a. The specific gravity of soil used in the work is 2.742 and has been classified as low plastic clay (CL) with OMC & MDD are 14.63% & 1.76g/cc b. The value of Unsoaked & Soaked CBR for soil is 8.08% & 9.94% respectively 3. For Fly ash only a. The specific gravity of fly ash used in the work is 2.297 with OMC & MDD are 17.97% & 1.30g/cc. b. The value of Unsoaked & Soaked CBR for fly ash is 7.43% & 9.66% respectively 4. For Bio soil mixed with CL soil in different proportions a. For all types of the proportions studied, the specific gravity increases as the proportion of clay particles increases in bio soil because bio soil particles are replaced by clay particles. b. For all types of the proportions studied, the maximum dry unit weight increases as the proportion of soil (upto 60%) increases and decreases for 80% soil. Also, it has been observed and investigated that MDD of Sample 5 (40:60) is more than that of Fly Ash. Communications on Applied Nonlinear Analysis ISSN: 1074-133X Vol 32 No. 9s (2025) 1573 https://internationalpubls.com c. For all types of the proportions studied, it has been found that the CBR of Unsoaked samples increases as the proportion of soil (upto 60%) increases and it gets decreased for 80% soil. Also, it has been seen that CBR of Unsoaked Sample 5 (40:60) is more than that of Fly Ash. d. For all types of the proportions studied, it is investigated that the CBR of Soaked samples increases as the proportion of soil (upto 60%) increase and decreases for 80% soil. Also, it has been investigated that the CBR of Soaked Sample 5 (40:60) is more than that of Fly Ash. 5. From the results, it is concluded that bio soil which is a waste material has also its utility in Subgrade of highways when it is mixed with soil. 6. Bio soil possesses good subgrade properties than fly ash when it is mixed with soil. References [1] S. Vaibhav, S. A. Ismail, P. Singh, and R. P. Singh, “Urban solid waste management in the developing world with emphasis on India: challenges and opportunities.” Reviews in Environmental Science and Biotechnology., vol. 14(2), pp. 317-337, Jun. 2015. [2] S. Anchal, A. K. Gupta, and R. Ganguly, “Impact of open dumping of municipal solid waste on soil properties in mountainous region.” Journal of Rock Mechanics and Geotechnical Engineering ., vol. 10(4), pp. 725-739, Aug. 2018. [3] A. K. Biswas, S. Kumar, S. S. Babu, J. K. Bhattacharyya, and T. Chakrabarti, “Studies on environmental quality in and around municipal solid waste dumpsite.” Resources Conservation and Recycling., vol. 55(2), pp.129-134, Dec. 2010. [4] A. E. Peter, S. M. S. Nagendra, and I. M. Nambi, “Environmental burden by an open dumpsite in urban India.” Waste management., vol. 85, pp. 151-163, Feb. 2019. [5] Y. Pujara, P. Pathak, A. Sharma, and J. Govani, “Review on Indian Municipal Solid Waste Management practices for reduction of environmental impacts to achieve sustainable development goals.” Journal of environmental management., vol. 248, Oct. 2019. [6] Municipal solid waste management manual (MSWM), Part-II: Annexure1. MoUD. 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